Modified carbon-based additive can achieve mitigation of ammonia and hydrogen sulfide emissions simultaneously in composting

Malodorous gas emissions present a major constraint to the widespread adoption of composting technologies. In this study, a lab-scale simulated composting system was used to evaluate the effects of different carbonaceous additives on the emissions of ammonia (NH 3 ) and hydrogen sulfide (H 2 S) during tomato straw composting. Compared with the control, rice husk biochar, acid-modified rice husk biochar, and a lignin-based resin reduced NH 3 emissions by 32.84%, 54.23%, and 42.89%, respectively. However, their effects on H 2 S emissions varied: acid-modified rice husk biochar and lignin-based resin reduced emissions by 12.78% and 31.35% respectively, but pristine rice husk biochar instead increased them by 18.18%. Mechanistic analysis revealed that the acid-modified biochar utilized acidic surface functional groups to chemically immobilize NH 3 while enhancing porous adsorption of H 2 S. The lignin-based resin exhibited a synergistic effect, suppressing both gases through combined adsorption and microbial activity modulation, thereby emerging as the most effective additive for simultaneous reduction of NH 3 and H 2 S. This research provides theoretical basis for selecting efficient and environmentally benign deodorants in composting and offers a practical framework for their application in agricultural waste management.