Electrofuels: The Best Way to Turn Sunlight to Energy?
Electrofuels are made with energy from the sun and renewable inorganic feedstocks such as carbon dioxide and water in processes facilitated by nonphotosynthetic microorganisms or Earth-abundant metal catalysts.
“The electrofuels concept is an effort to decouple the production of liquid fuels from fossil fuels and land use, which is starting to constrain our daily lives,” said Gregory Stephanopoulos, a chemical engineering professor at Massachusetts Institute of Technology and leader of the conference’s organizing committee. _CEN
Bypassing photosynthesis allows engineers to devise alternative means to create chemical energy out of sunlight, at higher efficiencies than photosynthesis might allow. The image above portrays both chemical and biological catalysts being energised by sunlight to facilitate the synthesis of multiple fuels and chemicals. The use of entire biological micro-organisms which have been gene-engineered to use more efficient, non-photosynthetic pathways for synthetic production of high value chemicals and fuels, is one likely approach.
“The name of the game for electrofuels is to find more efficient ways to capture solar radiation in a form that’s usable for transportation,” commented Eric J. Toone, a chemistry professor at Duke University and deputy director of ARPA-E. The agency was created in 2009 with funding from the American Recovery & Reinvestment Act to boost development and commercialization of technologies that reduce U.S. dependence on foreign energy sources.And this is just the beginning. We cannot expect accomplished bio-revolutionaries such as Craig Venter, to reveal all the details of their latest projects. Nor can we expect rapid up-and-comers such as Jay Keasling to openly discuss everything on his mind.
“When looking at the amount of solar energy that is captured by a plant and the net amount of that energy it can harness, the value is on the order of 0.1 to 0.2%,” Toone said. “On the other hand, we know we can capture and convert solar energy to electricity at higher efficiency, on the order of 20% for current silicon photovoltaic cells. In the electrofuels approach, we’ve tried to bring together the best of both worlds, to develop catalytic systems capable of highly efficient energy assimilation from inorganic molecules for the direct production of fuels.”
...Stephanopoulos’ group at MIT has an electrofuels project under way that taps two customized microbes: One produces acetate from waste CO2 and H2 from sunlight-driven water electrolysis and the second microbe converts the acetate into a triglyceride that can be processed into a fatty acid methyl ester, which is the primary component of biodiesel.
Reporting on another technology, microbiologist Derek R. Lovley of the University of Massachusetts, Amherst, described a lab-scale electromicrobiology approach to electrofuels that takes advantage of some microbes’ ability to make electrical contacts with materials. His team is growing Geobacter or Clostridium bacteria on iron(III) oxide films on carbon electrodes. The microbes consume electrons released from the electrode as their energy source and metabolize CO2. Differently engineered bacteria can produce compounds such as acetic acid or butanol. _CEN
The sun has always been an enormous influence on human civilisations and cultures. It is likely that as soon as humans discover the best ways to utilise the energies of the sun -- and to copy the physical processes that drive the sun in labs -- a new revolution in human existence will be incited.