For millenniums, microbes have been a staunch technological ally. They have leavened our bread and cured our cheeses. Now, engineers are asking them to convert carbon dioxide into fuel and to build a new generation of batteries. Some of the smallest life forms with which we share the planet are helping us cope with the energy challenges of the 21st century.
Forget about the so-called hydrogen economy for a moment. The much-discussed plan to use hydrogen as a major power source has serious problems, such as how to deliver the fuel to consumers.
Bruce Logan at Penn State says methane could be a much more appealing candidate. Through the study of how microbes produce methane in swamps, bogs, and landfills, he and his colleagues believe they have found a perfect source for the gas.
They found certain microbes that use electricity to convert CO2 and water into methane. These hydrolysis cells convert electrical energy into energy stored in methane with 80 percent efficiency.
Technical details of this research appeared in the journal Environmental Science and Technology, and Professor Logan emphasized the potential environmental benefits in a separate statement. No extra carbon has to be added to make methane, he writes. When the gas is burned for fuel, it only lets off as much CO2 as originally went in, saving utilities from pumping more greenhouse gases into the environment. Furthermore, if the electricity used in the process comes from solar or wind power, the entire fuel cycle would not add any extra CO2 to the environment.
“The process does not sequester carbon, but it does turn carbon dioxide into fuel,” Logan explains. “If the methane is burned and carbon dioxide captured, then the process can be carbon neutral.”
At the Massachusetts Institute of Technology, Angela Belcher and colleagues are adopting viruses as engineering partners. With a little genetic tweaking, they have enabled what’s called an M13 virus to self-construct a wiring network for an improved lithium-ion battery. The technical details published in the April 2 online edition of Science described virus-produced batteries that MIT says “have the same energy capacity and power performance as state-of-the-art rechargeable batteries being considered to power plug-in hybrid cars.”
The MIT announcement explains that the viruses “first coat themselves with iron phosphate, then grab hold of carbon nanotubes to create a network of highly conducting material.” The batteries can’t be recharged as many times as regular lithium-ion cells. However, Dr. Belcher says that, as development progresses, “we expect them to be able to go much longer.”
The term “virus” often has a negative connotation. Yet they are part of the biology of our planet. The viruses used in this work are harmless to humans, according to the MIT announcement. As engineers face this century’s technical challenges, we can expect to see more knowledge from biology joining traditional, physical know-how in their tool kit.