Biochar and Compost for Climate Change Adaptation and Mitigation | Article

The climate crisis and years of unsustainable farming in the United States have resulted in soil erosion, pollinator loss, farmworkers and livestock exposed to extreme heat, and other harmful impacts. In 2019, 10 percent of U.S. greenhouse gas emissions came from agriculture. At the same time, farmers and the land they work are vulnerable to climate impacts such as drought and extreme weather.

Sustainable soil amendments such as biochar and compost are among the many agricultural practices that can help farmers mitigate and adapt to the climate crisis. This is the final article in EESI’s five-part series on sustainable agricultural practices including cover crops, agroforestry, no-till farming, sustainable livestock grazing, and soil amendments.

What are Soil Amendments?

Soil amendments are products added to soil that enhance desired characteristics such as nutrient content, texture, and fertility. There are a wide variety of soil amendments available, but only some provide climate change mitigation and adaptation benefits, namely biochar and compost.

Biochar is a carbon-rich amendment similar to charcoal that is created by combusting organic waste materials (e.g. stems, husks, and wood waste) under low-oxygen conditions. The resulting product stores carbon in a stable form that prevents it from breaking down to release carbon dioxide. According to the U.S. Department of Agriculture (USDA), using biochar as a soil amendment improves soil health, raises soil pH to make nutrients more soluble, remediates polluted soil, sequesters carbon, lowers greenhouse gas emissions, and improves soil moisture.
Compost is another soil amendment produced from the decomposition of organic matter like food waste, yard waste, and animal manure under high temperatures. It is rich in nutrients such as nitrogen, potassium, and phosphorus and provides a plethora of soil benefits, including reduced erosion, increased micronutrients and microbial activity, and enhanced water holding capacity.

Fighting Climate Change with Biochar and Compost

During EESI's recent briefing on direct air capture (DAC), panelist Dr. Kevin O'Brien, director of the Illinois Sustainable Technology Center & Illinois State Water Survey, stated that researchers are studying how to use the carbon that is captured from DAC facilities to grow algae. That algae can then be harvested and turned into biochar.

Soil amendments like biochar and compost transform agricultural waste materials into products that return carbon to the soil. When agricultural waste is used to make biochar, the carbon in those materials is locked in, thus preventing it from being released into the atmosphere. Biochar can be applied to the soil on its own or added to compost for additional benefits. According to Nature4Climate, converting agricultural residues to biochar globally could prevent the release of 331 million tonnes of carbon dioxide equivalent, the same amount of emissions produced by more than 88 coal-fired power plants in one year. However, additional research is needed to better understand the emissions reduction benefits of biochar and ensure that biochar dust does not post hazards to human health.

Compost also offers climate change mitigation benefits. When organic waste is sent to a landfill, it produces greenhouse gas emissions like methane, which is 80 times more powerful than carbon dioxide in the near-term. It is estimated that the annual greenhouse gas emissions of food waste in the United States is equal to 42 coal-fired power plants. Diverting food and other organic waste from the landfill by turning it into compost can significantly reduce these emissions, especially methane. Additionally, applying compost as a soil amendment improves soil health and strengthens its microbiome, which increases the soil’s ability to store carbon.

Building Climate Resilience

Biochar and compost can help build resilience to climate change on farms and ranches across the country. They improve the water-holding capacity and filtration of soil so that it can better withstand drought, heat waves, and heavy rains, all of which are becoming more severe and frequent due to climate change. Additionally, biochar and compost improve overall soil health and biodiversity, resulting in healthier crops that are more resistant to disease and pests.

Soil amendments can also protect ecosystems from pollutants. For instance, compost can improve downstream water quality by retaining pollutants like heavy metals and nitrogen, reducing erosion, and minimizing the need for synthetic fertilizer. Both compost and biochar have been used to remediate contaminated soil, which further strengthens overall ecosystem health.

Improving Crop Yields

By increasing the organic matter in soil, biochar and compost can increase crop and forage yields, which is often a driving reason for adding them to agricultural systems. Organic soil amendments also reduce the need for synthetic fertilizers, which can save producers money and further reduce greenhouse gas emissions.

Biochar in Action: Reducing Wildfire Fuel in Oregon

Oregon and many other parts of the western United States are prone to severe wildfires. Thinning forests and vegetated areas can help reduce this risk by limiting the availability of “fuel,” but the process results in wood waste that cannot be used for traditional commercial purposes. Additionally, many small farms have difficulties with disposing animal waste. To address these issues together, in 2015, the USDA Natural Resources Conservation Service (NRCS) awarded a Conservation Innovation Grant (CIG) to the South Umpqua Rural Community Partnership in Oregon to transform waste products like animal manure and woody debris into biochar.

The CIG project aimed to help farmers and forest landowners reuse their waste by turning it into biochar directly on their property using small-scale kilns, thus avoiding the financial strain of transporting the materials offsite. Landowners participating in the project designed kilns sized for the needs of their properties, and welding students from the local Umpqua Community College helped craft them.

After two and a half years, participants in the study were able to economically produce biochar and either use it onsite as a soil amendment or sell it. Many of the participants also cited a reduction in odors from animal waste. While the process requires slightly more work compared to burning or disposing of the waste, one participant said that “making biochar is 20 percent more work for twice the volume of compost.”

One of the most important outcomes of the CIG project was that it resulted in a new enhancement to the USDA Conservation Stewardship Program (CSP) that allows forestry participants to convert woody debris into biochar. A CSP participant in Oregon has since been using the enhancement to restore oak habitats by removing other competing trees and using the woody biomass to make biochar.

Federal Programs That Support Biochar and Compost

Several programs within the USDA bolster biochar and composting activities, including:

The BioPreferred Program is intended to increase the purchase of biobased products and includes mandatory purchasing requirements for the federal government. The program includes biochar and composted products.
The Conservation Stewardship Program (CSP) within USDA’s NRCS helps farmers and agricultural producers maintain, improve, or adopt new conservation practices, such as producing biochar from woody residue.
Conservation Innovation Grants (CIG) within USDA’s NRCS support the development of new natural resource conservation methods and have been used to develop more effective biochar and composting systems.
Composting and Food Waste Reduction (CFWR) cooperative agreements assist local and municipal governments in planning and implementing compost and food waste reduction plans.
The Environmental Quality Incentives Program (EQIP) provides financial and technical assistance for projects that address natural resource concerns and provide environmental benefits, including waste recycling.