Green Environment

Cloud Radiative Forcing

noreply@blogger.com (Gen777) — Mon, 06 Jun 2011 15:06:00 +0000

Cloud Radiative Forcing is the difference between the radiation budget components for average cloud conditions and cloud-free conditions. Much of the interest in cloud forcing relates to its role as a feedback process in the present period of global warming.

All global climate models used for climate change projections include the effects of water vapor and cloud forcing. The models include the effects of clouds on both incoming (solar) and emitted (terrestrial) radiation.

Clouds increase the global reflection of solar radiation from 15 to 30%, reducing the amount of solar radiation absorbed by the Earth by about 44 W/m². This cooling is offset somewhat by the greenhouse effect of clouds which reduces the outgoing longwave radiation by about 31 W/m². Thus the net cloud forcing of the radiation budget is a loss of about 13 W/m². If the clouds were removed with all else remaining the same, the Earth would gain this last amount in net radiation and begin to warm up. These numbers should not be confused with the usual radiative forcing concept, which is for the change in forcing related to climate change.

Without the inclusion of clouds, water vapor alone contributes between 36-70% of the greenhouse effect on Earth. When considering water vapor and clouds together, the contribution is between 66-85%. The ranges come about because there are two ways to compute the influence of water vapor and clouds: the lower bounds are the reduction in the greenhouse effect if water vapor and clouds are removed from the atmosphere leaving all other greenhouse gases unchanged, while the upper bounds are the greenhouse effect introduced if water vapor and clouds are added to an atmosphere with no other greenhouse gases. The two values differ because of overlap in the absorption and emission by the various greenhouse gases. Trapping of the long-wave radiation due to the presence of clouds reduces the radiative forcing of the greenhouse gases compared to the clear-sky forcing. However, the magnitude of the effect due to clouds varies for different greenhouse gases. Relative to clear skies, clouds reduce the global mean radiative forcing due to CO₂ by about 15%, that due to CH₄ and N₂O by about 20%, and that due to the halocarbons by up to 30%. Clouds remain one of the largest uncertainties in future projections of climate change by global climate models, owing to the physical complexity of cloud processes and the small scale of individual clouds relative to the size of the model computational grid.

Uses of Carbon Tetrachloride

noreply@blogger.com (Gen777) — Sat, 04 Jun 2011 14:20:00 +0000

In the 20th century, carbon tetrachloride was widely used as a dry cleaning solvent, as a refrigerant, and in lava lamps.

In 1910, The Pyrene Manufacturing Company of Delaware filed a patent for a using carbon tetrachloride to extinguish fires. The liquid vaporized and extinguished the flames by inhibiting the chemical chain reaction of the combustion process (it was an early 20th century presupposition that the fire suppression ability of carbon tetrachloride relied on oxygen removal.) In 1911, they patented a small, portable extinguisher that used the chemical. This consisted of a brass bottle with an integrated handpump which was used to expel a jet of liquid towards the fire. As the container was unpressurized, it could be easily refilled after use. Carbon tetrachloride was suitable for liquid and electrical fires and the extinguisers were often fitted to motor vehicles.

One specialty use of carbon tetrachloride was by stamp collectors to reveal watermarks on the backs of postage stamps without damaging the stamp. A small amount of the liquid was placed on the back of a stamp sitting in a black glass or obsidian tray. The letters or design of the watermark could then be clearly detected.

However, once it became apparent that carbon tetrachloride exposure had severe adverse health effects, safer alternatives such as tetrachloroethylene were found for these applications, and its use in these roles declined from about 1940 onward. The fact that high temperatures cause it to react to produce phosgene made it especially hazardous when used against fires. This reaction also caused a rapid depletion of oxygen. Carbon tetrachloride persisted as a pesticide to kill insects in stored grain, but in 1970, it was banned in consumer products in the United States.

Prior to the Montreal Protocol, large quantities of carbon tetrachloride were used to produce the freon refrigerants R-11 (trichlorofluoromethane) and R-12 (dichlorodifluoromethane). However, these refrigerants are now believed to play a role in ozone depletion and have been phased out. Carbon tetrachloride is still used to manufacture less destructive refrigerants. Carbon tetrachloride has also been used in the detection of neutrinos.

Carbon tetrachloride is one of the most potent hepatotoxins (toxic to the liver), and is widely used in scientific research to evaluate hepatoprotective agents.

Reactivity

Carbon tetrachloride has practically no flammability at lower temperatures. Under high temperatures in air, it forms poisonous phosgene.

Because it has no C-H bonds, carbon tetrachloride does not easily undergo free-radical reactions. Hence, it is a useful solvent for halogenations either by the elemental halogen, or by a halogenation reagent such as N-bromosuccinimide (these conditions are known as Wohl-Ziegler Bromination).

In organic chemistry, carbon tetrachloride serves as a source of chlorine in the Appel reaction.

Solvent

It is used as a solvent in synthetic chemistry research, but because of its adverse health effects, it is no longer commonly used, and chemists generally try to replace it with other solvents. It is sometimes useful as a solvent for infrared spectroscopy, because there are no significant absorption bands > 1600 cm⁻¹. Because carbon tetrachloride does not have any hydrogen atoms, it was historically used in proton NMR spectroscopy. However, carbon tetrachloride is toxic, and its dissolving power is low. Its use has been largely superseded by deuterated solvents. Use of carbon tetrachloride in determination of oil has been replaced by various other solvents, such as tetrachloroethylene.

Carbon Tetrachloride Synthesis

noreply@blogger.com (Gen777) — Sat, 04 Jun 2011 14:19:00 +0000

The production of carbon tetrachloride has steeply declined since the 1980s due to environmental concerns and the decreased demand for CFCs, which were derived from carbon tetrachloride. In 1992, production in the U.S.-Europe-Japan was estimated at 720,000 tonnes.

Carbon tetrachloride was originally synthesised by the French chemist Henri Victor Regnault in 1839 by the reaction of chloroform with chlorine, but now it is mainly produced from methane:

CH₄ + 4 Cl₂ → CCl₄ + 4 HCl

The production often utilizes by-products of other chlorination reactions, such as from the syntheses of dichloromethane and chloroform. Higher chlorocarbons are also subjected to "chlorinolysis:"

C₂Cl₆ + Cl₂ → 2 CCl₄

Prior to the 1950s, carbon tetrachloride was manufactured by the chlorination of carbon disulfide at 105 to 130 °C:

CS₂ + 3Cl₂ → CCl₄ + S₂Cl₂

Carbon Tetrachloride

noreply@blogger.com (Gen777) — Sat, 04 Jun 2011 14:17:00 +0000

Carbon tetrachloride, also known by many other names (notably, carbon tet in the cleaning industry, and as a Halon or Freon in HVAC, see Table for others) is the organic compound with the formula CCl₄. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent. It is a colourless liquid with a "sweet" smell that can be detected at low levels.

Both carbon tetrachloride and tetrachloromethane are acceptable names under IUPAC nomenclature.

In the carbon tetrachloride molecule, four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a central carbon atom by single covalent bonds. Because of this symmetrical geometry, CCl₄ is non-polar. Methane gas has the same structure, making carbon tetrachloride a halomethane. As a solvent, it is well suited to dissolving other non-polar compounds, fats and oils. It can also dissolve iodine. It is somewhat volatile, giving off vapors having a smell characteristic of other chlorinated solvents, somewhat similar to the tetrachloroethylene smell reminiscent of dry cleaners' shops.

Solid tetrachloromethane has 2 polymorphs: crystalline II below −47.5 °C (225.6 K) and crystalline I above −47.5 °C.

At −47.3 °C it has monoclinic crystal structure with space group C2/c and lattice constants a = 20.3, b = 11.6, c = 19.9 (.10⁻¹ nm), β = 111°. With a specific gravity greater than 1, carbon tetrachloride will be present as a dense nonaqueous phase liquid if sufficient quantities are spilled in the environment.

Exposure to high concentrations of carbon tetrachloride (including vapor) can affect the central nervous system, degenerate the liver and kidneys and may result (after prolonged exposure) in coma and even death. Chronic exposure to carbon tetrachloride can cause liver and kidney damage and could result in cancer. More information can be found in Material safety data sheets.

In 2008, a study of common cleaning products found the presence of carbon tetrachloride in "very high concentrations" (up to 101 mg m⁻³) as a result of manufacturers' mixing of surfactants or soap with sodium hypochlorite (bleach).

Carbon tetrachloride is also both ozone-depleting and a greenhouse gas. However, since 1992 its atmospheric concentrations have been in decline for the reasons described above (see also the atmospheric time-series figure). CCl₄ has an atmospheric lifetime of 85 years.

Chemical Processes of Carbon Sequestration

noreply@blogger.com (Gen777) — Wed, 01 Jun 2011 19:06:00 +0000

Chemical Processes of Carbon Sequestration.

Carbon, in the form of CO₂ can be removed from the atmosphere by chemical processes, and stored in stable carbonate mineral forms. This process is known as 'carbon sequestration by mineral carbonation' or mineral sequestration. The process involves reacting carbon dioxide with abundantly available metal oxides–either magnesium oxide (MgO) or calcium oxide (CaO)–to form stable carbonates. These reactions are exothermic and occur naturally (e.g., the weathering of rock over geologic time periods).

CaO + CO₂ → CaCO₃

MgO + CO₂ → MgCO₃

Calcium and magnesium are found in nature typically as calcium and magnesium silicates (such as forsterite and serpentinite) and not as binary oxides. For forsterite and serpentine the reactions are:

Mg₂SiO₄ + 2CO₂ = 2MgCO₃ + SiO₂

Mg₃Si₂O₅(OH)₄+ 3CO₂ = 3MgCO₃ + 2SiO₂ + 2H₂O

The following table lists principal metal oxides of Earth's crust. Theoretically up to 22% of this mineral mass is able to form carbonates.

Earthen Oxide	Percent of Crust	Carbonate	Enthalpy change (kJ/mol)
SiO₂	59.71
Al₂O₃	15.41
CaO	4.90	CaCO₃	-179
MgO	4.36	MgCO₃	-117
Na₂O	3.55	Na₂CO₃
FeO	3.52	FeCO₃
K₂O	2.80	K₂CO₃
Fe₂O₃	2.63	FeCO₃
	21.76	All Carbonates

These reactions are favored at low temperatures. This process occurs naturally over geologic time frames and is responsible for much of the Earth's surface limestone. The reaction rate can be made faster, for example by reacting at higher temperatures and/or pressures, or by pre-treatment, although this method requires additional energy.

CO₂ naturally reacts with peridotite rock in surface exposures of ophiolites, notably in Oman. It has been suggested that this process can be enhanced to carry out natural mineralisation of CO₂.

Industrial use

Traditional cement manufacture releases large amounts of carbon dioxide, but newly developed cement types from Novacem can absorb CO₂ from ambient air during hardening. A similar technique was pioneered by TecEco, which has been producing "EcoCement" since 2002.

In Estonia, oil shale ash, generated by power stations could be used as sorbents for CO₂ mineral sequestration. The amount of CO₂ captured averaged 60–65% of the carbonaceous CO₂ and 10–11% of the total CO₂ emissions.

Chemical scrubbers

Various carbon dioxide scrubbing processes have been proposed to remove CO₂ from the air, usually using a variant of the Kraft process. Carbon dioxide scrubbing variants exist based on potassium carbonate, which can be used to create liquid fuels, or on sodium hydroxide. These notably include artificial trees proposed by Klaus Lackner to remove carbon dioxide from the atmosphere using chemical scrubbers.

Ocean-related

Basalt storage

Carbon dioxide sequestration in basalt involves the injecting of CO₂ into deep-sea formations. The CO₂ first mixes with seawater and then reacts with the basalt, both of which are alkaline-rich elements. This reaction results in the release of Ca2+ and Mg2+ ions forming stable carbonate minerals.

Underwater basalt offers a good alternative to other forms of oceanic carbon storage because it has a number of trapping measures to ensure added protection against leakage. These measures include “geothermal, sediment, gravitational and hydrate formation.” Because CO₂ hydrate is denser than CO₂ in seawater, the risk of leakage is minimal. Injecting the CO₂ at depths greater than 2,700 meters (8,858 ft) ensures that the CO₂ has a greater density than seawater, causing it to sink.

One possible injection site is Juan de Fuca plate. Researchers at the Lamont-Doherty Earth Observatory found that this plate at the western coast of the United States has a possible storage capacity of 208 gigatons. This could cover the entire current U.S. carbon emissions for over 100 years.

Acid neutralisation

Adding crushed limestone or volcanic rock^] to oceans enhances the solubility pump, which naturally removes CO₂ from the atmosphere. Various other scientists have explored this technique, and suggested a variety of different bases that added to the ocean, increase CO₂ absorption.

Hydrochloric acid removal

Electrolysis removes hydrochloric acid from the ocean for neutralization with silicate minerals or rocks. Electrolysis may contribute to carbon addition to the ocean if not carefully managed.

Physical Processes of Carbon Sequestration

noreply@blogger.com (Gen777) — Wed, 01 Jun 2011 19:03:00 +0000

Physical Processes of Carbon Sequestration

Bio-energy with carbon capture and storage (BECCS)

BECCS refers to biomass in power stations and boilers that use carbon capture and storage.The carbon sequestered by the biomass would be captured and stored, thus removing carbon dioxide from the atmosphere.

This technology is sometimes referred to as bio-energy with carbon storage, BECS, though this term can also refer to the carbon sequestration potential in other technologies, such as biochar.

Burial

Burying biomass (such as trees) directly, mimics the natural processes that created fossil fuels. Landfills also represents a physical method of sequestration.

Biochar burial

Biochar is charcoal created by pyrolysis of biomass waste. The resulting material is added to a landfill or used as a soil improver to create terra preta. Biogenic carbon is recycled naturally in the carbon cycle. Pyrolysing it to biochar renders the carbon inert so that it remains sequestered in soil. Further, the soil encourages bulking with new organic matter, which gives additional sequestration benefit.

In the soil, the carbon is unavailable for oxidation to CO₂ and consequential atmospheric release. This is one technique advocated by prominent scientist James Lovelock, creator of the Gaia hypothesis. According to Simon Shackley, "people are talking more about something in the range of one to two billion tonnes a year."

The mechanisms related to biochar are referred to as bio-energy with carbon storage, BECS.

Ocean storage

River mouths bring large quantities of nutrients and dead material from upriver into the ocean as part of the process that eventually produces fossil fuels. Transporting material such as crop waste out to sea and allowing it to sink exploits this idea to increase carbon storage. International regulations on marine dumping may restrict or prevent use of this technique.

Subterranean injection

Carbon dioxide can be injected into depleted oil and gas reservoirs and other geological features, or can be injected into the deep ocean.

The first large-scale CO₂ sequestration project which began in 1996 is called Sleipner, and is located in the North Sea where Norway's StatoilHydro strips carbon dioxide from natural gas with amine solvents and disposed of this carbon dioxide in a deep saline aquifer. In 2000, a coal-fueled synthetic natural gas plant in Beulah, North Dakota, became the world's first coal using plant to capture and store carbon dioxide, at the Weyburn-Midale Carbon Dioxide Project.

CO₂ has been used extensively in enhanced crude oil recovery operations in the United States beginning in 1972. There are in excess of 10,000 wells that inject CO₂ in the state of Texas alone. The gas comes in part from anthropogenic sources, but is principally from large naturally occurring geologic formations of CO₂. It is transported to the oil-producing fields through a large network of over 5,000 kilometres (3,100 mi) of CO₂ pipelines. The use of CO₂ for enhanced oil recovery (EOR) methods in heavy oil reservoirs in the Western Canadian Sedimentary Basin (WCSB) has also been proposed. However, transport cost remains an important hurdle. An extensive CO₂ pipeline system does not yet exist in the WCSB. Athabasca oil sands mining that produces CO₂ is hundreds of kilometers north of the subsurface heavy oil reservoirs that could most benefit from CO₂ injection.

Biological Processes of Carbon Sequestration

noreply@blogger.com (Gen777) — Wed, 01 Jun 2011 18:58:00 +0000

Biological Processes of Carbon Sequestration. Biosequestration or carbon sequestration through biological processes affects the Global carbon cycle. Examples include major climatic fluctuations, such as the Azolla event, which created the current Arctic climate. Such processes created fossil fuels, as well as clathrate or limestone. By manipulating such processes, geoengineers seek to enhance sequestration.

Peat production

Peat bogs are a very important carbon store. By creating new bogs, or enhancing existing ones, carbon can be sequestered.

Forestry

Reforestation is the replanting of trees on marginal crop and pasture lands to incorporate carbon from atmospheric CO₂ into biomass. For this process to succeed the carbon must not return to the atmosphere from burning or rotting when the trees die. To this end, the trees must grow in perpetuity or the wood from them must itself be sequestered, e.g., via biochar, bio-energy with carbon storage (BECS) or landfill.

Agriculture

Globally, soils are estimated to contain approximately 1,500 gigatons of organic carbon, more than the amount in vegetation and the atmosphere.

Modification of agricultural practices is a recognized method of carbon sequestration as soil can act as an effective carbon sink offsetting as much as 20% of 2010 carbon dioxide emissions annually.

Carbon emission reduction methods in agriculture can be grouped into two categories: reducing and/or displacing emissions and enhancing carbon removal. Some of these reductions involve increasing the efficiency of farm operations (i.e. more fuel-efficient equipment) while some involve interruptions in the natural carbon cycle. Also, some effective techniques (such as the elimination of stubble burning) can negatively impact other environmental concerns (increased herbicide use to control weeds not destroyed by burning).

Reducing Emissions

Increasing yields and efficiency generally reduces emissions as well, since more food results from the same or less effort. Techniques include more accurate use of fertilizers, less soil disturbance, better irrigation, and crop strains bred for locally beneficial traits and increased yields.

Replacing more energy intensive farming operations can also reduce emissions. Reduced or no-till farming requires less machine use and burns correspondingly less fuel per acre. However, no-till usually increases use of weed-control chemicals and the residue now left on the soil surface is more likely to release its CO₂ to the atmosphere as it decays, reducing the net carbon reduction.

In practice, most farming operations that incorporate post-harvest crop residues, wastes and byproducts back into the soil provide a carbon storage benefit. This is particularly the case for practices such as field burning of stubble - rather than releasing almost all of the stored CO₂ to the atmosphere, tillage incorporates the biomass back into the soil where it can be absorbed and a portion of it stored permanently.

Enhancing Carbon Removal

All crops absorb CO₂ during growth and release it after harvest. The goal of agricultural carbon removal is to use the crop and its relation to the carbon cycle to permanently sequester carbon within the soil. This is done by selecting farming methods that return biomass to the soil and enhance the conditions in which the carbon within the plants will be reduced to its elemental nature and stored in a stable state. Methods for accomplishing this include:

Use cover crops such as grasses and weeds as temporary cover between planting seasons
Concentrate livestock in small paddocks for days at a time so they graze lightly but evenly. This encourages roots to grow deeper into the soil. Stock also till the soil with their hooves, grinding old grass and manures into the soil.
Cover bare paddocks with hay or dead vegetation. This protects soil from the sun and allows the soil to hold more water and be more attractive to carbon-capturing microbes.
Restore degraded land, which slows carbon release while returning the land to agriculture or other use.

Agricultural sequestration practices may have positive effects on soil, air, and water quality, be beneficial to wildlife, and expand food production. On degraded croplands, an increase of 1 ton of soil carbon pool may increase crop yield by 20 to 40 kilograms per hectare of wheat, 10 to 20 kg/ ha for maize, and 0.5 to 1 kg/ha for cowpeas.

The effects of soil sequestration can be reversed. If the soil is disrupted or tillage practices are abandoned, the soil becomes a net source of greenhouse gases. Typically after 15 to 30 years of sequestration, soil becomes saturated and ceases to absorb carbon. This implies that there is a global limit to the amount of carbon that soil can hold.

Many factors affect the costs of carbon sequestration including soil quality, transaction costs and various externalities such as leakage and unforeseen environmental damage. Because reduction of atmosperic CO₂ is a long-term concern, farmers can be reluctant to adopt more expensive agricultural techniques when there is not a clear crop, soil, or economic benefit. Governments such as Australia and New Zealand are considering allowing farmers to sell carbon credits once they document that they have sufficiently increased soil carbon content.

Ocean-related

Iron fertilization

Ocean iron fertilization is an example of such a geoengineering technique. Iron fertilization attempts to encourage phytoplankton growth, which removes carbon from the atmosphere for at least a period of time. This technique is controversial due to limited understanding its complete effects on the marine ecosystem, including side effects and possibly large deviations from expected behavior. Such effects potentially include release of nitrogen oxides, and disruption of the ocean's nutrient balance.

Urea fertilisation

Ian Jones proposes to fertilize the ocean with urea, a nitrogen rich substance, to encourage phytoplankton growth.

Australian company Ocean Nourishment Corporation (ONC) plans to sink hundreds of tonnes of urea into the ocean to boost CO₂-absorbing phytoplankton growth as a way to combat climate change. In 2007, Sydney-based ONC completed an experiment involving 1 tonne of nitrogen in the Sulu Sea off the Philippines.

Mixing layers

Encouraging various ocean layers to mix can move nutrients and dissolved gases around, offering avenues for geoengineering. Mixing may be achieved by placing large vertical pipes in the oceans to pump nutrient rich water to the surface, triggering blooms of algae, which store carbon when they die. This produces results somewhat similar to iron fertilization. One side-effect is a short-term rise in CO₂, which limits its attractiveness.

Carbon Sequestration

noreply@blogger.com (Gen777) — Wed, 01 Jun 2011 18:57:00 +0000

Carbon sequestration is "The process of removing carbon from the atmosphere and depositing it in a reservoir." When carried out deliberately, this may also be referred to as carbon dioxide removal, which is a form of geoengineering. The term carbon sequestration may also be used to refer to the process of carbon capture and storage, where carbon dioxide (CO₂) is removed from flue gases, such as on power stations, before being stored in underground reservoirs. The term may also refer to natural biogeochemical cycling of carbon between the atmosphere and reservoirs, such as by chemical weathering of rocks.

Carbon sequestration describes long-term storage of carbon dioxide or other forms of carbon to either mitigate or defer global warming. It has been proposed as a way to slow the atmospheric and marine accumulation of greenhouse gases, which are released by burning fossil fuels.

Carbon dioxide is naturally captured from the atmosphere through biological, chemical or physical processes. Some anthropogenic sequestration techniques exploit these natural processes., while some use entirely artificial processes.

Carbon dioxide may be captured as a pure by-product in processes related to petroleum refining or from flue gases from power generation. CO₂ sequestration includes the storage part of carbon capture and storage, which refers to large-scale, permanent artificial capture and sequestration of industrially produced CO₂ using subsurface saline aquifers, reservoirs, ocean water, aging oil fields, or other carbon sinks.

Sources of carbon offsets

noreply@blogger.com (Gen777) — Sun, 29 May 2011 17:47:00 +0000

The CDM identifies over 200 types of projects suitable for generating carbon offsets, which are grouped into broad categories. These project types include renewable energy, methane abatement, energy efficiency, reforestation and fuel switching.

Renewable energy

Renewable energy offsets commonly include wind power, solar power, hydroelectric power and biofuel. Some of these offsets are used to reduce the cost differential between renewable and conventional energy production, increasing the commercial viability of a choice to use renewable energy sources.

Renewable Energy Credits (RECs) are also sometimes treated as carbon offsets, although the concepts are distinct. Whereas a carbon offset represents a reduction in greenhouse gas emissions, a REC represents a quantity of energy produced from renewable sources. To convert RECs into offsets, the clean energy must be translated into carbon reductions, typically by assuming that the clean energy is displacing an equivalent amount of conventionally produced electricity from the local grid. This is known as an indirect offset (because the reduction doesn't take place at the project site itself, but rather at an external site), and some controversy surrounds the question of whether they truly lead to "additional" emission reductions and who should get credit for any reductions that may occur.

Methane collection and combustion

Some offset projects consist of the combustion or containment of methane generated by farm animals (by use of an anaerobic digester), landfills or other industrial waste. Methane has a global warming potential (GWP) 23 times that of CO₂; when combusted, each molecule of methane is converted to one molecule of CO₂, thus reducing the global warming effect by 96%.

An example of a project using a anaerobic digester can be found in Chile where in December 2000, the largest pork production company in Chile, initiated a voluntary process to implement advanced waste management systems (anaerobic and aerobic digestion of hog manure), in order to reduce greenhouse gas (GHG) emissions.

Energy efficiency

While carbon offsets which fund renewable energy projects help lower the carbon intensity of energy supply, energy conservation projects seek to reduce the overall demand for energy. Carbon offsets in this category fund projects of several types:

Cogeneration plants generate both electricity and heat from the same power source, thus improving upon the energy efficiency of most power plants which waste the energy generated as heat.
Fuel efficiency projects replace a combustion device with one which uses less fuel per unit of energy provided. Assuming energy demand does not change, this reduces the carbon dioxide emitted.
Energy-efficient buildings reduce the amount of energy wasted in buildings through efficient heating, cooling or lighting systems. In particular, the replacement of incandescent light bulbs with compact fluorescent lamps can have a drastic effect on energy consumption. New buildings can also be constructed using less carbon-intensive input materials.

Destruction of industrial pollutants

Industrial pollutants such as hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) have a GWP many thousands of times greater than carbon dioxide by volume. Because these pollutants are easily captured and destroyed at their source, they present a large and low-cost source of carbon offsets. As a category, HFCs, PFCs, and N₂O reductions represent 71% of offsets issued under the CDM.

Land use, land-use change and forestry

Land use, land-use change and forestry (LULUCF) projects focus on natural carbon sinks such as forests and soil. Deforestation, particularly in Brazil, Indonesia and parts of Africa, account for about 20% of greenhouse gas emissions. Deforestation can be avoided either by paying directly for forest preservation, or by using offset funds to provide substitutes for forest-based products. There is a class of mechanisms referred to as REDD schemes (Reducing emissions from deforestation and forest degradation), which may be included in a post-Kyoto agreement. REDD credits provide carbon offsets for the protection of forests, and provide a possible mechanism to allow funding from developed nations to assist in the protection of native forests in developing nations.

Almost half of the world's people burn wood (or fiber or dung) for their cooking and heating needs. Fuel-efficient cook stoves can reduce fuel wood consumption by 30 to 50%, though the warming of the earth due to decreases in particulate matter (i.e. smoke) from such fuel-efficient stoves has not been addressed. There are a number of different types of LULUCF projects:

Avoided deforestation is the protection of existing forests.
Reforestation is the process of restoring forests on land that was once forested.
Afforestation is the process of creating forests on land that was previously unforested, typically for longer than a generation.
Soil management projects attempt to preserve or increase the amount of carbon sequestered in soil.

Purchase of carbon allowances from emissions trading schemes

Voluntary purchasers can offset their carbon emissions by purchasing carbon allowances from legally mandated cap-and-trade programs such as the Regional Greenhouse Gas Initiative or the European Emissions Trading Scheme. By purchasing the allowances that power plants, oil refineries, and industrial facilities need to hold to comply with a cap, voluntary purchases tighten the cap and force additional emissions reductions.

Voluntary purchases can also be made through small-scale and sometimes uncertified schemes such as those offered at South African based Promoting Access to Carbon Equity Centre (PACE), which nevertheless offer clear services such as poverty alleviation in the form of renewable energy development. Also, as "easy carbon credits are coming to an end", these projects have the potential to develop projects that are either too small or too complicated to benefit from legally mandated cap-and-trade programs.

Links with emission trading schemes

Once it has been accredited by the UNFCCC a carbon offset project can be used as carbon credit and linked with official emission trading schemes, such as the European Union Emission Trading Scheme or Kyoto Protocol, as Certified Emission Reductions. European emission allowances for the 2008-2012 second phase were selling for between 21 and 24 Euros per metric ton of CO₂ as of July 2007.

The voluntary Chicago Climate Exchange also includes a carbon offset scheme that allows offset project developers to sell emissions reductions to CCX members who have voluntarily agreed to meet emissions reduction targets.

The Western Climate Initiative, a regional greenhouse gas reduction initiative by states and provinces along the western rim of North America, includes an offset scheme. Likewise, the Regional Greenhouse Gas Initiative, a similar program in the northeastern U.S., includes an offset program. A credit mechanism that uses offsets may be incorporated in proposed schemes such as the Australian Carbon Exchange.

Other

A UK offset provider set up a carbon offsetting scheme which set up a secondary market for treadle pumps in developing countries. These pumps are used by farmers, using human power, in place of diesel pumps. However, given that treadle pumps are best suited to pumping shallow water, while diesel pumps are usually used to pump water from deep boreholes, it is not clear that the treadle pumps are actually achieving real emissions reductions. Other companies have explored and rejected treadle pumps as a viable carbon offsetting approach due to these concerns.

Carbon Retirement

Carbon retirement involves retiring allowances from emission trading schemes as a method for offsetting carbon emissions. Under schemes such as the European Union Emission Trading Scheme, EU Emission Allowances (EUA’s), which represent the right to release carbon dioxide into the atmosphere, are issued to all the largest polluters. The theory is that by buying these allowances and permanently removing them, the price of EUAs increases and provides an incentive for industrial companies to reduce their emissions.

Carbon offset markets

noreply@blogger.com (Gen777) — Sun, 29 May 2011 17:45:00 +0000

Global carbon offset market

In 2009, 8.2 billion metric tons of carbon dioxide equivalent changed hands worldwide, up 68% from 2008, according to the study by carbon-market research firm Point Carbon, of Washington and Oslo. But at EUR94 billion, or about $135 billion, the market's value was nearly unchanged compared with 2008, with world carbon prices averaging EUR11.40 a ton, down about 40% from the previous year, according to the study. The World Bank's "State and Trends of the Carbon Market 2010" put the overall value of the market at $144 billion, but found that a significant part of this figure resulted from manipulation of a VAT loophole.

Carbon offset market in Europe

The global carbon market is dominated by the European Union, where companies that emit greenhouse gases are required to cut their emissions or buy pollution allowances or carbon credits from the market, under the European Union Emission Trading Scheme (EU ETS). Europe, which has seen volatile carbon prices due to fluctuations in energy prices and supply and demand, will continue to dominate the global carbon market for another few years, as the U.S. and China—the world's top polluters—have yet to establish mandatory emission-reduction policies.

Carbon offset market in U.S.

On the whole, the U.S. market remains primarily a voluntary market, but multiple cap and trade regimes are either fully implemented or near-imminent at the regional level. The first mandatory, market-based cap-and-trade program to cut CO₂ in the U.S., called the Regional Greenhouse Gas Initiative (RGGI), kicked into gear in Northeastern states in 2009, growing nearly tenfold to $2.5 billion, according to Point Carbon. Western Climate Initiative (WCI) -- a regional cap-and-trade program including seven western states (California notably among them) and four Canadian provinces—has established a regional target for reducing heat-trapping emissions of 15 percent below 2005 levels by 2020.

Voluntary market

Participants: A wide range of participants are involved in the voluntary market, including providers of different types of offsets, developers of quality assurance mechanisms, third party verifiers, and consumers who purchase offsets from domestic or international providers. Suppliers include for-profit companies, governments, charitable non-governmental organizations, colleges and universities, and other groups.

Motivations: According to industry analyst Ecosystem Marketplace, the voluntary markets present the opportunity for citizen consumer action, as well as an alternative source of carbon finance and an incubator for carbon market innovation. In their survey of voluntary markets, data has shown that “Corporate Social Responsibility” and “Public Relations/Branding” are clearly in first place among motivations for voluntary offset purchases, with evidence indicating that companies seek to offset emissions "for goodwill, both of the general public and their investors."

In addition, regarding market composition, research indicates: "Though many analysts perceive pre-compliance buying as a dominant driving force in the voluntary market, the results of our survey have repeatedly indicated that precompliance motives (as indicated by “investment/resale” and “anticipation of regulation”) remain secondary to those of the pure voluntary market (companies/individuals offsetting their emissions)."

Pre-compliance & trading: The other main category of buyers on the voluntary markets are those engaged in pre-compliance and/or trading. Those purchasing offsets for pre-compliance purposes are doing so with the expectation, or as a hedge against the possibility, of future mandatory cap and trade regulations. As a mandatory cap would sharply increase the price of offsets, firms—especially those with large carbon footprints and the corresponding financial exposure to regulation—make the decision to acquire offsets in advance at what are expected to be lower prices.

The trading market in offsets in general resembles the trade in other commodities markets, with financial professionals including hedge funds and desks at major investment banks, taking positions in the hopes of buying cheap and selling dear, with their motivation typically short or medium term financial gain.

Retail: Multiple players in the retail market have offerings that enable consumers and businesses to calculate their carbon footprint, most commonly through a web-based interface including a calculator or questionnaire, and sell them offsets in the amount of that footprint. In addition many companies selling products and services, especially carbon-intensive ones such as airline travel, offer options to bundle a proportional offsetting amount of carbon credits with each transaction.

Suppliers of voluntary offsets operate under both nonprofit and social enterprise models, or a blended approach sometimes referred to as triple bottom line. Other suppliers include broader environmentally focused organizations with website subsections or initiatives that enable retail voluntary offset purchases by members, and government created projects.

Features of companies that voluntarily offset emissions: Companies which voluntarily offset their own emissions tend to be of relatively low carbon intensity, as they can offset a significant proportion of their emissions at relatively low cost. Voluntary offsetting is particularly common in the financial sector. 61% of financial companies in the FTSE 100 offset at least a portion of their 2009 emissions. 22% of financial companies in the FTSE 100 considered their entire 2009 operations to be carbon neutral.

Carbon Offset

noreply@blogger.com (Gen777) — Sun, 29 May 2011 17:42:00 +0000

A carbon offset is a reduction in emissions of carbon dioxide or greenhouse gases made in order to compensate for or to offset an emission made elsewhere.

Carbon offsets are measured in metric tons of carbon dioxide-equivalent (CO₂e) and may represent six primary categories of greenhouse gases. One carbon offset represents the reduction of one metric ton of carbon dioxide or its equivalent in other greenhouse gases.

There are two markets for carbon offsets. In the larger, compliance market, companies, governments, or other entities buy carbon offsets in order to comply with caps on the total amount of carbon dioxide they are allowed to emit. This market exists in order to achieve compliance with obligations of Annex 1 Parties under the Kyoto Protocol, and of liable entities under the EU Emissions Trading Scheme. In 2006, about $5.5 billion of carbon offsets were purchased in the compliance market, representing about 1.6 billion metric tons of CO₂e reductions.

In the much smaller, voluntary market, individuals, companies, or governments purchase carbon offsets to mitigate their own greenhouse gas emissions from transportation, electricity use, and other sources. For example, an individual might purchase carbon offsets to compensate for the greenhouse gas emissions caused by personal air travel. Many companies offer carbon offsets as an up-sell during the sales process so that customers can mitigate the emissions related with their product or service purchase (such as offsetting emissions related to a vacation flight, car rental, hotel stay, consumer good, etc.). In 2008, about $705 million of carbon offsets were purchased in the voluntary market, representing about 123.4 million metric tons of CO₂e reductions.

Offsets are typically achieved through financial support of projects that reduce the emission of greenhouse gases in the short- or long-term. The most common project type is renewable energy, such as wind farms, biomass energy, or hydroelectric dams. Others include energy efficiency projects, the destruction of industrial pollutants or agricultural byproducts, destruction of landfill methane, and forestry projects. Some of the most popular carbon offset projects from a corporate perspective are energy efficiency and wind turbine projects.

Carbon offsetting has gained some appeal and momentum mainly among consumers in western countries who have become aware and concerned about the potentially negative environmental effects of energy-intensive lifestyles and economies. The Kyoto Protocol has sanctioned offsets as a way for governments and private companies to earn carbon credits which can be traded on a marketplace. The protocol established the Clean Development Mechanism (CDM), which validates and measures projects to ensure they produce authentic benefits and are genuinely "additional" activities that would not otherwise have been undertaken. Organizations that are unable to meet their emissions quota can offset their emissions by buying CDM-approved Certified Emissions Reductions.

Offsets may be cheaper or more convenient alternatives to reducing one's own fossil-fuel consumption. However, some critics object to carbon offsets, and question the benefits of certain types of offsets.

Offsets are viewed as an important policy tool to maintain stable economies. One of the hidden dangers of climate change policy is unequal prices of carbon in the economy, which can cause economic collateral damage if production flows to regions or industries that have a lower price of carbon - unless carbon can be purchased from that area, which offsets effectively permit, equalizing the price.

Definitions of Carbon Offset

The World Resources Institute defines a carbon offset as “a unit of carbon dioxide-equivalent (CO2e) that is reduced, avoided, or sequestered to compensate for emissions occurring elsewhere”.

The Collins English Dictionary defines a carbon offset as “a compensatory measure made by an individual or company for carbon emissions, usually through sponsoring activities or projects which increase carbon dioxide absorption, such as tree planting.”

The Environment Protection Authority of Victoria (Australia) defines a carbon offset as: “a monetary investment in a project or activity elsewhere that abates greenhouse gas (GHG) emissions or sequesters carbon from the atmosphere that is used to compensate for GHG emissions from your own activities. Offsets can be bought by a business or individual in the voluntary market (or within a trading scheme), a carbon offset usually represents one tonne of CO2-e”.

The Stockholm Environment Institute defines a carbon offset as “a credit for negating or diminishing the impact of emitting a ton of carbon dioxide by paying someone else to absorb or avoid the release of a ton of CO2 elsewhere”.

The University of Oxford Environmental Change Institute defines a carbon offset as “mechanism whereby individuals and corporations pay for reductions elsewhere in order to offset their own emissions”.

Features of carbon offsets

Carbon offsets have several common features:

Vintage. The vintage is the year in which the carbon reduction takes place.
Source. The source refers to the project or technology used in offsetting the carbon emissions. Projects can include land-use, methane, biomass, renewable energy and industrial energy efficiency. Projects may also have secondary benefits (co-benefits). For example, projects that reduce agricultural greenhouse gas emissions may improve water quality by reducing fertilizer usage.
Certification regime. The certification regime describes the systems and procedures that are used to certify and register carbon offsets. Different methodologies are used for measuring and verifying emissions reductions, depending on project type, size and location. For example, the Chicago Climate Exchange uses one set of protocols, while the CDM uses another. In the voluntary market, a variety of industry standards exist. These include the Voluntary Carbon Standard and the CDM Gold Standard that are implemented to provide third-party verification of carbon offset projects. There are some additional standards for the validation of co-benefits, including the CCBS, issued by the Climate, Community & Biodiversity Alliance and the Social Carbon Standard, issued by Ecologica Institute.

Carbon Nanofoam

noreply@blogger.com (Gen777) — Sat, 28 May 2011 13:47:00 +0000

Carbon nanofoam is an allotrope of carbon discovered in 1997 by Andrei V. Rode and co-workers at the Australian National University in Canberra. It consists of a low-density cluster-assembly of carbon atoms strung together in a loose three-dimensional web.

Each cluster is about 6 nanometers wide and consists of about 4000 carbon atoms linked in graphite-like sheets that are given negative curvature by the inclusion of heptagons among the regular hexagonal pattern. This is the opposite of what happens in the case of buckminsterfullerenes, in which carbon sheets are given positive curvature by the inclusion of pentagons.

The large-scale structure of carbon nanofoam is similar to that of an aerogel, but with 1% of the density of previously produced carbon aerogels—or only a few times the density of air at sea level. Unlike carbon aerogels, carbon nanofoam is a poor electrical conductor. The nanofoam contains numerous unpaired electrons, which Rode and colleagues propose is due to carbon atoms with only three bonds that are found at topological and bonding defects. This gives rise to what is perhaps carbon nanofoam's most unusual feature: it is attracted to magnets, and below −183 °C can itself be made magnetic.

Estimating Carbon Emissions

noreply@blogger.com (Gen777) — Sat, 28 May 2011 13:44:00 +0000

Emission factors assume a linear relation between the intensity of the activity and the emission resulting from this activity:

Emission_pollutant = Activity * Emission Factor_pollutant

Intensities are also used in projecting possible future scenarios such as those used in the IPCC assessments, along with projected future changes in population, economic activity and energy technologies. The interrelations of these variables is treated under the so-called Kaya identity.

The level of uncertainty of the resulting estimates depends significantly on the source category and the pollutant. Some examples:

Carbon dioxide (CO₂) emissions from the combustion of fuel can be estimated with a high degree of certainty regardless of how the fuel is used as these emissions depend almost exclusively on the carbon content of the fuel, which is generally known with a high degree of precision. The same is true for sulphur dioxide (SO₂), since also sulphur contents of fuels are generally well known. Both carbon and sulphur are almost completey oxidized during combustion and all carbon and sulphur atoms in the fuel will be present in the flue gases as CO₂ and SO₂ respectively.
In contrast, the levels of other air pollutants and non-CO₂ greenhouse gas emissions from combustion depend on the precise technology applied when fuel is combusted. These emissions are basically caused by either incomplete combustion of a small fraction of the fuel (carbon monoxide, methane, non-methane volatile organic compounds) or by complicated chemical and physical processes during the combustion and in the smoke stack or tailpipe. Examples of these are particulates, NO_x, a mixture of nitric oxide, NO, and nitrogen dioxide, NO₂).
Nitrous oxide (N₂O) emissions from agricultural soils are highly uncertain because they depend very much on both the exact conditions of the soil, the application of fertilizers and meteorological conditions.

**Emission factors of common fuels**
Fuel/ Resource	Thermal g(CO₂-eq)/MJ_th	Energy Intensity W·h_th/W·h_e	Electric g(CO₂-eq)/kW·h_e
Coal	B:91.50–91.72 Br:94.33 88	B:2.62–2.85 Br:3.46 3.01	B:863–941 Br:1,175 955
Oil	73	3.40	893
Natural gas	cc:68.20 oc:68.40 51	cc:2.35 oc:3.05	cc:577 oc:751 599
Geothermal Power	3~		T_L0–1 T_H91–122
Uranium Nuclear power		W_L0.18 W_H0.20	W_L60 W_H65
Hydroelectricity		0.046	15
Conc. Solar Pwr			40±15#
Photovoltaics		0.33	106
Wind power		0.066	21

Note: 3.6 MJ = megajoule(s) == 1 kW·h = kilowatt-hour(s), thus 1 g/MJ = 3.6 g/kW·h.
Legend: B = Black coal (supercritical)–(new subcritical), Br = Brown coal (new subcritical), cc = combined cycle, oc = open cycle, T_L = low-temperature/closed-circuit (geothermal doublet), T_H = high-temperature/open-circuit, W_L = Light Water Reactors, W_H = Heavy Water Reactors, #Educated estimate.

Carbon Dioxide With Oceanic Concentration

noreply@blogger.com (Gen777) — Thu, 26 May 2011 17:31:00 +0000

The Earth's oceans contain a huge amount of carbon dioxide in the form of bicarbonate and carbonate ions — much more than the amount in the atmosphere. The bicarbonate is produced in reactions between rock, water, and carbon dioxide. One example is the dissolution of calcium carbonate:

CaCO₃ + CO₂ + H₂O ⇌ Ca²⁺ + 2 HCO−
3

Reactions like this tend to buffer changes in atmospheric CO₂. Since the right-hand side of the reaction produces an acidic compound, adding CO₂ on the left-hand side decreases the pH of sea water, a process which has been termed ocean acidification. Reactions between carbon dioxide and non-carbonate rocks also add bicarbonate to the seas. This can later undergo the reverse of the above reaction to form carbonate rocks, releasing half of the bicarbonate as CO₂. Over hundreds of millions of years this has produced huge quantities of carbonate rocks.

Ultimately, most of the CO₂ emitted by human activities will dissolve in the ocean, however the rate at which the ocean will take it up in the future is less certain.

Carbon Dioxide Past Variation

noreply@blogger.com (Gen777) — Thu, 26 May 2011 17:29:00 +0000

The most direct method for measuring atmospheric carbon dioxide concentrations for periods before direct sampling is to measure bubbles of air (fluid or gas inclusions) trapped in the Antarctic or Greenland ice caps. The most widely accepted of such studies come from a variety of Antarctic cores and indicate that atmospheric CO₂ levels were about 260–280 ppmv immediately before industrial emissions began and did not vary much from this level during the preceding 10,000 years (10 ka). In 1832 Antarctic ice core levels were 284 ppmv.

One study disputed the claim of stable CO₂ levels during the present interglacial of the last 10 ka. Based on an analysis of fossil leaves, Wagner et al. argued that CO₂ levels during the period 7–10 ka were significantly higher (~300 ppm) and contained substantial variations that may be correlated to climate variations. Others have disputed such claims, suggesting they are more likely to reflect calibration problems than actual changes in CO₂. Relevant to this dispute is the observation that Greenland ice cores often report higher and more variable CO₂ values than similar measurements in Antarctica. However, the groups responsible for such measurements (e.g. H. J Smith et al.) believe the variations in Greenland cores result from in situ decomposition of calcium carbonate dust found in the ice. When dust levels in Greenland cores are low, as they nearly always are in Antarctic cores, the researchers report good agreement between Antarctic and Greenland CO₂ measurements.

The longest ice core record comes from East Antarctica, where ice has been sampled to an age of 800 ka. During this time, the atmospheric carbon dioxide concentration has varied by volume between 180–210 ppm during ice ages, increasing to 280–300 ppm during warmer interglacials.

On long timescales, atmospheric CO₂ content is determined by the balance among geochemical processes including organic carbon burial in sediments, silicate rock weathering, and volcanism. The net effect of slight imbalances in the carbon cycle over tens to hundreds of millions of years has been to reduce atmospheric CO₂. The rates of these processes are extremely slow; hence they are of limited relevance to the atmospheric CO₂ response to emissions over the next hundred years.

Various proxy measurements have been used to attempt to determine atmospheric carbon dioxide levels millions of years in the past. These include boron and carbon isotope ratios in certain types of marine sediments, and the number of stomata observed on fossil plant leaves. While these measurements give much less precise estimates of carbon dioxide concentration than ice cores, there is evidence for very high CO₂ volume concentrations between 200 and 150 Ma of over 3,000 ppm and between 600 and 400 Ma of over 6,000 ppm. In more recent times, atmospheric CO₂ concentration continued to fall after about 60 Ma. About 34 Ma, the time of the Eocene-Oligocene extinction event and when the Antarctic ice sheet started to take its current form, CO₂ is found to have been about 760 ppm, and there is geochemical evidence that volume concentrations were less than 300 ppm by about 20 Ma. Low CO₂ concentrations may have been the stimulus that favored the evolution of C4 plants, which increased greatly in abundance between 7 and 5 Ma.

Sources of Carbon Dioxide

noreply@blogger.com (Gen777) — Thu, 26 May 2011 17:27:00 +0000

Natural sources of atmospheric carbon dioxide include volcanic outgassing, the combustion of organic matter, and the respiration processes of living aerobic organisms; man-made sources of carbon dioxide include the burning of fossil fuels for heating, power generation and transport, as well as some industrial processes such as cement making. It is also produced by various microorganisms from fermentation and cellular respiration. Plants convert carbon dioxide to carbohydrates during a process called photosynthesis. They gain the energy needed for this reaction through the absorption of sunlight by pigments such as Chlorophyll. The resulting gas, oxygen, is released into the atmosphere by plants, which is subsequently used for respiration by heterotrophic organisms and other plants, forming a cycle.

Many sources of CO₂ emissions are natural. For example, the natural decay of organic material in forests and grasslands, such as dead trees, results in the release of about 220 gigatonnes of carbon dioxide every year. In 1997, Indonesian peat fires were estimated to have released between 13% and 40% of the average carbon emissions caused by the burning of fossil fuels around the world in a single year. Although the initial carbon dioxide in the atmosphere of the young Earth was produced by volcanic activity, modern volcanic activity releases only 130 to 230 megatonnes of carbon dioxide each year, which is less than 1% of the amount released by human activities.

These natural sources are nearly balanced by natural sinks, physical and biological processes which remove carbon dioxide from the atmosphere. For example, some carbon dioxide dissolves in sea water, and some is directly removed from the atmosphere by land plants for photosynthesis.

There is a large natural flux of CO₂ into and out of the biosphere and oceans. In the pre-industrial era these fluxes were largely in balance. Currently about 57% of human-emitted CO₂ is removed by the biosphere and oceans. The ratio of the increase in atmospheric CO₂ to emitted CO₂ is known as the airborne fraction (Keeling et al., 1995); this varies for short-term averages but is typically about 45% over longer (5 year) periods.

Burning fossil fuels such as coal and petroleum is the leading cause of increased anthropogenic CO₂; deforestation is the second major cause. In 2008, 8.67 gigatonnes of carbon (31.8 gigatonnes of CO₂) were released from fossil fuels worldwide, compared to 6.14 gigatonnes in 1990. In addition, land use change contributed 1.20 gigatonnes in 2008, compared to 1.64 gigatonnes in 1990.

This addition, about 3% of annual natural emissions as of 1997, is sufficient to exceed the balancing effect of sinks. As a result, carbon dioxide has gradually accumulated in the atmosphere, and as of 2009, its concentration is 39% above pre-industrial levels.

Various techniques have been proposed for removing excess carbon dioxide from the atmosphere in carbon dioxide sinks.

Carbon Dioxide Management

noreply@blogger.com (Gen777) — Thu, 26 May 2011 17:20:00 +0000

Carbon dioxide concentrations are growing rapidly and accelerating. The observed concentration rise is through multiple lines of evidence directly attributable to the use of gas, oil and coal. Of any emitted carbon dioxide, about 40% remains semi-permanent in the atmosphere. According to a 2007 report by the Intergovernmental Panel on Climate Change, "About 50% of a CO₂ increase will be removed from the atmosphere within 30 years, and a further 30% will be removed within a few centuries. The remaining 20% may stay in the atmosphere for many thousands of years."

Three longer term processes are recognized to redistribute and eventually dissipate currently emitted carbon dioxide. The first will be ocean invasion (300 years), which can only reduce concentration by a factor of ~4, because of the establishment of a new equilibrium. The second will be a new equilibrium with carbon carbonate, which can reduce the concentration by a factor of ~3 over a 5,000 year timescale. The third stage is eventual reaction with igneous rock with a time-constant of 400,000 years. These processes are so slow, that practically zero-emissions are at some point unavoidable in order to not exceed any practical carbon dioxide concentration limit.

To avoid a global warming of 2.1°C, it is estimated that a concentration of less than 450 ppm needs to be maintained if other gasses were to return to pre-industrial levels. Currently a global warming of 0.7°C is measured, with another 0.6°C increase expected even without any further increased concentrations because the oceans are still being warmed along with the atmosphere. At the current accelerated growth rate, exponentially extrapolating the Keeling curve, this concentration will be reached in 22 years. Even with constant concentration growth, with the current 2.2 ppm/yr, this concentration will be reached in (450-390 ppm)/(2.2 ppm/yr)=27 years. These timescales are so short with respect to the timescale of the evolution such there is little doubt these concentrations will be reached soon barring any drastic behavior changes. Indeed, the lifetime of for instance power plants can be 40 to 60 years. To avoid these concentrations, an immediate reduction of the concentration growth of 3.5% per year rather than a growth of the concentration growth of 1.7% per year needs to be achieved for the foreseeable future. Reducing the concentration growth can be done by restricting emissions or with carbon sequestration. The concentration growth is dominantly affected by the net human emissions.

The current increase to 386 ppm from 280 ppm causes a radiative forcing of 1.66 W/m^2, and 1.34 W/m^2 from increases in other gases, totaling 3.00 W/m^2. The current concentration of greenhouse gases already have a heating power equaling that of a concentration of (386−280)×3.00/1.66 + 280 = 472 ppm C02-eq (carbon dioxide equivalent). Therefore, the current concentrations are high enough for over a 2 degrees Celsius temperature rise.

To be able to reduce carbon dioxide concentration with Carbon sequestration back to pre-industrial levels, (390−280 ppm)/390ppm/(50%/100) = 70% of all the existing air needs to be scrubbed off any carbon dioxide, where 50% is the percentage of carbon dioxide residing in the atmosphere (and not in the oceans), removing about (390−280 ppm)/(50%/100) = 0.03% of the air, an immense task.

Carbon Flux

noreply@blogger.com (Gen777) — Thu, 26 May 2011 17:17:00 +0000

Carbon Flux or Carbon dioxide in Earth's atmosphere is concentration of carbon dioxide (CO₂) in Earth's atmosphere is approximately 390 ppm (parts per million) by volume as of 2010and rose by 1.9 ppm/yr during 2000–2009. Carbon dioxide is essential to photosynthesis in plants and other photoautotrophs, and is also a prominent greenhouse gas. Despite its relatively small overall concentration in the atmosphere, CO₂ is an important component of Earth's atmosphere because it absorbs and emits infrared radiation at wavelengths of 4.26 µm (asymmetric stretching vibrational mode) and 14.99 µm (bending vibrational mode), thereby playing a role in the greenhouse effect. The present level is higher than at any time during the last 800 thousand years, and likely higher than in the past 20 million years.

In 2009, the CO₂ global average concentration in Earth's atmosphere was about 0.0387% by volume, or 387 parts per million by volume (ppmv). There is an annual fluctuation of about 3–9 ppmv which roughly follows the Northern Hemisphere's growing season. The Northern Hemisphere dominates the annual cycle of CO₂ concentration because it has much greater land area and plant biomass than the Southern Hemisphere. Concentrations peak in May as the Northern Hemisphere spring greenup begins and reach a minimum in October when the quantity of biomass undergoing photosynthesis is greatest.

Carbon dioxide has unique long-term effects on climate change that are largely "irreversible" for one thousand years after emissions stop (zero further emissions). The greenhouse gases methane and nitrous oxide do not persist over time in the same way as carbon dioxide. Even if carbon emissions were to completely cease, atmospheric temperatures are not expected to decrease significantly.

Carbon Fixation

noreply@blogger.com (Gen777) — Thu, 26 May 2011 17:14:00 +0000

Carbon fixation refers to any process through which gaseous carbon dioxide is converted into a solid compound. It refers mostly to the processes found in autotrophs (organisms that produce their own food), usually driven by photosynthesis, whereby carbon dioxide is changed into sugars. Carbon fixation can also be carried out by the process of calcification in marine calcifying organisms such as Emiliania huxleyi and also by heterotrophic organisms in some circumstances.

Plants

The Calvin cycle is the most common biological method of carbon fixation.

In plants, there are three types of carbon fixation during photosynthesis:

C₃ plants that use the Calvin cycle for the initial steps that incorporate CO₂ into organic matter, forming a 3-carbon compound as the first stable. This form of photosynthesis occurs in the majority of terrestrial species of plants. Plants that use this pathway have a carbon isotope signature of -24 to -33‰.
C₄ plants that preface the Calvin cycle with reactions that incorporate CO₂ into a 4-carbon compound. C4 plants have a distinctive internal leaf anatomy. Tropical grasses, such as sugar cane and maize are C4 plants, but there are many broadleaf plants that are C4. Overall, 7600 species of terrestrial plants use C₄ carbon fixation, representing around 3% of all species. These plants have a carbon isotope signature of -16 to -10 ‰.
CAM-plants that use Crassulacean acid metabolism as an adaptation for arid conditions. CO₂ enters through the stomata during the night and is converted into organic acids, which release CO₂ for use in the Calvin cycle during the day, when the stomata are closed. The jade plant (Crassula ovata) and cacti are typical of CAM plants. Sixteen thousand species of plants use CAM.These plants have a carbon isotope signature of -20 to -10 ‰.

Microorganisms

In addition to the Calvin cycle, the following alternative pathways are currently known to be used in certain autotrophic microorganisms:

Reverse Krebs cycle (also known as the reverse tricarboxylic acid cycle, the reverse TCA cycle, or the reverse citric acid cycle). The reaction is the Citric acid cycle run in reverse and is used by photolitho-autotrophic bacteria of the Chlorobiales and some chemolitho-autotrophic sulfate-reducing bacteria.
Reductive acetyl CoA Pathway is found in methanogenic archaea and in acetogenic and some sulfate-reducing bacteria as a way of fixing carbon.
3-Hydroxypropionate Pathway is found in photolitho-autotrophically grown bacteria of the genus Chloroflexus and, in modified form, in some chemolitho-autotrophically grown archaea as a way of fixing carbon.

Heterotrophs

Although almost all heterotrophs cannot synthesize complete organic molecules from carbon dioxide, some carbon dioxide is incorporated in their metabolism. Notably pyruvate carboxylase consumes carbon dioxide (as carbonate ions) as part of gluconeogenesis.

Carbon Emissions Trading Systems

noreply@blogger.com (Gen777) — Wed, 25 May 2011 13:22:00 +0000

As the IPCC reports came in over the years they shed abundant light on the true state of global warming and they gave support to the environmental effort to address this unprecedented problem. However, the same discussions that started decades back had never ceased and the crusade for a tangible solution to global climate change had gone on all the while. In 1997 the Kyoto Protocol was adopted. The Kyoto Protocol is a 1997 international treaty which came into force in 2005. In the treaty, most developed nations agreed to legally binding targets for their emissions of the six major greenhouse gases. Emission quotas (known as "Assigned amounts") were agreed by each participating 'Annex 1' country, with the intention of reducing the overall emissions by 5.2% from their 1990 levels by the end of 2012. The United States is the only industrialized nation under Annex I that has not ratified the treaty, and is therefore not bound by it. The Intergovernmental Panel on Climate Change has projected that the financial effect of compliance through trading within the Kyoto commitment period will be limited at between 0.1-1.1% of GDP among trading countries.

The Protocol defines several mechanisms ("flexible mechanisms") that are designed to allow Annex I countries to meet their emission reduction commitments (caps) with reduced economic impact (IPCC, 2007).

Under Article 3.3 of the Kyoto Protocol, Annex 1 Parties may use GHG removals, from afforestation and reforestation (forest sinks) and deforestation (sources) since 1990, to meet their emission reduction commitments.

Annex 1 Parties may also use International Emissions Trading (IET). Under the treaty, for the 5-year compliance period from 2008 until 2012, nations that emit less than their quota will be able to sell Assigned amount units to nations that exceed their quota. It is also possible for Annex I countries to sponsor carbon projects that reduce greenhouse gas emissions in other countries. These projects generate tradable carbon credits that can be used by Annex I countries in meeting their caps. The project-based Kyoto Mechanisms are the Clean Development Mechanism (CDM) and Joint Implementation (JI).

The CDM covers projects taking place in non-Annex I countries, while JI covers projects taking place in Annex I countries. CDM projects are supposed to contribute to sustainable development in developing countries, and also generate "real" and "additional" emission savings, i.e., savings that only occur thanks to the CDM project in question (Carbon Trust, 2009, p. 14). Whether or not these emission savings are genuine is, however, difficult to prove (World Bank, 2010, pp. 265–267).

Australia

Garnaut Draft Report

In 2003 the New South Wales (NSW) state government unilaterally established the NSW Greenhouse Gas Abatement Scheme to reduce emissions by requiring electricity generators and large consumers to purchase NSW Greenhouse Abatement Certificates (NGACs). This has prompted the rollout of free energy-efficient compact fluorescent lightbulbs and other energy-efficiency measures, funded by the credits. This scheme has been criticised by the Centre for Energy and Environmental Markets (CEEM) of the UNSW because of its lack of effectiveness in reducing emissions, its lack of transparency and its lack of verification of the additionality of emission reductions.

On 4 June 2007, former Prime Minister John Howard announced an Australian Carbon Trading Scheme to be introduced by 2012, but opposition parties called the plan "too little, too late". On 24 November 2007 Howard's coalition government lost a general election and was succeeded by the Labor Party, with Kevin Rudd taking over as prime minister. Prime Minister Rudd announced that a cap-and-trade emissions trading scheme would be introduced in 2010, however this scheme was initially delayed by a year to mid-2011, and in May 2010, it was subsequently delayed further until 2013.

Australia's Commonwealth, State and Territory Governments commissioned the Garnaut Climate Change Review, a study by Professor Ross Garnaut on the mechanism of a potential emissions trading scheme. Its interim report was released on 21 February 2008. It recommended an emissions trading scheme that includes transportation but not agriculture, and that emissions permits should be sold competitively and not allocated free to carbon polluters. It recognised that energy prices will increase and that low income families will need to be compensated. It recommended more support for research into low emissions technologies and a new body to oversee such research. It also recognised the need for transition assistance for coal mining areas.

In response to Garnaut's draft report, the Rudd Labor government issued a Green Paper on 16 July that described the intended design of the actual trading scheme.

Subsequent to this, the emission trading scheme proposed by the Government was defeated in the Senate, with the Opposition, the Greens and two independent senators opposing the proposed legislation.

New Zealand

The New Zealand Emissions Trading Scheme (NZ ETS) is a national all-sectors all-greenhouse gases uncapped emissions trading scheme first legislated in September 2008 by the Fifth Labour Government of New Zealand and amended in November 2009 by the Fifth National Government of New Zealand.

Although the NZ ETS covers all-sectors and all-gases, individual sectors of the economy have different entry dates when their obligations to report emissions and surrender emission units have effect. Forestry, a net sink which contributed removals of 14 Mts of CO₂e in 2008 or 19% of NZ's 2008 emissions, entered on 1 January 2008. Emissions from stationary energy, industrial and liquid fossil fuel sectors (34 Mts in 2008, 45% of 2008 emissions, entered the NZ ETS on 1 July 2010. Agricultural emissions (mainly 35 Mts of methane and nitrous oxide emissions from pastoral ruminants or 47% of 2008 emissions) do not enter the scheme until 1 January 2015.

Tradable emission units will be issued by free allocation to emitters, with no auctions in the short term. The fishing sector will receive free units on a historic basis, 90 per cent of their 2005 emissions (bullet points 9 & 10 MfE September 2009). Pre-1990 forests will receive a fixed free allocation of 60 emissions units per hectare. Allocation to emissions-intensive industry, and agriculture will be provided on an output-intensity basis, which will be based on the industry average emissions per unit of output and will be uncapped. Bertram and Terry (2010, p 16 ) state that as there is no 'cap' on emissions, the NZ ETS is not a cap and trade scheme as understood in the economics literature.

A transition period will operate from 1 July 2010 until 31 December 2012. During this period the price of New Zealand Emissions Units (NZUs) will be capped at NZ$25. Also, one unit will only need to be surrendered for every two tonnes of carbon dioxide equivalent emissions, effectively reducing the carbon price to NZ$12.50 per tonne (MfE 2009, second bullet point).

Section 3 of the Climate Change Response Act 2002 (the Act) defines the purpose of the Act as to reduce emissions from business-as-usual-levels and to fulfill New Zealand's international obligations under the United Nations Frame Work Convention on Climate Change (UNFCCC) and the Kyoto Protocol. Some stakeholders have criticized the New Zealand Emissions Trading Scheme for its generous free allocations of emission units and the lack of a carbon price signal (the Parliamentary Commissioner for the Environment), and being ineffective in reducing emissions (Greenpeace NZ).

European Union

The European Union Emission Trading Scheme (or EU ETS) is the largest multi-national, greenhouse gas emissions trading scheme in the world. It is one of the EU's central policy instruments to meet their cap set in the Kyoto Protocol (Jones et al.., 2007, p. 64).

After voluntary trials in the UK and Denmark, Phase I commenced operation in January 2005 with all 15 (now 25 of the 27) member states of the European Union participating. The program caps the amount of carbon dioxide that can be emitted from large installations with a net heat supply in excess of 20 MW, such as power plants and carbon intensive factories and covers almost half (46%) of the EU's Carbon Dioxide emissions. Phase I permits participants to trade amongst themselves and in validated credits from the developing world through Kyoto's Clean Development Mechanism.

During Phases I and II, allowances for emissions have typically been given free to firms, which has resulted in them getting windfall profits (CCC, 2008, p. 149). Ellerman and Buchner (2008) (referenced by Grubb et al.., 2009, p. 11) suggested that during its first two years in operation, the EU ETS turned an expected increase in emissions of 1-2 percent per year into a small absolute decline. Grubb et al.. (2009, p. 11) suggested that a reasonable estimate for the emissions cut achieved during its first two years of operation was 50-100 MtCO₂ per year, or 2.5-5 percent.

A number of design flaws have limited the effectiveness of scheme (Jones et al.., 2007, p. 64). In the initial 2005-07 period, emission caps were not tight enough to drive a significant reduction in emissions (CCC, 2008, p. 149). The total allocation of allowances turned out to exceed actual emissions. This drove the carbon price down to zero in 2007. This oversupply reflects the difficulty in predicting future emissions which is necessary in setting a cap.

Phase II saw some tightening, but the use of JI and CDM offsets was allowed, with the result that no reductions in the EU will be required to meet the Phase II cap (CCC, 2008, pp. 145, 149). For Phase II, the cap is expected to result in an emissions reduction in 2010 of about 2.4% compared to expected emissions without the cap (business-as-usual emissions) (Jones et al.., 2007, p. 64). For Phase III (2013–20), the European Commission has proposed a number of changes, including:

the setting an overall EU cap, with allowances then allocated to EU members;
tighter limits on the use of offsets;
unlimiting banking of allowances between Phases II and III;
and a move from allowances to auctioning.

In January 2008 Norway, Iceland, and Lichtenstein, joined the European Union Emissions Trading System (EU ETS) according to a publication from the European Commission. The Norwegian Ministry of the Environment has also released its draft National Allocation Plan which provides a carbon cap-and-trade of 15 million metric tonnes of CO₂, 8 million of which are set to be auctioned. According to the OECD Economic Survey of Norway 2010, the nation "has announced a target for 2008-12 10% below its commitment under the Kyoto Protocol and a 30% cut compared with 1990 by 2020."

Tokyo, Japan

The Japanese city of Tokyo is like a country in its own right in terms of its energy consumption and GDP. Tokyo consumes as much energy as "entire countries in Northern Europe, and its production matches the GNP of the world’s 16th largest country". Originally, Japan had its own cap and trade system that had been in place for some years, but was not effective. Japan has its own emission reduction policy but not a nationwide cap and trade program. This climate strategy is enforced and overseen by the Tokyo Metropolitan Government (TMG). The first phase, which is alike to Japan's scheme, runs up to 2014, these organizations will have to cut their carbon emissions by 6%; those who fail to operate within their emission caps will from 2011 on be required to purchase emission allowances to cover any excess emissions, or alternatively, invest in renewable energy certificates or offset credits issued by smaller businesses or branch offices. Firms whom fail to comply will face fines. According to local reports, organizations that do not operate within their caps will also be ordered to cut emissions by 1.3 times the amount they failed to reduce during the first phase of the scheme. The long term aim is to cut the metropolis' carbon emissions by 25% from 2000 levels by 2020.

United States

An early example of an emission trading system has been the SO₂ trading system under the framework of the Acid Rain Program of the 1990 Clean Air Act in the U.S. Under the program, which is essentially a cap-and-trade emissions trading system, SO₂ emissions were reduced by 50% from 1980 levels by 2007. Some experts argue that the cap-and-trade system of SO₂ emissions reduction has reduced the cost of controlling acid rain by as much as 80% versus source-by-source reduction.

In 1997, the State of Illinois adopted a trading program for volatile organic compounds in most of the Chicago area, called the Emissions Reduction Market System. Beginning in 2000, over 100 major sources of pollution in eight Illinois counties began trading pollution credits.

In 2003, New York State proposed and attained commitments from nine Northeast states to form a cap-and-trade carbon dioxide emissions program for power generators, called the Regional Greenhouse Gas Initiative (RGGI). This program launched on January 1, 2009 with the aim to reduce the carbon "budget" of each state's electricity generation sector to 10% below their 2009 allowances by 2018.

Also in 2003, U.S. corporations were able to trade CO₂ emission allowances on the Chicago Climate Exchange under a voluntary scheme. In August 2007, the Exchange announced a mechanism to create emission offsets for projects within the United States that cleanly destroy ozone-depleting substances.

Also in 2003, the Environmental Protection Agency (EPA) began to administer the NOx Budget Trading Program (NBP)under the NOx State Implementation Plan (also known as the “NOx SIP Call”) The NOx Budget Trading Program was a market-based cap and trade program created to reduce emissions of nitrogen oxides (NOx) from power plants and other large combustion sources in the eastern United States. NOx is a prime ingredient in the formation of ground-level ozone (smog), a pervasive air pollution problem in many areas of the eastern United States. The NBP was designed to reduce NOx emissions during the warm summer months, referred to as the ozone season, when ground-level ozone concentrations are highest. In March 2008, EPA again strengthened the 8-hour ozone standard to 0.075 parts per million (ppm) from its previous 0.008 ppm.

In 2006, the California Legislature passed the California Global Warming Solutions Act, AB-32, which was signed into law by Governor Arnold Schwarzenegger. Thus far, flexible mechanisms in the form of project based offsets have been suggested for five main project types. The project types include: manure management, forestry, building energy, SF₆, and landfill gas capture. However, a recent ruling from Judge Ernest H. Goldsmith of San Francisco's Superior Court states that the rules governing California's cap-and-trade system were adopted without a proper analysis of alternative methods to reduce greenhouse gas emissions. The tentative ruling, issued on January 24, 2011, argues that the California Air Resources Board violated state environmental law by failing to consider such alternatives. If the decision is made final, the state would not be allowed to implement its proposed cap-and-trade system until the California Air Resources Board fully complies with the California Environmental Quality Act.

Since February 2007, seven U.S. states and four Canadian provinces have joined together to create the Western Climate Initiative (WCI),a regional greenhouse gas emissions trading system. July 2010, a meeting took place to further outline the cap-and-trade system which if accepted would curb greenhouse gas emissions by January 2012.

On November 17, 2008 President-elect Barack Obama clarified, in a talk recorded for YouTube, his intentions for the US to enter a cap-and-trade system to limit global warming.

The 2010 United States federal budget proposes to support clean energy development with a 10-year investment of US $15 billion per year, generated from the sale of greenhouse gas (GHG) emissions credits. Under the proposed cap-and-trade program, all GHG emissions credits would be auctioned off, generating an estimated $78.7 billion in additional revenue in FY 2012, steadily increasing to $83 billion by FY 2019.^[100]

The American Clean Energy and Security Act (H.R. 2454) , a greenhouse gas cap-and-trade bill, was passed on June 26, 2009, in the House of Representatives by a vote of 219-212. The bill originated in the House Energy and Commerce Committee and was introduced by Rep. Henry A. Waxman and Rep. Edward J. Markey. It was never passed in the Senate. The big Republican wins in the November 2010 U.S. Congressional election have further reduced the chances of a climate bill being adopted during President Barack Obama's first term.

Renewable energy certificates

Renewable Energy Certificates, or "green tags", are transferable rights for renewable energy within some American states. A renewable energy provider gets issued one green tag for each 1,000 kWh of energy it produces. The energy is sold into the electrical grid, and the certificates can be sold on the open market for profit. They are purchased by firms or individuals in order to identify a portion of their energy with renewable sources and are voluntary.

They are typically used like an offsetting scheme or to show corporate responsibility, although their issuance is unregulated, with no national registry to ensure there is no double-counting. However, it is one way that an organization could purchase its energy from a local provider who uses fossil fuels, but back it with a certificate that supports a specific wind or hydro power project.

Carbon Emissions Trading

noreply@blogger.com (Gen777) — Wed, 25 May 2011 13:20:00 +0000

Carbon Emissions trading is a market-based approach used to control pollution by providing economic incentives for achieving reductions in the emissions of pollutants.^[1] It is a form of carbon pricing.

A central authority (usually a governmental body) sets a limit or cap on the amount of a pollutant that can be emitted. The limit or cap is allocated or sold to firms in the form of emissions permits which represent the right to emit or discharge a specific volume of the specified pollutant. Firms are required to hold a number of permits (or carbon credits) equivalent to their emissions. The total number of permits cannot exceed the cap, limiting total emissions to that level. Firms that need to increase their emission permits must buy permits from those who require fewer permits. The transfer of permits is referred to as a trade. In effect, the buyer is paying a charge for polluting, while the seller is being rewarded for having reduced emissions. Thus, in theory, those who can reduce emissions most cheaply will do so, achieving the pollution reduction at the lowest cost to society.

There are active trading programs in several air pollutants. For greenhouse gases the largest is the European Union Emission Trading Scheme. In the United States there is a national market to reduce acid rain and several regional markets in nitrogen oxides. Markets for other pollutants tend to be smaller and more localized.

The overall goal of an emissions trading plan is to minimize the cost of meeting a set emissions target. The cap is an enforceable limit on emissions that is usually lowered over time — aiming towards a national emissions reduction target. In other systems a portion of all traded credits must be retired, causing a net reduction in emissions each time a trade occurs. In many cap-and-trade systems, organizations which do not pollute may also participate, thus environmental groups can purchase and retire allowances or credits and hence drive up the price of the remainder according to the law of demand. Corporations can also prematurely retire allowances by donating them to a nonprofit entity and then be eligible for a tax deduction.

By definition, an externality is an activity of one entity that affects the welfare of another entity in a way that is outside the market mechanism. Pollution is the prime example most economists think of when discussing externalities. There are many different ways to address these from a public economics perspective including emissions fees, cap-and-trade, and command-and-control regulation. Here we will discuss cap-and-trade as the chosen public response to externalities.

The economics literature provides the following definitions of cap and trade emissions trading schemes.

A cap-and-trade system constrains the aggregate emissions of regulated sources by creating a limited number of tradable emission allowances, which emission sources must secure and surrender in number equal to their emissions.

In an emissions trading or cap-and-trade scheme, a limit on access to a resource (the cap) is defined and then allocated among users in the form of permits. Compliance is established by comparing actual emissions with permits surrendered including any permits traded within the cap.

Under a tradable permit system, an allowable overall level of pollution is established and allocated among firms in the form of permits. Firms that keep their emission levels below their allotted level may sell their surplus permits to other firms or use them to offset excess emissions in other parts of their facilities.

Artificial sequestration - Carbon Dioxide Sink

noreply@blogger.com (Gen777) — Tue, 24 May 2011 16:17:00 +0000

For carbon to be sequestered artificially (i.e. not using the natural processes of the carbon cycle) it must first be captured, or it must be significantly delayed or prevented from being re-released into the atmosphere (by combustion, decay, etc.) from an existing carbon-rich material, by being incorporated into an enduring usage (such as in construction). Thereafter it can be passively stored or remain productively utilized over time in a variety of ways.

For example, upon harvesting, wood (as a carbon-rich material) can be immediately burned or otherwise serve as a fuel, returning its carbon to the atmosphere, or it can be incorporated into construction or a range of other durable products, thus sequestering its carbon over years or even centuries. One ton of dry wood is equivalent to 1.8 tons of carbon dioxide.

Indeed, a very carefully designed and durable, energy-efficient and energy-capturing building has the potential to sequester (in its carbon-rich construction materials), as much as or more carbon than was released by the acquisition and incorporation of all its materials and than will be released by building-function "energy-imports" during the structure's (potentially multi-century) existence. Such a structure might be termed "carbon neutral" or even "carbon negative". Building construction and operation (electricity usage, heating, etc.) are estimated to contribute nearly half of the annual human-caused carbon additions to the atmosphere.

Natural-gas purification plants often already have to remove carbon dioxide, either to avoid dry ice clogging gas tankers or to prevent carbon-dioxide concentrations exceeding the 3% maximum permitted on the natural-gas distribution grid.

Beyond this, one of the most likely early applications of carbon capture is the capture of carbon dioxide from flue gases at power stations (in the case of coal, this is known as "clean coal"). A typical new 1000 MW coal-fired power station produces around 6 million tons of carbon dioxide annually. Adding carbon capture to existing plants can add significantly to the costs of energy production; scrubbing costs aside, a 1000 MW coal plant will require the storage of about 50 million barrels of carbon dioxide a year. However, scrubbing is relatively affordable when added to new plants based on coal gasification technology, where it is estimated to raise energy costs for households in the United States using only coal-fired electricity sources from 10 cents per kW·h to 12 cents.

Carbon capture

Currently, capture of carbon dioxide is performed on a large scale by absorption of carbon dioxide onto various amine-based solvents. Other techniques are currently being investigated, such as pressure swing adsorption, temperature swing adsorption, gas separation membranes, and cryogenics. Recent pilot studies include flue capture and conversion to baking soda and use of algae for conversion to fuel or feed.

In coal-fired power stations, the main alternatives to retrofitting amine-based absorbers to existing power stations are two new technologies: coal gasification combined-cycle and oxy-fuel combustion. Gasification first produces a "syngas" primarily of hydrogen and carbon monoxide, which is burned, with carbon dioxide filtered from the flue gas. Oxy-fuel combustion burns the coal in oxygen instead of air, producing only carbon dioxide and water vapour, which are relatively easily separated. Some of the combustion products must be returned to the combustion chamber, either before or after separation, otherwise the temperatures would be too high for the turbine.

Another long-term option is carbon capture directly from the air using hydroxides. The air would literally be scrubbed of its CO₂ content. This idea offers an alternative to non-carbon-based fuels for the transportation sector.

Examples of carbon sequestration at coal plants include converting carbon from smokestacks into baking soda, and algae-based carbon capture, circumventing storage by converting algae into fuel or feed.

Oceans

Another proposed form of carbon sequestration in the ocean is direct injection. In this method, carbon dioxide is pumped directly into the water at depth, and expected to form "lakes" of liquid CO₂ at the bottom. Experiments carried out in moderate to deep waters (350–3600 m) indicate that the liquid CO₂ reacts to form solid CO₂ clathrate hydrates, which gradually dissolve in the surrounding waters.

This method, too, has potentially dangerous environmental consequences. The carbon dioxide does react with the water to form carbonic acid, H₂CO₃; however, most (as much as 99%) remains as dissolved molecular CO₂. The equilibrium would no doubt be quite different under the high pressure conditions in the deep ocean. In addition, if deep-sea bacterial methanogens that reduce carbon dioxide were to encounter the carbon dioxide sinks, levels of methane gas may increase, leading to the generation of an even worse greenhouse gas. The resulting environmental effects on benthic life forms of the bathypelagic, abyssopelagic and hadopelagic zones are unknown. Even though life appears to be rather sparse in the deep ocean basins, energy and chemical effects in these deep basins could have far-reaching implications. Much more work is needed here to define the extent of the potential problems.

Carbon storage in or under oceans may not be compatible with the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter.

An additional method of long-term ocean-based sequestration is to gather crop residue such as corn stalks or excess hay into large weighted bales of biomass and deposit it in the alluvial fan areas of the deep ocean basin. Dropping these residues in alluvial fans would cause the residues to be quickly buried in silt on the sea floor, sequestering the biomass for very long time spans. Alluvial fans exist in all of the world's oceans and seas where river deltas fall off the edge of the continental shelf such as the Mississippi alluvial fan in the gulf of Mexico and the Nile alluvial fan in the Mediterranean Sea. A downside, however, would be an increase in aerobic bacteria growth due to the introduction of biomass, leading to more competition for oxygen resources in the deep sea, similar to the oxygen minimum zone.

Geological sequestration

The method of geo-sequestration or geological storage involves injecting carbon dioxide directly into underground geological formations. Declining oil fields, saline aquifers, and unminable coal seams have been suggested as storage sites. Caverns and old mines that are commonly used to store natural gas are not considered, because of a lack of storage safety.

CO₂ has been injected into declining oil fields for more than 40 years, to increase oil recovery. This option is attractive because the storage costs are offset by the sale of additional oil that is recovered. Typically, 10-15% additional recovery of the original oil in place is possible. Further benefits are the existing infrastructure and the geophysical and geological information about the oil field that is available from the oil exploration. Another benefit of injecting CO₂ into Oil fields is that CO₂ is soluble in oil. Dissolving CO₂ in oil lowers the viscosity of the oil and reduces its interfacial tension which increases the oils mobility. All oil fields have a geological barrier preventing upward migration of oil. As most oil and gas has been in place for millions to tens of millions of years, depleted oil and gas reservoirs can contain carbon dioxide for millennia. Identified possible problems are the many 'leak' opportunities provided by old oil wells, the need for high injection pressures and acidification which can damage the geological barrier. Other disadvantages of old oil fields are their limited geographic distribution and depths, which require high injection pressures for sequestration. Below a depth of about 1000 m, carbon dioxide is injected as a supercritical fluid, a material with the density of a liquid, but the viscosity and diffusivity of a gas. Unminable coal seams can be used to store CO₂, because CO₂ absorbs to the coal surface, ensuring safe long-term storage. In the process it releases methane that was previously adsorbed to the coal surface and that may be recovered. Again the sale of the methane can be used to offset the cost of the CO₂ storage. Release or burning of methane would of course at least partially offset the obtained sequestration result – except when the gas is allowed to escape into the atmosphere in significant quantities: methane has a higher global warming potential than CO₂.

Saline aquifers contain highly mineralized brines and have so far been considered of no benefit to humans except in a few cases where they have been used for the storage of chemical waste. Their advantages include a large potential storage volume and relatively common occurrence reducing the distance over which CO₂ has to be transported. The major disadvantage of saline aquifers is that relatively little is known about them compared to oil fields. Another disadvantage of saline aquifers is that as the salinity of the water increases, less CO₂ can be dissolved into aqueous solution. To keep the cost of storage acceptable the geophysical exploration may be limited, resulting in larger uncertainty about the structure of a given aquifer. Unlike storage in oil fields or coal beds, no side product will offset the storage cost. Leakage of CO₂ back into the atmosphere may be a problem in saline-aquifer storage. However, current research shows that several trapping mechanisms immobilize the CO₂ underground, reducing the risk of leakage.

A major research project examining the geological sequestration of carbon dioxide is currently being performed at an oil field at Weyburn in south-eastern Saskatchewan. In the North Sea, Norway's Statoil natural-gas platform Sleipner strips carbon dioxide out of the natural gas with amine solvents and disposes of this carbon dioxide by geological sequestration. Sleipner reduces emissions of carbon dioxide by approximately one million tonnes a year. The cost of geological sequestration is minor relative to the overall running costs. As of April 2005, BP is considering a trial of large-scale sequestration of carbon dioxide stripped from power plant emissions in the Miller oilfield as its reserves are depleted.

In October 2007, the Bureau of Economic Geology at The University of Texas at Austin received a 10-year, $38 million subcontract to conduct the first intensively monitored, long-term project in the United States studying the feasibility of injecting a large volume of CO₂ for underground storage. The project is a research program of the Southeast Regional Carbon Sequestration Partnership (SECARB), funded by the National Energy Technology Laboratory of the U.S. Department of Energy (DOE). The SECARB partnership will demonstrate CO₂ injection rate and storage capacity in the Tuscaloosa-Woodbine geologic system that stretches from Texas to Florida. Beginning in fall 2007, the project will inject CO₂ at the rate of one million tons per year, for up to 1.5 years, into brine up to 10,000 feet (3,000 m) below the land surface near the Cranfield oil field about 15 miles (24 km) east of Natchez, Mississippi. Experimental equipment will measure the ability of the subsurface to accept and retain CO₂.

Mineral sequestration

Mineral sequestration aims to trap carbon in the form of solid carbonate salts. This process occurs slowly in nature and is responsible for the deposition and accumulation of limestone (calcium carbonate) over geologic time. Carbonic acid in groundwater slowly reacts with complex silicates to dissolve calcium, magnesium, alkalis and silica and leave a residue of clay minerals. The dissolved calcium and magnesium react with bicarbonate to precipitate calcium and magnesium carbonates, a process that organisms use to make shells. When the organisms die, their shells are deposited as sediment and eventually turn into limestone. Limestones have accumulated over billions of years of geologic time and contain much of Earth's carbon. Ongoing research aims to speed up similar reactions involving alkali carbonates.

One proposed reaction is that of the olivine-rich rock dunite, or its hydrated equivalent serpentinite with carbon dioxide to form the carbonate mineral magnesite, plus silica and iron oxide (magnetite).

Serpentinite sequestration is favored because of the non-toxic and stable nature of magnesium carbonate. The ideal reactions involve the magnesium endmember components of the olivine (reaction 1) or serpentine (reaction 2), the latter derived from earlier olivine by hydration and silicification (reaction 3). The presence of iron in the olivine or serpentine reduces the efficiency of sequestration, since the iron components of these minerals break down to iron oxide and silica (reaction 4).

Serpentinite reactions

Reaction 1
Mg-Olivine + Carbon dioxide → Magnesite + Silica

Mg₂SiO₄ + 2CO₂ → 2MgCO₃ + SiO₂ + H₂O

Reaction 2
Serpentine + carbon dioxide → Magnesite + silica + water

Mg₃[Si₂O₅(OH)₄] + 3CO₂ → 3MgCO₃ + 2SiO₂ + 2H₂O

Reaction 3
Mg-Olivine + Water + Silica → Serpentine

3Mg₂SiO₄ + 2SiO₂ + 4H₂O → 2Mg₃[Si₂O₅(OH)₄

Reaction 4
Fe-Olivine + Water → Magnetite + Silica + Hydrogen

3Fe₂SiO₄ + 2H₂O → 2Fe₃O₄ + 3SiO₂ + 2H₂

Zeolitic imidazolate frameworks

Zeolitic imidazolate frameworks is a metal-organic framework carbon dioxide sink which could be used to keep industrial emissions of carbon dioxide out of the atmosphere.

Enhancing natural sequestration

noreply@blogger.com (Gen777) — Tue, 24 May 2011 16:14:00 +0000

Forests

Forests are carbon stores, and they are carbon dioxide sinks when they are increasing in density or area. In Canada's boreal forests as much as 80% of the total carbon is stored in the soils as dead organic matter. A 40-year study of African, Asian, and South American tropical forests by the University of Leeds, shows tropical forests absorb about 18% of all carbon dioxide added by fossil fuels. Tropical reforestation can mitigate global warming until all available land has been reforested with mature forests. However, the global cooling effect of carbon sequestration by forests is partially counterbalanced in that reforestation can decrease the reflection of sunlight (albedo). Mid-to-high latitude forests have a much lower albedo during snow seasons than flat ground, thus contributing to warming. Modeling that compares the effects of albedo differences between forests and grasslands suggests that expanding the land area of forests in temperate zones offers only a temporary cooling benefit.

In the United States in 2004 (the most recent year for which EPA statistics are available), forests sequestered 10.6% (637 teragrams) of the carbon dioxide released in the United States by the combustion of fossil fuels (coal, oil and natural gas; 5657 teragrams). Urban trees sequestered another 1.5% (88 teragrams). To further reduce U.S. carbon dioxide emissions by 7%, as stipulated by the Kyoto Protocol, would require the planting of "an area the size of Texas [8% of the area of Brazil] every 30 years". Carbon offset programs are planting millions of fast-growing trees per year to reforest tropical lands, for as little as $0.10 per tree; over their typical 40-year lifetime, one million of these trees will fix 0.9 teragrams of carbon dioxide. In Canada, reducing timber harvesting would have very little impact on carbon dioxide emissions because of the combination of harvest and stored carbon in manufactured wood products along with the regrowth of the harvested forests. Additionally, the amount of carbon released from harvesting is small compared to the amount of carbon lost each year to forest fires and other natural disturbances.

The Intergovernmental Panel on Climate Change concluded that "a sustainable forest management strategy aimed at maintaining or increasing forest carbon stocks, while producing an annual sustained yield of timber fibre or energy from the forest, will generate the largest sustained mitigation benefit". Sustainable management practices keep forests growing at a higher rate over a potentially longer period of time, thus providing net sequestration benefits in addition to those of unmanaged forests.

Life expectancy of forests varies throughout the world, influenced by tree species, site conditions and natural disturbance patterns. In some forests carbon may be stored for centuries, while in other forests carbon is released with frequent stand replacing fires. Forests that are harvested prior to stand replacing events allow for the retention of carbon in manufactured forest products such as lumber. However, only a portion of the carbon removed from logged forests ends up as durable goods and buildings. The remainder ends up as sawmill by-products such as pulp, paper and pallets, which often end with incineration (resulting in carbon release into the atmosphere) at the end of their lifecycle. For instance, of the 1,692 teragrams of carbon harvested from forests in Oregon and Washington (U.S) from 1900 to 1992, only 23% is in long-term storage in forest products.

Oceans

One way to increase the carbon sequestration efficiency of the oceans is to add micrometre-sized iron particles in the form of either hematite (iron oxide) or melanterite (iron sulfate) to certain regions of the ocean. This has the effect of stimulating growth of plankton. Iron is an important nutrient for phytoplankton, usually made available via upwelling along the continental shelves, inflows from rivers and streams, as well as deposition of dust suspended in the atmosphere. Natural sources of ocean iron have been declining in recent decades, contributing to an overall decline in ocean productivity (NASA, 2003). Yet in the presence of iron nutrients plankton populations quickly grow, or 'bloom', expanding the base of biomass productivity throughout the region and removing significant quantities of CO₂ from the atmosphere via photosynthesis. A test in 2002 in the Southern Ocean around Antarctica suggests that between 10,000 and 100,000 carbon atoms are sunk for each iron atom added to the water. More recent work in Germany (2005) suggests that any biomass carbon in the oceans, whether exported to depth or recycled in the euphotic zone, represents long-term storage of carbon. This means that application of iron nutrients in select parts of the oceans, at appropriate scales, could have the combined effect of restoring ocean productivity while at the same time mitigating the effects of human caused emissions of carbon dioxide to the atmosphere.

Because the effect of periodic small scale phytoplankton blooms on ocean ecosystems is unclear, more studies would be helpful. Phytoplankton have a complex effect on cloud formation via the release of substances such as dimethyl sulfide (DMS) that are converted to sulfate aerosols in the atmosphere, providing cloud condensation nuclei, or CCN. But the effect of small scale plankton blooms on overall DMS production is unknown.

Other nutrients such as nitrates, phosphates, and silica as well as iron may cause ocean fertilization. There has been some speculation that using pulses of fertilization (around 20 days in length) may be more effective at getting carbon to ocean floor than sustained fertilization.

There is some controversy over seeding the oceans with iron however, due to the potential for increased toxic phytoplankton growth (e.g. "red tide"), declining water quality due to overgrowth, and increasing anoxia in areas harming other sea-life such as zooplankton, fish, coral, etc.

Soils

Since the 1850s, a large proportion of the world's grasslands have been tilled and converted to croplands, allowing the rapid oxidation of large quantities of soil organic carbon. However, in the United States in 2004 (the most recent year for which EPA statistics are available), agricultural soils including pasture land sequestered 0.8% (46 teragrams) as much carbon as was released in the United States by the combustion of fossil fuels (5988 teragrams). The annual amount of this sequestration has been gradually increasing since 1998.

Methods that significantly enhance carbon sequestration in soil include no-till farming, residue mulching, cover cropping, and crop rotation, all of which are more widely used in organic farming than in conventional farming. Because only 5% of US farmland currently uses no-till and residue mulching, there is a large potential for carbon sequestration. Conversion to pastureland, particularly with good management of grazing, can sequester even more carbon in the soil.

Terra preta, an anthropogenic, high-carbon soil, is also being investigated as a sequestration mechanism. By pyrolysing biomass, about half of its carbon can be reduced to charcoal, which can persist in the soil for centuries, and makes a useful soil amendment, especially in tropical soils (biochar or agrichar).

Savanna

Controlled burns on far north Australian savannas can result in an overall carbon sink. One working example is the West Arnhem Fire Management Agreement, started to bring "strategic fire management across 28,000 km² of Western Arnhem Land". Deliberately starting controlled burns early in the dry season results in a mosaic of burnt and unburnt country which reduces the area of burning compared with stronger, late dry season fires. In the early dry season there are higher moisture levels, cooler temperatures, and lighter wind than later in the dry season; fires tend to go out overnight. Early controlled burns also results in a smaller proportion of the grass and tree biomass being burnt. Emission reductions of 256,000 tonnes of CO₂ have been made as of 2007.

Storage in terrestrial and marine environments

noreply@blogger.com (Gen777) — Tue, 24 May 2011 16:11:00 +0000

Soils

Soils represent a short to long-term carbon storage medium, and contain more carbon than all terrestrial vegetation and the atmosphere combined. Plant litter and other biomass accumulates as organic matter in soils, and is degraded by chemical weathering and biological degradation. More recalcitrant organic carbon polymers such as cellulose, hemi-cellulose, lignin, aliphatic compounds, waxes and terpenoids are collectively retained as humus. Organic matter tends to accumulate in litter and soils of colder regions such as the boreal forests of North America and the Taiga of Russia. Leaf litter and humus are rapidly oxidized and poorly retained in sub-tropical and tropical climate conditions due to high temperatures and extensive leaching by rainfall. Areas where shifting cultivation or slash and burn agriculture are practiced are generally only fertile for 2–3 years before they are abandoned. These tropical jungles are similar to coral reefs in that they are highly efficient at conserving and circulating necessary nutrients, which explains their lushness in a nutrient desert. Much organic carbon retained in many agricultural areas worldwide has been severely depleted due to intensive farming practices.

Grasslands contribute to soil organic matter, stored mainly in their extensive fibrous root mats. Due in part to the climactic conditions of these regions (e.g. cooler temperatures and semi-arid to arid conditions), these soils can accumulate significant quantities of organic matter. This can vary based on rainfall, the length of the winter season, and the frequency of naturally occurring lightning-induced grass-fires. While these fires release carbon dioxide, they improve the quality of the grasslands overall, in turn increasing the amount of carbon retained in the retained humic material. They also deposit carbon directly to the soil in the form of char that does not significantly degrade back to carbon dioxide.

Forest fires release absorbed carbon back into the atmosphere, as does deforestation due to rapidly increased oxidation of soil organic matter.

Organic matter in peat bogs undergoes slow anaerobic decomposition below the surface. This process is slow enough that in many cases the bog grows rapidly and fixes more carbon from the atmosphere than is released. Over time, the peat grows deeper. Peat bogs inter approximately one-quarter of the carbon stored in land plants and soils.

Under some conditions, forests and peat bogs may become sources of CO₂, such as when a forest is flooded by the construction of a hydroelectric dam. Unless the forests and peat are harvested before flooding, the rotting vegetation is a source of CO₂ and methane comparable in magnitude to the amount of carbon released by a fossil-fuel powered plant of equivalent power.

Regenerative agriculture

Current agricultural practices lead to carbon loss from soils. It has been suggested that improved farming practices could return the soils to being a carbon sink. Present worldwide practises of overgrazing are substantially reducing many grasslands performance as carbon sinks. The Rodale Institute says that Regenerative agriculture, if practiced on the planet’s 3.5 billion tillable acres, could sequester up to 40% of current CO₂ emissions. They claim that agricultural carbon sequestration has the potential to mitigate global warming. When using biologically based regenerative practices, this dramatic benefit can be accomplished with no decrease in yields or farmer profits. Organically managed soils can convert carbon dioxide from a greenhouse gas into a food-producing asset.

In 2006, U.S. carbon dioxide emissions from fossil fuel combustion were estimated at nearly 6.5 billion tons. If a 2,000 (lb/ac)/year sequestration rate was achieved on all 434,000,000 acres (1,760,000 km²) of cropland in the United States, nearly 1.6 billion tons of carbon dioxide would be sequestered per year, mitigating close to one quarter of the country's total fossil fuel emissions.

Oceans

Oceans are at present CO₂ sinks, and represent the largest active carbon sink on Earth, absorbing more than a quarter of the carbon dioxide that humans put into the air. On longer timescales they may be both sources and sinks - during ice ages CO₂ levels decrease to ~180 ppmv, and much of this is believed to be stored in the oceans. As ice ages end, CO₂ is released from the oceans and CO₂ levels during previous interglacials have been around ~280 ppmv. This role as a sink for CO₂ is driven by two processes, the solubility pump and the biological pump.^] The former is primarily a function of differential CO₂ solubility in seawater and the thermohaline circulation, while the latter is the sum of a series of biological processes that transport carbon (in organic and inorganic forms) from the surface euphotic zone to the ocean's interior. A small fraction of the organic carbon transported by the biological pump to the seafloor is buried in anoxic conditions under sediments and ultimately forms fossil fuels such as oil and natural gas.

At the present time, approximately one third of human generated emissions are estimated to be entering the ocean. The solubility pump is the primary mechanism driving this, with the biological pump playing a negligible role. This stems from the limitation of the biological pump by ambient light and nutrients required by the phytoplankton that ultimately drive it. Total inorganic carbon is not believed to limit primary production in the oceans, so its increasing availability in the ocean does not directly affect production (the situation on land is different, since enhanced atmospheric levels of CO₂ essentially "fertilize" land plant growth). However, ocean acidification by invading anthropogenic CO₂ may affect the biological pump by negatively impacting calcifying organisms such as coccolithophores, foraminiferans and pteropods. Climate change may also affect the biological pump in the future by warming and stratifying the surface ocean, thus reducing the supply of limiting nutrients to surface waters.

In January 2009, the Monterey Bay Aquarium Research Institute and the National Oceanic and Atmospheric Administration announced a joint study to determine whether the ocean off the California coast was serving as a carbon source or a carbon sink. Principal instrumentation for the study will be self-contained CO₂ monitors placed on buoys in the ocean. They will measure the partial pressure of CO₂ in the ocean and the atmosphere just above the water surface.

In February 2009, Science Daily reported that the Southern Indian Ocean is becoming less effective at absorbing carbon dioxide due to changes to the regions climate which include higher wind speeds.

Carbon Dioxide Sink

noreply@blogger.com (Gen777) — Tue, 24 May 2011 16:10:00 +0000

A carbon dioxide sink is a natural or artificial reservoir that accumulates and stores some carbon-containing chemical compound for an indefinite period. The process by which carbon sinks remove carbon dioxide (CO₂) from the atmosphere is known as carbon sequestration. Public awareness of the significance of CO₂ sinks has grown since passage of the Kyoto Protocol, which promotes their use as a form of carbon offset.

The main natural sinks are:

Absorption of carbon dioxide by the oceans via physicochemical and biological processes
Photosynthesis by terrestrial plants

Natural sinks are typically much larger than artificial sinks. The main artificial sinks are:

Landfills
Carbon capture and storage proposals

Carbon sources include:

Fossil fuels
Farmland; there are proposals for improvements in farming practices to reverse this.

Because growing vegetation absorbs carbon dioxide, the Kyoto Protocol allows Annex I countries with large areas of growing forests to issue Removal Units to recognise the sequestration of carbon. The additional units make it easier for them to achieve their target emission levels.

Some countries seek to trade emission rights in carbon emission markets, purchasing the unused carbon emission allowances of other countries. If overall limits on greenhouse gas emission are put into place, cap and trade market mechanisms are purported to find cost-effective ways to reduce emissions. There is as yet no carbon audit regime for all such markets globally, and none is specified in the Kyoto Protocol. National carbon emissions are self-declared.

In the Clean Development Mechanism, only afforestation and reforestation are eligible to produce certified emission reductions (CERs) in the first commitment period of the Kyoto Protocol (2008–2012). Forest conservation activities or activities avoiding deforestation, which would result in emission reduction through the conservation of existing carbon stocks, are not eligible at this time. Also, agricultural carbon sequestration is not possible yet.