Systematic literature review of the sustainability and environmental performance of dark fermentative biohydrogen production

This study provides a systematic literature review, reporting the environmental and sustainability assessment of dark fermentative biohydrogen production. Eight thousand eight hundred forty peer-reviewed articles were obtained from online databases; only 43 were considered for review in this study. Among the life cycle stages, the result outcomes for the life cycle inventory analysis are mostly reported in the literature, accounting for 23%; this is followed by the system boundary, functional unit and goal and scope of the study, comprising 20%, 15% and 9%, respectively. These studies' focus varied with further studies on the storage of biohydrogen (36%), followed by biohydrogen application (23%) and biohydrogen production accounted for only 9%, respectively. The reviewed studies were reported from secondary inventory datasets compared to primary inventory datasets. Several studies failed to formulate a clear study goal and scope, causing misrepresentation of the environmental outcomes. Based on this literature review, the sustainability assessment of biohydrogen production is still premature, requiring dedicated efforts to generate adequate inventory data for efficient sustainability assessment.