A bibliometric analysis of the hydrogen production from dark fermentation

Hydrogen energy plays an important role in solving the environmental problems caused by the fuel crisis and greenhouse gas emissions. However, hydrogen application on an industrial scale still requires technological advances, especially in choosing the best technological route for the recovery of renewable and cost-effective hydrogen. Therefore, this bibliometric review evaluated the research progress, trends, updates, and hotspots on hydrogen production from dark fermentation. The Web of Science© database was used to select the documents from 2000 to 2021, and the VOSviewer© and Bibliometrix softwares were used to carry out the bibliometric investigation. The results demonstrated that 3071 documents (2755 articles and 316 reviews) studied the hydrogen production from dark fermentation over the last 21 years. The number of publications exponentially increased in the last five years, which can be associated with the demand for new technologies to produce clean energy sources and decrease the environmental impacts caused by petroleum-based fuel. Keyword analysis revealed that the studies focused on the operational parameters, process optimization, pretreatment, and microbial community, aiming to increase the hydrogen yield during dark fermentation. Finally, this comprehensive review provides future directions for applying dark fermentation to produce hydrogen as a sustainable and renewable fuel in a biorefiney concept.