Carbon farming
Carbon farming is a set of agricultural methods that aim to store carbon in the soil and biomass. The technical term for this process is carbon sequestration. The overall goal of carbon farming is to create a net loss of carbon from the atmosphere. This is done by increasing the rate at which carbon is sequestered into soil and plant material. The increase of biomass from roots and the soil's microbiome leads to an increase in the organic matter content of the soil. Increasing organic matter content in soils aids plant growth, improves soil water retention capacity and reduces fertilizer use. Sustainable forest management is another tool that is used in carbon farming. Carbon farming is one component of climate-smart agriculture. It is also one way to remove carbon dioxide from the atmosphere.
Compared to natural vegetation, cropland soils are depleted in soil organic carbon. When a soil is converted from natural land or semi natural land, such as forests, woodlands, grasslands, steppes and savannas, the SOC content in the soil reduces by about 30, 40%. The loss of carbon through agricultural practices can eventually lead to the loss of soil suitable for agriculture. The carbon loss from the soil is due to the removal of plant material containing carbon, via harvesting. When land use changes, soil carbon either increases or decreases. This change continues until the soil reaches a new equilibrium. Deviations from this equilibrium can also be affected by varying climate. The decrease can be counteracted by increasing carbon input. This can be done via several strategies, e.g. leaving harvest residues on the field, using manure or rotating perennial crops. Perennial crops have a larger below ground biomass fraction, which increases the SOC content. Globally, soils are estimated to contain >8,580 gigatons of organic carbon, about ten times the amount in the atmosphere and much more than in vegetation. In part, soil carbon is thought to accumulate when decaying organic matter was physically mixed with soil. Small roots die and decay while the plant is alive, depositing carbon below the surface. More recently, the role of living plants has been emphasized where carbon is released as plants grow. Soils can contain up to 5% carbon by weight, including decomposing plant and animal matter and biochar. About half of soil carbon is found within deep soils. About 90% of this is stabilized by mineral, organic associations.
Forestry and agriculture are both land-based human activities that add up to contribute approximately a third of the world's greenhouse gas emissions. There is a large interest in reforestation, but in regards to carbon farming most of that reforestation opportunity will be in small patches with trees being planted by individual land owners in exchange for benefits provided by carbon farming programs. Forestry in carbon farming can be both reforestation, which is restoring forests to areas that were deforested, and afforestation which would be planting forests in areas that were not historically forested. Not all forests will sequester the same amount of carbon. Carbon sequestration is dependent on several factors which can include forest age, forest type, amount of biodiversity, the management practices the forest is experiences and climate. Biodiversity is often thought to be a side benefit of carbon farming, but in forest ecosystems increased biodiversity can increase the rate of carbon sequestration and can be a tool in carbon farming and not just a side benefit. A bamboo forest will store less total carbon than most types of mature forest. However, it can store a similar total amount of carbon as rubber plantations and tree orchards, and can surpass the total carbon stored in agroforests, palm oil plantations, grasslands and shrublands. A bamboo plantation sequesters carbon at a faster rate than a mature forest or a tree plantation. However it has been found that only new plantations or plantations with active management will be sequestering carbon at a faster rate than mature forests. Compared with other fast-growing tree species, bamboo is only superior in its ability to sequester carbon if selectively harvested. Bamboo
forests are especially high in potential for carbon sequestration if the cultivated plant material is turned into durable products that keep the carbon in the plant material for a long period because bamboo is both fast growing and regrows strongly following an annual harvest.
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 atmospheric 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. Carbon farming methods might have additional costs. Individual land owners are sometimes given incentives to use carbon farming methods through government policies. Governments in Australia and New Zealand are considering allowing farmers to sell carbon credits once they document that they have sufficiently increased soil carbon content. Approved practices may make farmers eligible for federal funds. Not all carbon farming techniques have been recommended. A 2013 study found that a single compost application significantly and durably increased grassland carbon storage by 25, 70%. The continuation sequestration likely came from increased water-holding and fertilization by compost decomposition. Both factors support increased productivity. Both tested sites showed large increases in grassland productivity: a forage increase of 78% in a drier valley site, while a wetter coastal site averaged an increase of 42%. Another study found that grasslands treated with .5 inches of commercial compost began absorbing carbon at an annual rate of nearly 1.5 tons/acre and continued to do so in subsequent years. As of 2018, this study had not been replicated.
In 2011 Australia started a cap-and-trade program. Farmers who sequester carbon can sell carbon credits to companies in need of carbon offsets. The country's Direct Action Plan states The single largest opportunity for CO2 emissions reduction in Australia is through bio-sequestration in general, and in particular, the replenishment of our soil carbons.
In studies of test plots over 20 years showed increased microbial activity when farmers incorporated organic matter or reduced tillage. Soil carbon levels from 1990 to 2006 declined by 30% on average under continuous cropping. Incorporating organic matter alone was not enough to build soil carbon. Nitrogen, phosphorus and sulphur had to be added as well to do so. By 2014 more than 75% of Canadian Prairies' cropland had adopted conservation tillage and more than 50% had adopted no-till. Twenty-five countries pledged to adopt the practice at the December 2015 Paris climate talks. The Canadian government has allocated CAD$885M to spend between 2021-31 on adopting climate solutions in agriculture as part of the CAD$2B Natural Climate Solutions Fund. The largest international effort to promote carbon farming is four per 1,000, led by France. Its goal is to increase soil carbon by 0.4% per year through agricultural and forestry changes. In 2016, France implemented a cap on the amount of energy crops that could be used to produce biofuels to limit competition with food crop production. Cover crops are exempted from this cap in order to create a financial incentive to adopt cover cropping. A public-private partnership project, Agroimpact, has been launched in French-speaking part of Switzerland. It advises farmers on how to sequester carbon and compensates them based on the CO2 emissions avoided
as a result. Funding is provided by stakeholders in the agri-food sector who pay a premium to farmers, enabling them to improve their own carbon footprint.
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Common questions
What is carbon farming and how does it work?
Carbon farming is a set of agricultural methods that aim to store carbon in the soil and biomass through the process known as carbon sequestration. This method increases the rate at which carbon is captured into plant material and soil organic matter to create a net loss of carbon from the atmosphere.
How much carbon do global soils contain compared to the atmosphere?
Globally, soils are estimated to contain more than 8580 gigatons of organic carbon, which is about ten times the amount found in the atmosphere. About half of this soil carbon exists within deep soils where approximately 90% is stabilized by mineral and organic associations.
When did Australia start its cap-and-trade program for carbon credits?
Australia started a cap-and-trade program in 2011 that allows farmers who sequester carbon to sell carbon credits to companies needing offsets. The country's Direct Action Plan identifies bio-sequestration and the replenishment of soil carbons as the single largest opportunity for CO2 emissions reduction.
Which countries have implemented specific policies or funds for carbon farming?
Governments in Australia and New Zealand are considering allowing farmers to sell carbon credits after documenting increased soil carbon content. Canada allocated CAD$885M between 2021 and 2031 to adopt climate solutions in agriculture under the Natural Climate Solutions Fund while France leads the four per 1,000 initiative to increase soil carbon by 0.4% annually.
How does bamboo compare to other forests in terms of carbon sequestration rates?
A bamboo forest stores less total carbon than most mature forests but can surpass agroforests, palm oil plantations, grasslands, and shrublands in total stored carbon. Bamboo plantations sequester carbon at a faster rate than mature forests when they are new or actively managed with selective harvesting practices.