Integrating Compost and Biochar for Improved Air Quality, Crop Yield, and Soil Health

This technical report examines how integrating biochar with composting can reduce air emissions from composting processes while improving crop productivity and soil health. Conducted under the Waste to Fuels Technology Partnership 2019–2021 Biennium, the work combines field and laboratory measurements of volatile organic compound (VOC) emissions with greenhouse and field trials evaluating soil amendment performance.

Experiments assessed whether adding biochar at the start of composting reduces odor-related VOC emissions, with laboratory results indicating that 10% biochar can reduce emissions of monoterpenes, dimethyl disulfide, and other compounds. The report also compares compost, biochar, co-compost (biochar added during composting), and compost plus biochar as soil amendments across multiple sites and crops in Washington, including basil, strawberries, and potatoes. Results show yield responses that vary by amendment type, crop, and soil, with notable gains in some trials and limited effects in others. Soil physical and chemical properties often improved, depending on native soil conditions and application rate.