Synthesis evaluation on thermophilic anaerobic co-digestion of tomato plant residue with cattle manure and food waste

Abstract

Anaerobic digestion (AD) is an effective method for treating organic waste. However, the performance of anaerobic reactors needs to be improved and comprehensively analyzed. This study proposed a ternary co-feedstock strategy for thermophilic anaerobic co-digestion of tomato plant residue, cattle manure, and food waste. The effects of changing the feedstock composition, feedstock-to-inoculum ratio, and total solids (TS) content were investigated. Among the tested mixtures, a ternary mixture of 60% tomato plant residue, 20% cattle manure, and 20% food waste with a feedstock-to-inoculum ratio of 0.7 gave the highest cumulative biogas (3.230 L), methane yield (2.575 L), methane content (79.71%), co-digestion performance index (1.65) and volatile solids (VS) removal rate (60.59%). Changing the feedstocks compositions caused changes in the specific biogas yield and specific methane yield. In tests with TS contents of 5%, 10%, 15%, and 20%, a higher TS content increased biogas and methane production because of increases in the amount of the biodegradable fraction in the reactor. However, there was a risk of volatile fatty acid overloading and a decrease in the VS removal rate because of inefficient decomposition of the high total solids content by microbes in the inoculum.