Intensification of methane production from waste frying oil in a biogas-lift bioreactor

Abstract

Biogas upgrading from anaerobic digestion of waste frying oils (WFO) was accessed in this study. For that, two bioreactors (Rb-biogas-lift bioreactor with gas and liquid recirculation, Rc-control reactor with liquid recirculation) were fed three times per week, with a mixture of WFO, glycerol and volatile fatty acids (VFA). Rb produced 1.4 times more biogas with higher methane content (79%) than Rc (67%). Higher relative abundance of hydrogenotrophic methanogens (34%e39%) was observed in Rb, when compared to Rc (16%e21%). The relative abundance of Sprochaetia class, which includes some homoacetogens/ syntrophic acetate oxidizing genera, was also higher in Rb. This work shows that biogas recirculation applied in the biogas-lift bioreactor facilitated WFO degradation, most probably due to the selective enrichment of hydrogenotrophic methanogens. Recirculation of CO 2 present in the biogas and reverse homoacetogenesis (i.e. syntrophic acetate oxidation) seem to be the main factors involved in the stimulation of hydrogenotrophic methanogenesis.

Principles, Advances, and Perspectives of Anaerobic Digestion of Lipids

“…This improvement resulted from the enrichment of hydrogenotrophic methanogens. Biogas recirculation thus appears as a promising strategy to enhance biomethane production from lipids …”

“…Biogas recirculation thus appears as a promising strategy to enhance biomethane production from lipids. 180 Despite of all the achievements, the basic issue of LCFA inhibition and palmitate accumulation are still not clearly understood, and their comprehension might boost process performance. This could allow true high-rate (<24 h) digestion, larger energy gains (even at low, psychrophilic, temperatures), and ultimately lead to further implementation of resource recovery from lipids in wastewater.…”

Recent progress towards in-situ biogas upgrading technologies

“…This results in the dominance of the HM pathway, but it will lead to acetate accumulation, which ultimately will also inhibit the hydrogenotrophic methanogens. In some situations (for example, high ammonia, high temperature), syntrophic acetate oxidizers may become the dominant acetate-utilizers, oxidizing acetate to CO 2 and H 2 , which is further consumed by HM (Duarte et al, 2021;Dyksma et al, 2020). Moreover, the addition of H 2 directly to AD also switches the methanogenic metabolic pathway towards the HM pathway (Table 1).…”

Application of biogas recirculation in anaerobic granular sludge system for multifunctional sewage sludge management with high efficacy energy recovery

“…The increased CH4 production rate and shortened lag-phase duration via biogas recirculation could be attributable to various aspects, such as the promoted contact and interaction between substrates and microorganisms [16], and the increased buffering capacity in the AD system, especially during the hydrolysis stage due to enhanced dissolution of CO2. Besides the functions of mixing and enhanced contact between the microorganisms and substrates induced by biogas recirculation, CO2containing biogas recirculation may be responsible for the enrichment of hydrogenotrophic methanogens and their enhanced activities [18], [32], resulting in better AD performance of biogas-R1 and -R2. Table 1.…”