PRJNA575652
Combined acetate, lactate and biogas production from food waste or sewage sludge using different inoculum sources
The effect of inoculum and substrate on acetate production was evaluated in semi-continuous experimens. Efficicency of hydrolysis, acidogenesi, acetogenes and methanogenese was evaluated and the microbial community in the different processes was studied and correlated to the performance. Sewage sludge and food waste was applied and while sewage sludge lead to mixed acid fermentation and low acid yield the food waste prcesses resulted in high fractions of acetate and lactate. Also the inoculum affected the process where inoculum from wastewater treatment plant (WWTP) fed with sewage sludge resulted in maintained methane production despite low hydrolic retention time (HRT; 3 days) and high organic loading rate (OLR; 23.7 kg VS/m3 d). For food waste (OLR 13.5 kg VS/m3 d and HRT 10 days) the process inoculated from WWTP produced high levels of lactate (30 g/L) and acetate (10 g/L) while the process inoculated from a co-digestion plant had higher acetate levels (25 g/L) and lower lactate (15 g/L). The microbial communities developed during acid production consisted of the major genera Lactobacillus (92-100%) when fed food waste and Roseburia (44-45 %) and Fastidiosipila (16-36 %) when fed sewage sludge waste. Application of the hyrolysates to a biogas production system resulted in higher, but non-significant increase of bio-methane production compared to directly using the substrate for biogas production (5-20 % increase).