Anaerobic co-digestion of kitchen waste and animal manure: a review of operating parameters, inhibiting factors, and pretreatment with their impact on process performance

The aberrant use of fossil fuels and greenhouse gases impact on the environment made researchers leverage efforts into renewable energy generation from organic resources such as wastes. Researchers and scientists searched and studied for years so as to find an alternative fuel sources. Recent studies have supported anaerobic digestion (AD) as alternative and efficient technology that combines biofuel production and sustainable waste management. Laboratory-scale and field studies have proved kitchen waste and animal manure as feasible sources of substrate for methane generation. The effects of parameters and pretreatment affecting the co-digestion of kitchen waste and animal manure in different scientific databases within 2001–2020 were searched, and related information was obtained. Animal manure has 72–93% volatile solid, low total solid (TS) content which ranges between 5 and 9%, and high water content, while kitchen waste contains 85–96% volatile solid (VS) and high amount of water content. These characteristic properties indicate that these wastes can be efficient sources for biofuel/biogas production. This article constitutes a comprehensive review that compares and summarizes studies concerning anaerobic co-digestion of kitchen waste and animal manure, factors and inhibitors that affect the process as well as empirical studies of pretreatment techniques for co-digestion of kitchen waste and animal manure.