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Carbon Sequestration Certification Program

Frequently Asked Questions (FAQs) 

Click here to view the glossary.

Click here for a page of links to additional information.


Q: What is the carbon baseline of the U.S.?

A: In the late 1990s scientists estimated the amount of carbon dioxide being emitted in the United States. To do this they estimated the amount of CO2 being emitted from various sources, including power plants, automobiles, and agriculture. The quantity of CO2 the researchers arrived at is considered the baseline for the United States. Since that time, one method of determining if a carbon offset is "additional" requires that the reduction in CO2 must have occurred since the baseline was determined and be measured relative to that baseline. Agricultural carbon offsets are held to the baseline standard with only those offsets resulting in a net reduction of the historic baseline amount of CO2 qualifying as a true carbon offset. For more information, read the online article Depositing Carbon in the Bank, the Soil Bank, that is.


Q: What is a carbon "sink"?

A: A carbon sink absorbs more carbon than it emits. By comparison, a carbon source emits more than it absorbs. For example, your car emits CO2 and a field of grass absorbs CO2.


Q: What is Cap-and-Trade?

A: Emissions allowance trading occurs when an emitter wants to voluntarily reduce its emissions or is forced to reduce emissions as a result of a cap-and-trade system, which places maximum limits on the amount of greenhouse gases an emitter or business sector may emit. Cap-and-trade systems force an emitter to purchase additional emission allowances from another emitter that is not emitting its maximum allocation of gases, or to mitigate its excess emissions by buying or generating greenhouse gas offsets from a project that is reducing emissions through some activity, such as agriculture, forestry, or injection of carbon dioxide underground.


Q: How much CO2 is stored in vegetation and soils?

A: Vegetation and soils are widely recognized as carbon storage sinks. The global biosphere absorbs roughly 2 billion tons of carbon annually, an amount equal to roughly one third of all global carbon emissions from human activity.

Source: DOE “Terrestrial Sequestration Research”


Q: How much CO2 is produced by power plants?

A: A typical coalfired power plant will produce about one ton of CO2 for every megawatt hour of electricity that it generates. A typical power plant using natural gas emits about one-half ton of CO2 per megawatt hour.

Source: Benchmarking Air Emissions of 100 Largest Electric Power Producers in the U.S. 2006


Q: How much CO2 is emitted by different sectors?

A: Electricity generation accounts for approximately 38% of all carbon dioxide emissions in the United States; Transportation accounts for 27% of all GHG emissions in the United States; Agriculture contributes approximately 7% of total U.S. GHG emissions, with nitrous oxide (N2O) accounting for two-thirds and methane (CH4) for one-third of agricultural emissions.


Q: How much CO2 is stored by trees in the U.S.?

A: Forests and trees account for a majority (94%) of all estimated carbon uptake in the United States, mostly through forest restoration and tree-planting. Carbon uptake in soils on U.S. agricultural lands accounts for the remainder.

Source: Climate Change: The Role for the U.S. Agriculture Sector (CRS Report to Congress). Author: Renee Johnson, Analyst in Agricultural Economics, Resources, Science, and Industry Division. March 2007.


Q: What does melting permafrost have to do with CO2 ?

A: Permafrost is frozen ground that contains roots and other soil organic matter that decompose extremely slowly. When it thaws, bacteria and fungi break down carbon contained in this organic matter much more quickly, releasing it to the atmosphere as carbon dioxide or methane, both greenhouse gases.

Q: What is the terrestrial carbon cycle?

A: Carbon cycles between the land and the atmosphere. Plants remove CO2 from the atmosphere during photosynthesis. The plants convert the carbon (C) into stems, stalks, leaves, and roots while the oxygen (O2) is released back to the atmosphere. Over time, some of the carbon moves from the roots into the soil where it provides vital nutrients to the growing plant. Because plants are carbon, decaying plants add carbon to the soil and make a good mulch or soil amendment for this reason. Even though decaying organic matter releases CO2 to the atmosphere, it does so much more slowly when left undisturbed on or in the soil. Researchers say carbon can remain stored in undisturbed soils for thousands of years. However, when soil is turned over, the carbon is released back into the atmosphere.


Q: What is the link between carbon storage and water quality?

A: Scientists estimate that up to 60% of the carbon has been lost from soils since the agricultural expansion of the 1800s. This loss is mostly a result of traditional tillage practices that turn the soil over and expose it to air. Changes in farming practices such as farming with no-till, sustainable grazing of livestock, and grassland and rangeland management optimize plant growth while requiring minimal soil disturbance, which helps restore carbon to the soil. These same conservation practices also protect water and air quality because when the soil is held in place by plants it is not eroding into waterways or blowing in the wind.


Q: How do plants and soil sequester carbon?

A: Terrestrial (land) ecosystems remove atmospheric carbon dioxide by plant photosynthesis during the day, which results in plant growth (roots and shoots) and increases in microbial biomass in the soil. Plants release some of the stored carbon back into the atmosphere through respiration. When a plant sheds leaves and roots die, this organic material decays, but some of it can be protected physically and chemically as dead organic matter in soils, which can be stable for up to thousands of years. The decomposition of soil carbon by soil microbes releases carbon dioxide to the atmosphere. This decomposition also mineralizes organic matter, which makes nutrients available for plant growth. The total amount of carbon stored in an ecosystem reflects the long-term balance between plant production and respiration and soil decomposition.

Source: Oak Ridge National Laboratory (ORNL)


Q: How does carbon get into soil?

A: On agricultural lands, carbon can enter the soil through roots, litter, harvest residues, and animal manure, and may be stored primarily as soil organic matter. Soils can hold carbon both underground in the root structure and near the soil surface and in plant biomass.

Q: Does soil really hold much carbon? 

A: Soils are estimated to contain about 75% of all terrestrial carbon. Because 25 billion tons of soils are lost through wind and water erosion each year, there is an incentive to prevent erosion not only to benefit agriculture but also to increase carbon sequestration. One solution is to produce and protect soils high in carbon-containing organic matter because they have better texture and are better able to absorb nutrients, retain water, and resist erosion.

Source: Oak Ridge National Laboratory (ORNL)


Q: How much carbon can be sequestered in agricultural soils?

A: Actual carbon uptake in agricultural soils depends on several site specific factors, including location, climate, land history, soil type, type of crop or vegetation, planting area, tillage practices, crop rotations and cover crops, and farm management in implementing certain conservation and land management practices.

Source: Climate Change: The Role for the U.S. Agriculture Sector (CRS Report to Congress). Author: Renee Johnson, Analyst in Agricultural Economics, Resources, Science, and Industry Division. March 2007.


Q: How effectively do conservation practices sequester carbon in plants and soil?

A: In general, the effectiveness of adopting conservation and land management practices will depend on the type of practice, how well the practice is implemented, and also on the length of time a practice is undertaken. For example, time is needed for a certain conservation practice to take hold and for benefits to accrue, such as buildup of carbon in soils from implementing conservation tillage or other soil management techniques, and growing time for cover crops or vegetative buffers. The overall length of time the practice remains in place is critical, especially regarding the sequestration benefits that accrue over the time period in which land is retired. In addition, not all conservation and land management practices are equally effective or appropriate in all types of physical settings. For example, the use and effectiveness of conservation tillage practices will vary depending on soil type and moisture regime, which may discourage some farmers from adopting or continuing this practice in some areas.

Source: Climate Change: The Role for the U.S. Agriculture Sector (CRS Report to Congress). Author: Renee Johnson, Analyst in Agricultural Economics, Resources, Science, and Industry Division. March 2007.


Q: Why is no-till a recommended practice for soil carbon programs?

In the past 100 years, intensive agriculture has caused a soil carbon loss of 30%-50%, mostly through traditional tillage practices. In contrast, conservation tillage practices preserve soil carbon by maintaining a ground cover after planting and by reducing soil disturbance compared with traditional cultivation, thereby reducing soil loss and energy use while maintaining crop yields and quality. No till reduces oxidation and the release of carbon into the atmosphere. Therefore, conservation tillage practices reduce emissions from cultivation and also enhance carbon sequestration in soils. Nearly 40% of U.S. planted areas are under some type of conservation tillage practices.

Source: Climate Change: The Role for the U.S. Agriculture Sector (CRS Report to Congress). Author: Renee Johnson, Analyst in Agricultural Economics, Resources, Science, and Industry Division. March 2007.


Q: How is the sequestration rate for no-till calculated?

A: Sequestration rates have been determined by soil carbon research and modeling done over the last decade. Those rates have been applied to regions of the U.S. and are considered conservative to allow for variances in soils and climate, which affect the rate and length of time that carbon is sequestered in soils. 


Q:Why are dates, such as 1999, often used as cutoffs for carbon offset credits?

To determine any success in GHG reduction, a base level of atmospheric CO2 was established during the period 1998 – 2000. Therefore, carbon sequestering practices eligible for the offset program must have been established after 1999 to be able to effectively measure their impact on GHG reduction.

Source: Illinois Conservation Climate Initiative


Q: Why doesn’t land that has been in conservation tillage for a decade or more, and has more carbon stored, earn more than land just enrolled in conservation tillage and has less carbon stockpiled. 

A:  Current research hasn't discovered a way to account fairly for the long-stored carbon. Values are based on research, and the organic content of soils can reach a saturation point, which varies by soil type. 


Q: Why are standards necessary in carbon programs?

A: To give certainty to buyers that the offset is real and sequestering the amount of carbon claimed. 


Q: Who buys carbon offsets?

A: The vast majority of credit buyers in the 2007 voluntary markets were private businesses (79%). Approximately two-thirds of their credits were purchased to immediately offset emissions, with the remaining third bought for investment purposes.

Source: State of the Voluntary Carbon Market 2008


Q: How does someone choose what kind of carbon offsets to buy?

A: For voluntary purchases, “additionality” - the demonstrable ability to reduce emissions beyond the levels that would otherwise have occurred – remained the primary criteria for selecting an offset provider in 2007, consistent with 2006. Environmental and social co-benefits were also ranked highly.

Source: State of the Voluntary Carbon Market 2008


Q: What are the downsides of soil carbon sequestration projects?

A: The potential impermanence of conservation and land management practices raises concerns about the effectiveness and limited storage value of the types of conservation practices that sequester carbon, given that the amount of carbon stored depends on the willingness of landowners to adopt or continue to implement a particular voluntary conservation practice.

Source: Climate Change: The Role for the U.S. Agriculture Sector (CRS Report to Congress). Author: Renee Johnson, Analyst in Agricultural Economics, Resources, Science, and Industry Division. March 2007.

Last Modified on 01/21/2011