Enhanced anaerobic digestion of post-hydrothermal liquefaction wastewater: Bio-methane production, carbon distribution and microbial metabolism

Hydrothermal liquefaction (HTL) isa cost-effective and environment-friendly technology for using biomass to produce bio-crude oil. The critical challenge of HTL is its complicated aqueous product containing high concentrations of or-ganics and diverse toxicants. This paper reports the continuous anaerobic digestion of raw and zeolite-adsorbed Chlo-rella HTL wastewater using up-flow anaerobic sludge bed reactors. The bio-methane production capacity, total carbon distribution and microbial response were investigated. The anaerobic process was severely suppressed when more than 20% raw wastewater was fed; while it showed essentially improved performance till 60% pre-treated wastewater was added. Produced methane contained 17.3% of the total carbon in feedstock, which was comparable with the value (16.7%) when 25% of raw wastewater was added. The metagenomic analysis revealed distinct microbial community structures in different stages and feedstock shifts. The abundance of functional genes was consistent with anaerobic digester performance.

Automated summary

This paper investigates the continuous anaerobic digestion of hydrothermal liquefaction (HTL) wastewater and finds that the performance of the anaerobic process is significantly improved when pre-treated wastewater is added, and the produced methane contains 17.3% of the total carbon in the feedstock.