Jan 1, 2023 · Piggery slurry was efficient treated in ectopic fermentation bed system composting (30 kg/m 3 /d), NO 3 −-N improved 58.3 times and NH 4 +-N reduced by 0.2mg/g, and enriched the microbe abundance and diversity [84], [85], [86]. The tunnel kiln composting system is a fully enclosed fermentation system with a mutually independent tunnel structure.