by Heather Youngs and Chris Somerville  (The Scientist)   Research is underway to reduce the use of food crops for biofuels by shifting to dedicated energy crops and agricultural residues.

…Conversion of biomass is currently the most cost-effective route to produce renewable liquid fuels, and contributes 78 percent of the total renewable energy worldwide.¹ At present, liquid biofuels are derived primarily from plants that are also used for food and feed, such as corn and sugarcane, raising concerns that the industry may not be sustainable in the face of expanding demand for food, feed, and fiber. However, efforts to grow biofuel crops on land unsuitable for food and feed crops, to increase biomass yield, and to facilitate the conversion of biomass to liquid fuels may change that mind-set. With continued improvements, we believe that biofuels can be produced on a large enough scale to meet roughly 30 percent of the demand for all liquid transportation fuels in the United States within 25 years—more than four times the current contribution of roughly 7 percent.

…Thus, one way to increase biofuel production is to take advantage of the leftover plant materials currently being discarded.

…Another potential source of biomass that could be better utilized is woody plants, which have for years been sustainably harvested for lumber and paper. By one estimate, the biomass that is harvested annually in the Northern Hemisphere for wood products has an energy content equivalent to approximately 107 percent of the liquid fuel consumed in the United States. Globally, large areas of land formerly used for agriculture have reverted to forest,³ and the continuing trend to electronic media and paper recycling may reduce the demand for pulp woods. This presents an opportunity to reallocate woody biomass for energy.

…In addition to taking advantage of these existing sources of biomass, we anticipate a shift toward cultivation of plants that naturally produce more biomass per hectare and require less fertilizer, water, and other resources than annual field crops. Perennial C₄ plants, for example, which fix CO₂into a compound with four carbon atoms as part of photosynthesis, are intrinsically more efficient at using light, water, and nitrogen than C₃ species, which fix carbon dioxide into molecules containing only three carbons. Additionally, perennial C₄ plants require less tillage, and perennial root systems add carbon to the soil while protecting against erosion.

…Approximately 18 percent of the Earth’s terrestrial surface, including much of the 600 million hectares of land that has fallen out of agricultural production, is semiarid and prone to drought. Plants that can be grown on such land could dramatically increase biofuel crop production without competing for land used for food crops.  READ MORE