Sustainable Biohydrogen Production from Animal Manure: Review into Processes Optimization, Pretreatment Strategies, and Feedstocks Evaluation

Abstract

Transforming animal manure from an environmental liability into a renewable biohydrogen resource represents a promising strategy for simultaneously addressing waste management and clean energy production. A narrative comparative review was conducted based on the critical synthesis of 130 peer-reviewed publications. Comparative evaluation highlighted integrating Dark Fermentation (DF) and Photo Fermentation (PF) effectively exploits their complementary metabolic pathways, resulting in more efficient substrate utilization and enhanced biohydrogen recovery than either process alone. The review further demonstrated that combining pretreatment, operational optimization, and co-digestion consistently improved substrate accessibility, microbial activity, and overall fermentation performance. This combined approach enhances substrate conversion, supports microbial activity, and improves overall fermentation performance. Across diverse feedstocks including cow, pig, chicken, buffalo, and horse manure, reported biohydrogen yields ranged from 15.5–275.6 mL H2/g-VS, while production rates reached up to 1383 mL H2/L/day. The observed variability reflected differences in feedstock characteristics, pretreatment strategies, fermentation pathways, and operating conditions. Despite substantial technological advances, bridging the gap between laboratory findings and industrial implementation remains the principal challenge. Future research should therefore prioritize pilot-scale validation, integrated reactor engineering, techno-economic analysis, and life cycle assessment to accelerate commercial deployment.