What would be the land use impact of recovering fuel from biomass? We have developed a crude estimate of the amount of land needed to meet all liquid fuel demand in the U.S. using grain alcohol. The current land base supporting grain, wheat, and bean production in the U.S. is approximately 100 million hectares. Non-wheat grains comprise approximately half of this, or about 40 million hectares. Of this amount, about 23% is now devoted to ethanol fuel production (i.e., ~ 9.3 million hectares), and this amount produces 3% of U.S. fuel. The global average fraction of fuel from ethanol is closer to 5%.
Using the global value, the world would need to increase ethanol production by 20-fold over current levels to meet 100% fuel needs from grain ethanol. In the U.S. this equates to an increase in the area planted in non-wheat grains from 9.3-162 million hectares, an increase that would exceed the total available cropland by almost twofold and increase grain-producing areas by fourfold. If we assume that this relationship holds for other grain- and crop-producing areas of the world, this would equate to a fourfold increase worldwide. We can discount this slightly by 10% to account for yield increases and perhaps another 10% to account for currently available idle land.
It is clear from these numbers that the land base would have to overrun the cropland area for current croplands and spread into other regions (tropics) and ecosystems (forests). This finding is consistent with recent studies by Searchinger et al. (2008) and Fargione et al. (2008). In addition, such a transformation would increase the net carbon debt of biofuels through carbon stock loss due to land conversion.
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