Impact of Food Waste-Derived Compost with Varying Biochar Contents on Soil Carbon Dioxide (CO₂) Emissions

Rising atmospheric carbon dioxide (CO₂) levels contribute significantly to global warming, with agricultural soils acting as both major sources and potential sinks for greenhouse gases (GHG). This study investigated the impact of food waste-derived compost amended with varying concentrations of coconut husk biochar on CO₂ emissions from highly weathered tropical soil. Biochar was produced via pyrolysis at 550 – 620°C and co-composted with domestic organic waste (cassava, plantain, and pineapple peels, and poultry manure) at ratios of 0%, 2%, 5%, and 10%. Six treatments, including an absolute control and inorganic NPK fertilizer, were applied to soil containers and incubated for 58 days. CO₂ emissions were quantified using sodium hydroxide (NaOH) trapping followed by hydrochloric acid (HCl) titration at intervals ranging from day 0 to day 58. Results indicated a significant reduction in emissions across all treatments after the initial incubation day. The Compost + 10% Biochar treatment consistently demonstrated the lowest CO₂ emissions (0.88 mg CO₂/day/kg on day 0), significantly outperforming the control (1.21 mg CO₂/day/kg), inorganic fertilizer, and lower biochar concentrations. By day 58, emissions across all treatments approached zero. The study concludes that amending food waste compost with 10% coconut husk biochar effectively suppresses soil CO₂ fluxes, acting as a carbon sink while enhancing soil fertility. This integrated organic management strategy offers a sustainable, climate-smart solution for reducing greenhouse gas emissions and promoting soil health in tropical agricultural systems.