Effect of hydrothermal pretreatment on two-stage anaerobic digestion of food waste and Enteromorpha: Digestion performance, bioenergy efficiency, and microbial community dynamics

Abstract

The effects of hydrothermal pretreatment (HTP) on the performance, bioenergy efficiency, and microbial community dynamics of two-stage anaerobic digestion (AD) of food waste (FW) and Enteromorpha were analyzed. The results showed that hydrogen production and total volatile fatty acids (VFAs) concentration in the dark fermentation (DF) stage and cumulative biomethane yield in the methanogenic stage exhibited an increasing trend in response to increasing HTP temperature. The highest hydrogen and biomethane yields of 62.7 ± 0.3 and 590.6 ± 8.0 mL·gVS−1 were obtained at HTP temperature of 140 °C, which were 242.6% and 11.8% higher than those in two-stage AD with untreated substrates (designated as RTCK), respectively. Simultaneously, bioenergy generation yield (BGY) of 21.18 ± 0.44–24.21 ± 0.32 kJ·gVS−1 in two-stage AD achieved bioenergy conversion efficiency (BCE) of 71.69–80.37% and process energy efficiency (PEE) of 22.31–39.01%, which showed 14.27–16.91% and 24.83–31.15% improvement compared to one-stage AD, respectively. HTP significantly altered the bacterial communities, resulting in the enrichment of butyric- and acetic-type fermentation bacteria and the inhibition of propionate-type fermentation bacteria. This study demonstrated that HTP could improve the performance and achieve a higher BGY in two-stage AD.