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 (NH3) and hydrogen sulfide (H2S) during tomato straw composting. Compared with the control, rice husk biochar, acid-modified rice husk biochar, and a lignin-based resin reduced NH3 emissions by 32.84%, 54.23%, and 42.89%, respectively. However, their effects on H2S 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 NH3 while enhancing porous adsorption of H2S. 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 NH3 and H2S. 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.