al solar panels, converting sunlight into chemical energy during the photosynthetic “light reactions.” The cells then use this chemical energy to convert carbon dioxide from the air to sugars in a process called the “dark reactions.” The production of biofuels relies on photosynthesis, we can harvest the sugars and biomass produced by plants and process them to obtain fuels that we can use. This process is promising as a short-to-intermediate-term solution, but is limited by the efficiency of converting sunlight into plant matter. Replacing all our fuel needs in this way would require us to cover nearly one third of the United States in biofuel crops.
One way to circumvent the difficulty of both electricity storage and the need for large surface areas in photosynthesis is to link the best parts of photovoltaic cells with the best parts of the biological reactions. Instead of using leaves to conduct both the light and dark reactions, we can now use a man-made device to perform the “light reactions,” converting solar energy to formic acid, an energy intermediate that can be used by some bacteria. The formic acid can then be converted to isobutanol, a gasoline substitute, by a genetically engineered strain of the bacteria called Ralstonia eutropha. This latter process is equivalent to the biological “dark reactions,” and produces a compound that is useful for current-day gasoline-based transportation. By combining these two processes we show how it may be possible to power cars with sunlight or electricity without using an electric car.
This project is supported by Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E). Many teams are working towards similar goals using different approaches through ARPA-E’s Electrofuels Program. The conversion of carbon dioxide to liquid fuel powered by electricity adds interconnectivity among different forms of energy, and may provide the missing link to various energy solutions.
Dr. James Liao is the Parsons Foundation Professor of the Chemical and Biomolecular Engineering Department, University of California, Los Angeles. Dr. Liao also leads a separate project through ARPA-E’s Plants Engineered To Replace Oil (PETRO) Program. This posts originally appeared on the White House’s Champions of Change blog as part of an award that honors individuals who are advancing new ideas that are leading the way to a better energy future.