Mini review: hydrogen and ethanol co-production from waste materials via microbial fermentation

Abstract

The simultaneous production of hydrogen and ethanol by microorganisms from waste materials in a bioreactor system would establish cost-effective and time-saving biofuel production. This review aims to present the current status of fermentation processes producing hydrogen accompanied by ethanol as a co-product. We outlined the microbes used and their fundamental pathways for hydrogen and ethanol fermentation. Moreover, we discussed the exploitation of renewable and sustainable waste materials as promising feedstock and the limitations encountered. The low substrate bioconversion rate in hydrogen and ethanol co-production is regarded as the primary constraint towards the development of large scale applications. Thus, microbes with an enhanced capability have been generated via genetic manipulation to diminish the inefficiency of substrate consumption. In this review, other potential approaches to improve the performance of co-production through fermentation were also elaborated. This review will be a useful guide for the future development of hydrogen and ethanol co-production using waste materials.

Exploring untapped energy potential of urban solid waste

“…Apart from this, palm oil mill effluent which is one of the biggest problems in Malaysia (Embrandiri et al 2015) has energy potential of 20.23 Mtoe (Ng et al 2012). Likewise, biomass energy potential of Sweden from municipal waste is 56 PJ/yr, whereas from agricultural solid waste it is 237 PJ/yr (Wiesenthal and Mourelatou 2006;Skovgaard et al 2008). The above section highlights that there is a tremendous potential of energy generation stored in waste.…”

“…Likewise, biohydrogen is also being produced by decomposing carbohydrate-rich waste material through this simple technology. Biohydrogen could be produced either by dark fermentation or through photo-fermentation (Ntaikou et al 2010;Chaubey et al 2013;Soo et al 2015). At the end of the fermentation process, alcohol solvents and organic acids are produced apart from hydrogen which can also be commercially utilized instead of being discharged as waste.…”

“…Till date, there are no proper strategies for improving substrate conversion efficiency of the process. Hence, regulating fermentation parameters and genetic modification of the microbes could represent a promising process for conversion of waste into energy (Huang et al 2010;Soo et al 2015). Wang et al (2012) examined the LCA for environmental sustainability of process so as to provide a base for decision makers to recognize the main drivers of environmental profiles.…”

Simultaneous Hydrogen and Ethanol Production from Crude Glycerol by a Microbial Consortium Using Fed-Batch Fermentation

“…Simultaneous production of hydrogen and ethanol from waste materials has the potential for the development of a more cost-effective biofuel generation process. Their co-production is more beneficial in terms of cost and time savings compared to fermentation focusing on either hydrogen or ethanol production alone [4,5].…”

“…However, very little research has been conducted with the aim of optimizing the simultaneous production of hydrogen and ethanol from CG fermentation at the same time. Mostly, studies were conducted with pure culture [5,18,19] and engineered strains [20,21]. Recently, two studies reported the production of hydrogen and ethanol from CG by mixed culture fermentation [22,23].…”