Short-chain fatty acids production from hydrothermal conversion wastewater (HTCWW): focusing on microbial community analysis.

Hydrothermal conversion (HTC) is a widely recognized method to produce biofuel and hydro-char from biomass. This study investigated the production of short-chain fatty acids (SCFAs) from HTC wastewater (HTCWW) through anaerobic fermentation (AF) and optimized the process conditions in both continuous stirred tank reactors (CSTR) and anaerobic sequencing batch reactors (ASBR). The highest SCFAs yield 0.382 g/g SCOD was achieved in ASBR when pH = 9.5 and 0.363 g/g SCOD in CSTR when pH = 9.5. Mass balance analysis suggested SCFAs were primarily derived from soluble proteins and soluble carbohydrates. Microbial communities varied under different conditions, with pH being the key factor. Firmicutes, Bacteroidetes, and Proteobacteria were dominant phyla, and Firmicutes were highly enriched at pH 9.5 (>70 %). Notably, Guggenheimella was the prevalent genus in the 9.5ASBR, exhibiting versatility in degrading various compounds to generate SCFAs, particularly acetate. This research presents a novel approach to converting HTCWW from WAS into value-added products.