Influence of type of organic solid waste and process temperature on lactate-driven hydrogen production and microbial community by self-fermentation

Organic solid waste (OSW), depending on its origin, shows differences in the carbohydrates, lipid, and protein content, influencing its potential for valorization. This study aimed to evaluate the influence of three types of OSW (restaurant food waste (RFW), market waste (MW), and the organic fraction of municipal solid waste (OFMSW)) and temperature (37 and 55°C) on hydrogen production, metabolites production, and microbial community composition. The native microbiota of each OSW served as inoculum. Results confirmed that the type of feedstock significantly influenced lactate-based hydrogen production, which was temperature-dependent. Mesophilic self-fermentation of OFMSW yielded the highest hydrogen production, reaching 257 mL H 2 /L, 23% higher than the obtained at thermophilic conditions and 71% higher than that obtained from MW at mesophilic conditions. Hydrogen production of OFMSW at both 37°C and 55°C and MW at 37°C was correlated with the butyric acid production and the presence of the Clostridium genus. In contrast, RFW at 37 and 55 °C was associated with lactic acid production and a higher abundance of Lactobacillus and Bacillus , respectively. Results demonstrated that OFMSW can be directly converted to hydrogen, while RFW produces lactic acid, which could serve as a precursor for lactate-based hydrogen production in a two-stage process. • Self-fermentation of OFMSW produced hydrogen, regardless of temperature. • Self-fermentation of RFW resulted in lactic acid production at 37 and 55 °C. • Temperature influenced the microbial community composition. • Clostridium lead hydrogen and Lactobacillus / Bacillus contributed to lactic acid production.