Thermophilic biohydrogen production: how far are we?

Abstract

Apart from being applied as an energy carrier, hydrogen is in increasing demand as a commodity. Currently, the majority of hydrogen (H2) is produced from fossil fuels, but from an environmental perspective, sustainable H2 production should be considered. One of the possible ways of hydrogen production is through fermentation, in particular, at elevated temperature, i.e. thermophilic biohydrogen production. This short review recapitulates the current status in thermophilic biohydrogen production through fermentation of commercially viable substrates produced from readily available renewable resources, such as agricultural residues. The route to commercially viable biohydrogen production is a multidisciplinary enterprise. Microbiological studies have pointed out certain desirable physiological characteristics in H2-producing microorganisms. More process-oriented research has identified best applicable reactor types and cultivation conditions. Techno-economic and life cycle analyses have identified key process bottlenecks with respect to economic feasibility and its environmental impact. The review has further identified current limitations and gaps in the knowledge, and also deliberates directions for future research and development of thermophilic biohydrogen production.

Optimization of key factors affecting hydrogen production from sugarcane bagasse by thermophilic anaerobic pure culture

“…Moreover, the HPR values increased over time in the initial stage of fermentation and decreased after the maximum HPR of 0.52 L/L · h obtained at the point of 4 h fermentation. Most thermophiles are able to hydrolyze various polysaccharides and ferment the released hexoses and pentoses to H 2 with yields close to the theoretical maximum of 4 mol H 2 /mol hexose [6]. Nielet al [27] reported a hydrogen yield of 3.33 mol/mol hexose using either Caldicellulosiruptor saccharolyticus on sucrose (70°C) or Thermotogaelfii on glucose (65°C), and similar yields were achieved by Mars et al using hydrolyzed potato steam peels as the substrate [28].…”

“…Various types of microorganisms can play a role in hydrogen formation by dark fermentation. However, thermophiles are energetically more favorable for hydrogen production, generating higher H 2 yields and fewer undesirable by-products than mesophiles [6]. Moreover, strictly anaerobic thermophilic conditions seem to restrict contamination by other microorganisms [7].…”

Thermococcus kodakarensis : the key to affordable biohydrogen production

“…To enhance the economy of the microbial dark fermentation, it is necessary to improve the sugar-to-H 2 yield. Current sugar-to-H 2 yields by microbial dark fermentation vary from less than 1 to almost 4 moles of H 2 /mole of hexose consumed [13,14,43,48,49], the latter corresponding to about a third of the theoretical yield of 12 moles. The production of 4 H 2 /hexose is regarded as the upper limit ("Thauer limit", [51]), of standard metabolisms, and increased yields require further oxidation of substrates to CO 2 .…”

“…In addition, H 2 can be produced industrially via various methods such as electrolysis or thermolysis [10][11][12][13][14]. Since its discovery, H 2 has become an important chemical commodity.…”

“…Microbial dark fermentation Current sugar-to-H 2 yields by microbial dark fermentation vary from less than 1 to almost 4 mole of H 2 /mole of hexose consumed ( Table 1.1) [13,14,43,48,49]. The differences in yield are mainly due to the types and relative proportions of the products generated by fermentation.…”