Biodegradation kinetics of ammonium enriched food waste digestate compost with biochar amendment

High concentration of NH₄⁺-N in food waste digestate (FWD) produced from biological treatment of food waste is considered as a major threat on the composting process resulting in production of immature compost. Hence, a laboratory batch composting study was conducted to examine the feasibility of using biochar as a physical additive to ameliorate the inhibitory effect of NH₄⁺-N and to mitigate the nitrogen loss during FWD composting. FWD was co-composted with tobacco biochar at a dosage of 0%, 2.5%, 5% or 10% (dw) in bench-scale composters with a controlled aeration system. The addition of 10% biochar enhanced the degradation rate resulting in 44% higher carbon decomposition than the control. Besides, 10% biochar amendment reduced NH₃ and N loss by 58% and 5%, respectively and significantly reduced NH₄⁺-N content to HKORC limit of < 700 mg/kg dw within 5 days showing the beneficiary impact of biochar addition.