Scaling biofuels from the level of the laboratory or pilot-plants to commercial production is the Achilles’ Heel of almost all biofuels. One major problem is that biofuels use feedstocks that are invariably less energy dense than their fossil fuel counterparts. For example, there are approximately 45 MJ per kilogram contained in both the finished product of gasoline and crude oil, while ethanol has an energy density of about 26 MJ per kilogram and corn has only 16 MJ per kilogram. In general, this means that large amounts of corn must be grown and harvested to equal even a small portion of our gasoline consumption on an energy equivalent level, which will undoubtedly expand the land area that is impacted by the production process of corn-based ethanol.

Figure 1. Map of the optimal gradient space for the production of corn-based ethanol within the United States. Colors correspond to EROI numbers listed in the figure caption. The grey areas represent locations without a significant amount of corn-production.