Mitigation of ammonia and hydrogen sulfide emissions from biochar-treated swine manure after application to cropland soil

Authors: O'BRIEN, SAMUEL - Iowa State University; Koziel, Jacek; RAMIREZ, BRETT - Iowa State University; Ortiz, Anna

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2025
Publication Date: 2/12/2026
Citation: O'Brien, S.C., Koziel, J.A., Ramirez, B.C., Ortiz, A.C. 2026. Mitigation of ammonia and hydrogen sulfide emissions from biochar-treated swine manure after application to cropland soil. Applied Engineering in Agriculture. 42(1):135-145. https://doi.org/10.13031/aea.16394.
DOI: https://doi.org/10.13031/aea.16394

Interpretive Summary: Managing air quality is essential for sustainable livestock and crop agriculture. Gaseous emissions from land-applied manure are challenging to mitigate. Swine manure improves soil structure, provides nutrients to the soil, and promotes beneficial microbial growth, all while being locally sourced. In this research, a team of scientists from ARS at Bushland, Texas, and Iowa State University found that it is possible to reduce gas emissions by applying biochar to the surface of manure immediately prior to land application. As little as 0.25-inch-thick layer of biochar reduced up to 90% of ammonia and 61% of hydrogen sulfide, respectively. Biochar has a potential to address environmental issues associated with gaseous emissions while promoting the sustainability of manure application as a fertilizer. Additional testing is recommended to determine optimal biochar types and effective doses.

Technical Abstract: Air quality management is essential for sustainable livestock production. Manure generates odorous and greenhouse gases (GHGs) emissions during storage and cropland application. Emissions of ammonia (NH3) during manure application to soil represent a loss of nitrogen and decrease the value of manure. Biochar (BC) can mitigate emissions during manure storage. In this research, we hypothesized that BC-treated manure generates less emissions after post-storage application to cropland soil. This study tested the effect of BC thickness (dose) and manure treatment timing on gaseous emissions in controlled lab-scale experiments. NH3 and hydrogen sulfide (H2S) emissions from cropland soil amended with BC-treated manure were reduced. Overall, the average percent reduction in the first 6 h / 24 h was 89.9 / 89.7% and 59.6 / 60.8% for NH3 and H2S emissions, respectively, when manure was treated with BC immediately prior to application to the soil. When manure was treated with BC during storage, emissions were reduced 20.7 / 21.8% and 12.2 / 13.5% for NH3 and H2S, respectively. The percent reductions in NH3 and H2S for 13- and 6.5-mm BC application thickness were not different from each other, but the 2.5 mm application thickness treatment was not as effective at reducing gas emissions. The effects of BC application on methane (CH4), carbon dioxide (CO2), and odor were inconclusive. Observational data indicated a possible mitigation trend to odor, especially for the BC treatment added immediately prior to application to soil, but more repeated trials are needed. Scaling up technoeconomic analysis showed that less than 6 m3 of BC would be needed to treat over a 900 m2 surface of stored manure in a typical 1,200-head swine barn with a uniform 6.5 mm thick BC layer. Subsequent cropland application of such BC-treated manure would result in 0.1 m3/ha BC addition to soil in a typical corn-soybean crop rotation system. This research shows that BC has the potential to mitigate gaseous emissions while promoting nutrient cycling and the sustainability of livestock waste as a fertilizer.