Anaerobic digestion of cornmeal – the effect of crude enzyme extract and co‐digestion with cow manure

Abstract

This study examined the effect of a crude enzyme extract, containing mainly starchdegrading enzymes, on cornmeal (Zea mays) hydrolysis. This was followed by an investigation of the effect of enzymatic treatment for the anaerobic digestion of this biomass. Cornmeal and cow manure were also co-digested, and both batch and semi-continuous experiments were performed. The enzymatic pretreatment of cornmeal resulted in a yield of 65 ± 5% reducing sugars, with 1:10 w/v (grams of dry substrate per mililiters of enzyme extract) enzyme load at 45 °C for 48 h. There was an 8% enhancement of methane production observed during the batch assays, both when cornmeal hydrolysate was digested and when enzymes were added directly to the digester. Synergetic effects were found when co-digesting cornmeal and cow manure, leading to higher methane yield (280 NmL gVS -1 ) than that (200 NmL gVS -1 ) calculated based on the methane potential of the individual substrates. Regarding long-term effects, the laboratory-scale semi-continuous experiments also demonstrated that the co-digestion of cornmeal and cow manure (1:1 volatile solid (VS) basis) led to a stable process reaching an organic loading rate of 3 g VS L day -1 and achieving a daily methane production of 1280.12 ± 99.4 NmL CH 4 /day. However, when cornmeal was investigated in monodigestion, and the enzyme extract was directly added during semi-continuous digestion of cornmeal, volatile fatty acid (VFA) accumulation was observed, leading to a decrease in pH, and no significant enhancement of the conversion into methane was observed.

Microbial Pretreatment of Chicken Feather and Its Co-digestion With Rice Husk and Green Grocery Waste for Enhanced Biogas Production

“…The TSs and VSs in all the substrates used in the experiments were determined according to National Renewable Energy Laboratory’s analytical procedures. The usual procedures were used to determine the sample’s TS and VS ( Pinheiro et al, 2021 ), and the analysis of each sample was performed in triplicate. The characteristics of the substrates are demonstrated in Table 1 .…”