The implication of continuous thermophilic composting for the resource recovery from slaughterhouse waste

This study implies the continuous thermophilic composting (CTC) in the context of sustainable management and resource recovery from slaughterhouse waste (SHW). Various temperature trials, including 35 °C, 45 °C, 55 °C, and 65 °C, were applied using a batch mode in-vessel composting system to determine its impact on the composting of SHW. It was observed that thermophilic temperature trials (55 °C and 65 °C) significantly enhanced the pH of the compost matrix, promoting both degradation and mineralization processes. The highest degree of OM degradation (56.59%) was recorded at 65 °C, followed by 55 °C (53.52%). Similarly, in comparison to the initial ash content (13.76%), the maximum ash content (54.19%) was observed at 65 °C after 40 days of incubation. Substantial variations were also observed for NH4+-N and NO3−-N concentration, where the highest NH4+-N (334.55 mg kg−1) and NO3−-N (157.63 mg kg−1) concentrations were observed at 65 °C, followed by 55 °C. Compost stability was achieved within 40 to 45 days in the trial incubated at 65 °C, and remained unchanged when the temperature was maintained at 25 °C for the last 10 days of experimentation. Therefore, compared to 55 °C, composting at 65 °C with uniform turning to ensure proper air supply can achieve compost stability in 40 to 45 days, with compost quality according to international compost quality guidelines. However, future research is required to explore the enlargement of the scale of CTC, microbial analysis in the final compost, nitrogen losses in the form of ammonia emissions and novel additives to reduce nitrogen losses and enhance the quality of SHW composting.