Biochar made of chicken waste and wood chips from Josh Frye’s farm in Wardensville, West Virginia.

Credit: Jeff Hutchins / Getty

Biochar

Call to action:

Turn biowaste into biochar, which can last a thousand years, and use it to build soil health and sequester carbon.

Biochar has ancestral roots in the Amazon and Africa, where people have long used charred wood as part of an agricultural practice to create soil called terra preta, or “dark earth.” Burying biochar—essentially charcoal created for purposes other than burning—creates a home for microbes, minerals, and water. In acidic, nutrient-poor, and/or sandy soil, biochar can increase crop yields and reduce fertilizer and irrigation needs. Biochar has important benefits for climate change. It can reduce agricultural greenhouse gases from livestock or soils. Biochar production can avoid emissions from open burning or decay of biowaste from forests or farms. If produced carefully and buried for long periods of time biochar stores more carbon than it creates.

Action Items

Individuals

Learn about the potential of biochar and its complexities. Biochar is created by pyrolysis, a process of heating organic matter to a high temperature while limiting the oxygen that would cause it to burn. The organic matter chars instead, capturing about 70 percent of the original carbon. The resulting biochar is porous and attracts substances from ammonia to zinc, making it useful for filtering water, removing contaminants, and amending soil. Because it is very stable, biochar can sequester carbon for hundreds or thousands of years, though its climate impact varies depending on what materials and processes are used to make it.

Traditionally biochar, like charcoal, has been made in kilns or pits, but they emit greenhouse gases, including methane and nitrous oxide. Today, retort kilns and easy-to-build flame-curtain kilns partially burn these gases. The production methods that have the best climate impact are pyrolyzing cookstoves and gasifier plants that not only burn the gases but use the heat for cooking or energy production.
Biochar is highly variable depending on its feedstock, which can include nearly any biomass: wood from forests, agriculture, or cities; cornstalks, rice hulls, palm husks, and other agricultural waste; and manure. Biochar using woody material tends to be more stable for sequestering carbon.
Producing biochar not only avoids greenhouse gas emissions, it reduces air pollution from crop burning and forest fires when it’s done to process agricultural waste or forest thinnings (small-diameter low-value trees cut to reduce fuel in forests).
Biochar-producing cookstoves in Africa and Bangladesh reduce emissions from cooking, improve health, reduce fuel use, and provide a soil amendment (see Clean Cookstoves Nexus).
Biochar takes up pollutants from water and can be used to build simple, inexpensive water filters from local materials.
Biochar is not a simple fix. Large-scale biochar production carries risks of deforestation. Producing it can release greenhouse gases, and in some cases it can increase methane and nitrous oxide emissions from soil.

Use biochar to enrich your garden soils or compost. Look for companies or organizations that specifically use biowaste rather than farmed wood to produce their biochar, such as Rosy Soil or Local Carbon Network. The US Biochar Initiative has a list of North American suppliers.

Prioritize biochar for sandy, acidic, or low-fertility/low-carbon soils. If your soil is clayey, alkaline, or highly fertile, you may not see benefit and may even have lower yields, although it can improve water-holding capacity in clay as well.
Enhance your compost with biochar for improved texture and nutrient and water capacity.
Charge or activate biochar with compost tea, manure, or worm castings and use recommended application amounts and techniques.

Become part of a biochar community with a Local Carbon Network to produce biochar, compost it, and use it in community gardens. If you produce five tons of woody waste per month you can become a biochar-producing node. You can also commit to using biochar in your compost and get monthly supplies, or volunteer at a local garden.

Replace your barbecue with a biochar stove for outdoor cooking (not briquettes!). Top-lit updraft gasifier (TLUD) stoves have low emissions and are simple to make. You can also buy different models of gasifier stoves. If you want to produce larger quantities of biochar, see Producers below.

Sponsor biochar-producing clean cookstoves through Clean Cooking Revolution, whose highly efficient stoves use wood pellets that can be locally produced.

Help research biochar. Citizen science, in which volunteers collect data scientists need, is a powerful tool for better understanding biochar’s complexities.

Bury small bags of biochar to help Kurt Spokas of the USDA to understand how biochar changes over time in soil.

Groups

Land Managers

Reduce emissions and air pollution by producing biochar with forest thinnings instead of using burn piles. Using simple, portable kilns reduces risk of fire, preserves soils, reduces pollution, and creates biochar instead of ash.

Wilson Biochar features a number of example projects on the West Coast.
The US Biochar Initiative’s Learning Database has a number of papers and presentations on field-ready techniques.
UC Merced is piloting a portable pyrolizer.

Farmers/Ranchers

Use biochar to improve soil, reduce irrigation needs, and improve plant and animal health. Different biochars are effective for different uses. It is important to consider your soil, crops, and the biochar you intend to use when deciding when and how to use it. This synthesis is a good introduction to how biochar interacts with soils, while this manual explains applications.

Improve soil fertility in acidic, low-fertility soils. Biochar increases soil pH and adds nutrients, with its effects especially notable in the tropics. In neutral, high-fertility soils, biochar may be substituted for lime.
Increase cation exchange capacity (CEC) for improved nutrient retention. Analysis of terra preta soils showed improved CEC compared to adjacent soils. Studies of different biochars show type of feedstock is most important for cation exchange capacity, with temperature next in influence. Lower temperatures typically showed higher CEC.
Save irrigation costs for sandy soils—potentially one third or more of irrigation costs. Biochar application can increase drought resilience by improving available water content, especially in coarse soils. In clay soils biochar decreases runoff. Sandy, acidic soils with low carbon content showed greatest improvement in available water content.
Improve crop yields and soil health by utilizing biochar-based fertilizer. In vineyards, ten tons of compost with fifteen tons of biochar per acre on sandy soil increased grape production by two tons per acre, also increasing profits.
Reduce soil emissions of nitrous oxide with biochar. Biochar application to soils can halve emissions of nitrous oxide (N₂O), a long-lived greenhouse gas. Some studies have found increases in N₂O, although these may be short-term spikes with no long-term effects.
Reduce soil emissions of methane with biochar, especially flooded soils such as rice paddies.
Keep cattle and poultry healthier and reduce methane emissions by adding biochar to animal feed. Biochar has been used in animal feed for many years to absorb toxins in feed and digestive tracts, improve animal health and growth, and reduce methane emissions from cattle. European farmers see reduced veterinary costs from use of biochar.
Stack uses of biochar for multiple benefits. Doug Pow, an Australian rancher, fed his cattle biochar as a way to distribute biochar in his soil. Improved soil fertility and herd health lowered costs and increased profits.
Mix biochar with manure at 10 to 20 percent biochar to manure by weight to reduce methane release from the manure. This can also reduce nitrous oxide and ammonia release.

Work with biochar producers or researchers to dispose of crop waste. See Producers below or Land Managers above for examples.

Biochar Producers

Fine-tune biochar kilns to reduce emissions. Methane from some kilns can negate the short-term effect of biochar carbon sequestration. Make kilns that take into account best practices:

Best climate impact comes from gasifiers or pyrolyzing cookstoves because they combine biochar production with usable energy or heat.
Flame-curtain kilns are climate neutral.
Kon-Tiki kilns and traditional earth kilns have high methane emissions.

Source your feedstock from waste materials. Life-cycle analysis of biochar showed that biowaste feedstock, instead of biomass grown for biochar production, is essential to making biochar a negative emissions technology.

Pacific Biochar uses sawmill and logging residues from sustainably managed forests.
Carboculture creates biochar from California’s agricultural waste.
Kenyan farmers use gasifier cookstoves to produce biochar from a variety of sources, including tree pruning and corn (maize) cobs.

Produce and label according to quality and ingredient standards to enable consumers to compare biochars and select the best for their needs.

The International Biochar Initiative certifies biochar made in the United States and Canada.
The US Biochar Initiative has labeling guidance for biochar as a soil amendment.
The European Biochar Certification is a voluntary quality standard.

Adhere to sustainability protocols so your biochar is socially, environmentally, and economically responsible. The US Biochar Initiative and the International Biochar Initiative both have protocols. Elements include:

Greenhouse gas reduction or neutrality through the life cycle
Maintaining biodiversity
Maintaining food security (not displacing food-growing land uses)
Involving local communities
Fair labor practices

Perform life-cycle analysis on your process and be transparent about the results. Only a thorough analysis of greenhouse gases from biochar production and use, preferably with standardized methodology, can show that your biochar is truly a negative emissions technology (see Researchers below).

This study of a gasification plant in Italy provides a framework for analysis, including uncertainties.
Rosy Soil relied on this methodology to produce a life-cycle analysis for its biochar-containing potting soil.

Acknowledge the traditional roots of biochar and explore fair compensation models to Indigenous peoples. The popularity of biochar is based on Indigenous techniques, and business models for producing biochar may even capitalize on the term terra preta. Yet large-scale biochar production potentially harms the people who showed the way.

Don’t attempt to patent biochar or soil amendments. Biochar patenting is a form of biopiracy that profits from indigenous knowledge without compensation.
Support Indigenous communities that originated biochar. Initiatives like Amazonia 80 X 2025 or African Biodiversity Network support Indigenous peoples and their agricultural practices.

Local Governments

Invest in biochar solutions to handle green waste, draw down carbon, and provide citizens with multiple benefits. Biochar avoids transportation costs and emissions when feedstock is processed close to the source, so it can be an important climate lever for local governments.

Stockholm utilizes a biochar plant to use tree trimmings and yard waste to heat homes, then adds the resulting biochar to soil to absorb storm water and increase fertility.
Minneapolis is exploring the feasibility of a local biochar plant and piloting small projects to see how biochar can improve the city, while mixing biochar with compost to improve agricultural production.
Boulder County, Colorado, and Flagstaff, Arizona, are part of a coalition attempting to draw down carbon and put climate solutions in the hands of communities; they see biochar from forest thinnings as one potential solution.

Listen to and work with Indigenous peoples. Indigenous groups in the Amazon and in Africa have produced dark earths or terra preta for centuries by burying the remains from cooking fires in middens with household waste. Their expertise in pyrogenic carbon should be consulted, and they can benefit from truly cooperative research.

Companies

Invest in biochar solutions for medium- and long-term carbon sequestration. Because biochar can sequester carbon for long periods of time, it addresses the challenge of permanence that compromises many nature-based sequestration efforts, including those used by companies to offset greenhouse gas emissions. However, biochar projects must also have additionality to be effective (i.e., they need to sequester carbon that was not already being sequestered). Certifying bodies have struggled to create a protocol for biochar projects, and projects that have been certified do not necessarily provide additionality. However, Charm Industrial and Takachar are among especially promising projects (see Onsets Nexus).

Governance

Include biochar in organic standards and feed standards. Many organic standards support the use of biochar, although they may not have a standard for the biochar itself. The EU has strict standards for biochar as an animal feed additive, allowing it in organic feed and limiting the amount of heavy metals in biochar as feed.

Support research into biochar as a nature-based carbon capture mechanism. The United Kingdom is investing several million pounds into researching biochar in several different land-use cases.

Support potential users and biochar producers entering the market. In an emerging market, biochar producers can benefit from policy, technical, and monetary support.

The Nebraska Forest Service’s Great Plains Biochar Initiative provides technical assistance, workshops, and grants to people interested in using biochar or making it, focusing on agricultural use and thinning aggressive species.
Washington State made a grant to a nonprofit start-up, C6 Forest to Farm, piloting biochar production as a means to support forest restoration as well as to sequester carbon.