**6.4 Competition with biofuels**

Demand for alternative liquid fuels has driven diversion of cropland to biofuel production, resulting in close coupling between the prices of oil and agricultural commodities illustrated in Figures 8 & 11. Advocates such as Collins & Duffield (2005) are optimistic about the ability of conventional U.S. agriculture to meet world food needs, as well as to make a significant contribution to biofuel production. Sustainability-minded analysts Giampietro & Mayumi (2009), however, argue that biofuels (at least those produced from agricultural crops) reduce food supply, increase CO2 emissions, and retard rural development. Addressing the broader question of meeting a large fraction of human energy needs with biomass, Smil (2010, p. 721) dismisses the idea as an insufferable intrusion on the necessary functioning of the biosphere. Smil does not address specifically either crop residues or grasses as possible biofuel sources, but his general energetic analysis underscores concerns that extensive exploitation these non-crop biological resources would undermine necessary nutrient recycling. Acknowledging the impact of energy prices on food prices and the volatility of food markets, Koning & Mol (2009) call for new institutions to balance food and energy markets.
