Improving slaughterhouse byproducts utilization via anaerobic digestion, composting, and rendering

A large number of high-strength byproducts/wastes are discharged from slaughterhouses of meat industry in China and could pose serious environment pollution if without proper treatments. These wastes are rich in protein and lipid, and could potentially be utilized for effective recovery of energy and nutrients. In this study, three treatment scenarios of slaughterhouse wastes, namely anaerobic digestion (AD), composting, and rendering, were firstly investigated in China, and the greenhouse gas (GHG) emissions were calculated and compared. The results indicated that 23.1 Tg of slaughterhouse byproduct (SBP) and 679.7 Mm3 of wastewaters were estimated to discharge in 2020, which can potentially produce 2743 Mm3 of biomethane in AD, 316 Gg of nitrogen and 660 Gg of phosphorus nutrients in composting, or 5.4 Tg of rendering products in rendering. AD of SBP resulted in high GHG reductions (approximately 17.88 Tg of CO2-eq). The net energy produced from a typical pig slaughterhouse through treating SBP by the AD system was also estimated to be 194.7 GJ/d and GHG reduction was 100.3 Mg of CO2-eq/d. Technical challenges (include digester inhibition, odor emissions, and biosafety) were also summarized and discussed for practicing these technologies. Therefore, integrating the bioenergy/byproducts production to animal processing can potentially enhance the environmental sustainability of meat industry in China in the future.