Cellulose decomposition and larval biomass production from the co-digestion of dairy manure and chicken manure by mini-livestock (Hermetia illucens L.).

World trends toward the modern dairies intensification on large production units cause massive animal manure production and accumulation. Improper handling of manure produced by industrial farm operation greatly deteriorates the major environmental media including air, water and soil. The black soldier fly utilizes organic waste and converts it into larvae biomass to be used as livestock feed and into residues to be used as bio-fertilizer. However, due to the high ratio of cellulose, hemicellulose and lignin in dairy manure, this conversion is difficult. Therefore, dairy manure treated with chicken manure was digested by Hermetia illucens. In this paper, we found that the co-digestion process significantly enhanced the larval production, waste mass reduction, rate of larvae conversion, feed conversion ratio, nutrient reduction and fibers utilization. Whereas 40% dairy manure and 60% chicken manure group show better results than other manure mixtures and had a significantly increased the cellulose consumption by 61.19%, hemicellulose consumption by 53.22% and lignin consumption by 42.23% compared with 49.89%, 49.77% and 31.95%, respectively, in the dairy-only manure group. Finally, scanning electron microscopy was used to analyze the structural changes of dairy manure, chicken manure and their co-digestion mixtures. The scan electron microscopy showed the deterioration in the structure of dairy and chicken manure fibers by Hermetia illucens. Moreover, the carbon-nitrogen ratio was decreased in all end products of post vermicomposting. The results suggest that the co-digestion of 40% dairy manure with 60% chicken manure is an appropriate proportion for dairy manure management with the black soldier fly.