Impact of zeolite amendment on composting of food waste digestate

Food waste digestate (FWD) is an organic waste characterized by high NH₄⁺-N content and its composting is challenging due to the higher NH₃ emission and nitrogen loss. In the present study, FWD was co-composted with sawdust and mature compost, and zeolite was used as a physical additive for nitrogen conservation. The results demonstrated that amending 5% and 10% zeolite reduced the NH₃ emission to 1.8% and 1.6%, respectively, compared to 2.5% in the control without any zeolite. Overall, the zeolite amendment had a positive impact on nitrogen conservation as the nitrogen loss could be mitigated by 34–39% using 5–10% dosages. Besides, the zeolite addition showed considerable improvement in the FWD decomposition as the degradation rate was increased by 30–32% resulting in a carbon loss of 27–29%. Furthermore, the phytotoxic nature of FWD could be diminished by zeolite amendment which reduced the NH₄⁺-N contents to a permissible limit (≤500 mg/kg dm) and increased the seed germination index to > 80% in 14 days of co-composting.