A Sustainable Path for Energy Production and Use

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Biofuels

Biofuels have been proposed as a particularly attractive option to address the projected shortfalls in the demand for liquid fuels. A biofuel is produced from plant-based (and thus renewable) materials that are transformed by physical, chemical, and/or biological processes. Although ethanol and biodiesel are the best-known biofuels, other fuels such as butanol and hydrogen will become important.

The term “biorefining” is used to represent the concept that many other molecules can be produced in conjunction with biofuels (e.g., nutraceuticals), just as is the case with petroleum refining, with the effect of enhancing the cost-competitiveness of biofuel production. Biofuels can be produced domestically, potentially providing a buffer against price fluctuations and geopolitical uncertainty. The production of biofuels provides local employment opportunities. Finally, the carbon dioxide produced by the combustion of biofuels is offset by the photosynthetic uptake of carbon for plant growth, thus approaching a fuel production system that is nearly carbon-neutral. Although US starch-based ethanol production recently surpassed 4 billion gallons/yr, this technology has significant limitations in terms of water consumption, land use, and energy conversion.

As the US moves toward using renewable sources to replace a greater fraction of the 14 million barrels/day (215 trillion gallons/yr) of crude oil used for transportation, it is clear that major changes and innovations are required for all aspects of biofuels production.