Microbial electrochemical treatment of biorefinery black liquor and resource recovery

Biorefineries valorize waste biomass to biofuels and bioproducts, but the associated wastewater treatment is costly and energy-intensive. This study demonstrates that not only the recalcitrant black liquor generated from biorefineries can be treated using a microbial electrochemical process, but also value-added materials including lignin, chemicals, and H₂ can be separated to enable resource recovery. A lab scale microbial biomass recovery cell (MBRC) was developed to treat the actual black liquor from the deacetylation and mechanical refining (DMR) process, and the results show that 60.1-73.8% of organics, 52.0-54.6% of salts, and 30.8-49.5% of lignin were removed using different operational modes. Moreover, by utilizing the unique pH gradient generated between the different reactor chambers, tailored recoveries of lignin, chemicals, and H₂ were realized for the first time. The recoveries of lignin and salts were up to 61.2 ± 2.7% and 92.2 ± 1.6%, respectively. Ion transfer and organic transformation were further analyzed to understand the reaction mechanisms and improve the system performance.