Opportunities toward hydrogen production biotechnologies
Graphical abstract
Introduction
In 2003, President George W. Bush announced a major R&D initiative toward adoption of hydrogen fuel for powering vehicles and generating electricity (CNN.com/inside politics, 2/6/03; https://georgewbush-whitehouse.archives.gov/infocus/technology/economic_policy200404/chap2.html). Unfortunately, the scientific, technological, and economic hurdles proved daunting. One major limitation, still in force, is the paucity of cost-effective and sustainable technologies for hydrogen production. Nascent biological technologies apparently provided attractive opportunities, and many development projects were funded. However, results were disappointing. This overview is offered to briefly assess past efforts toward cost-effective biohydrogen production, but, more importantly, to use fundamental scientific and engineering insights to suggest an effective path forward.
In the U.S., most of the hydrogen used industrially is produced from natural gas (afdc.energy.gov/fuels/hydrogen_production.html). While this technology releases large quantities of CO2, it also sets a high bar for biohydrogen economic performance since current wholesale natural gas prices are about 20% of wholesale gasoline prices based on energy content. Consequently, initial large scale implementation of biohydrogen technologies will most likely require specific local incentives as well as exceptional metabolic and process engineering. This overview will concentrate on two such opportunities: 1) geographically distributed conversion of crop wastes (hydrolyzed cellulosic biomass) into hydrogen for local production of ammonia fertilizer; thereby lowering agricultural carbon release footprints; and 2) solar production and storage of hydrogen (and oxygen) for centralized electricity generation to mitigate renewable energy intermittencies.
The basic metabolic systems are diagrammed in Figure 1. Both approaches offer relatively direct and potentially efficient utilization of reducing equivalents, a characteristic essential for cost-effective hydrogen production.
Section snippets
Learning from previous biohydrogen R&D
This article is not intended as a thorough review of previous biohydrogen process development, but a brief chronological summary helps to define challenges and opportunities.
Exploiting further [FeFe]-hydrogenase mutagenesis
Functional comparison of over 300 singly or doubly mutated CpIs [10••] failed to reveal any correlation between the effects of electron transfer pathway mutations on activity versus effects on oxygen tolerance. This observation suggests a strong probability for discovering more fully oxygen tolerant mutants with high activities. The new production and evaluation procedures can now be implemented for screening thousands of mutants in 96-well plate formats. To reduce electrical impedance, random
Conclusions
Rejuvenated expectations toward economical, large scale biohydrogen technologies are now supported by: a) opportunities to reinvent photosynthetic systems, b) highly integrated process designs, c) improved host organisms, and d) advances in [FeFe]-hydrogenase functionality. While development and deployment decisions must still recognize that Permian Basin natural gas is currently a liability (i.e. methane derived H2 is very inexpensive); global concerns are paramount. We absolutely must address
Conflict of interest statement
Nothing declared.
References and recommended reading
Papers of particular interest, published within the period of review, have been highlighted as:
• of special interest
•• of outstanding interest
Acknowledgements
The author would like to thank Professor Chris Walsh and Dr Richard Sassoon for encouragement and helpful discussions.
This research did not receive any specific grant from funding agencies in the public, commercial, or non-for-profit sectors.
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