Dual-stage pulse-feed operation enhanced methanation of lipidic waste during co-digestion using acclimatized consortia

Abstract

Methanation was improved during the dual-stage pulse-feed anaerobic co-digestion of extracted lipid (EL) from food waste leachate using acclimatized consortia by gradually increasing the organic loading rates (OLRs) in the subsequent phases. The utilization of major saturated and unsaturated long chain fatty acids (LCFAs) reached 78% and 98% in the acidogenic fermenters with consecutive organic loading, respectively. The acclimatized consortium induced the LCFA degradation and interconversion of short-medium chain fatty acids (SCFA–MCFAs) in the fermenters, even under highest OLR values. The highest methane yield (0.46 g g−1 VSinitial) was achieved in the third phase (61% EL loading of total injected volatile solid) with the complete utilization of LCFAs and SCFA–MCFAs in the digester. The assessment of the microbial community revealed that acidogenic Intestinimonas and Megasphaera, and acetogenic Levilinea were predominant in the fermenters due to their preeminent activities. The predominance of acetogenic Syntrophomonas (26%) indicated that it played a major role in β-oxidation, and its syntrophy with mixotrophic methanogens, such as Methanosarcina (93%), facilitated methanation through the complete degradation of EL in the digesters. The use of pulse-feed operation in dual-stage anaerobic co-digestion improved the methanation through complete utilization of EL under varied OLRs mediated by the acclimatized consortia.