Reduction of Odors and Greenhouse Gases from Composting Processes Using Biochar from Locally Available Bio-resources

Conducted as part of the Waste to Fuels Technology (WTFT) Partnership 2021–2023 Biennium, this report investigates the potential for locally available biochar to reduce greenhouse gas and odor emissions from composting systems. The study evaluated 12 commercial and industrial biochar samples, including materials derived from forest residuals, to determine their suitability for adsorbing ammonia (NH₃), methane (CH₄), and hydrogen sulfide (H₂S).

Researchers characterized biochar physical and chemical properties—including surface area, pore distribution, elemental composition, pH, ash content, and functional groups—and measured gas adsorption capacity using laboratory breakthrough curve experiments. Based on these findings, an engineered acidic biochar was produced and combined with commercial biochar to create a “biochar cocktail” for bench-scale composting trials.

Results demonstrated that acidic biochar effectively reduced ammonia emissions, high surface area biochar enhanced methane adsorption, and basic, high-ash biochar improved hydrogen sulfide adsorption. Composting reactor experiments confirmed that biochar filters significantly reduced ammonia emissions and odors during active composting. Findings inform scalable strategies for integrating biochar into industrial composting to reduce emissions while supporting Washington’s organics management goals.