A 2007 article by Groom et al. in Conservation Biology reviews different variants of biofuels and their impacts on biodiversity. The authors acknowledge biofuels’ capability to lessen or slow the effects of global warming; however, they stress the importance of regulation and legislation in order to preserve both diversity and maintain a beneficial energy input: output ratio. Their results are interesting. They examined five broad categories of biofuels: grasses, woody biomass, residues, oil crops, and microalgae. Corn based ethanol, the most commonly used biofuel in the U.S., is worst for decreasing biodiversity and has the worst energy conversion efficiency of only 10-25%. At the time of this study, the energy conversion efficiency for microalgae based biodiesel was not available. Although these data were unavailable, the authors conclude microalgae are the most promising biofuel. This conclusion is derived from the fuel yield per hectare: corn yields between 1135 and 1900 litres per hectare; microalgae yields between 49,700 and 108,800 litres per acre. Most other fuels fall in between these two when all factors are considered. The advantages and disadvantages of each source are discussed in detail. The largest problem with using both woody biomass and crop waste as a fuel source is that of erosion. Obviously, growing corn for fuel reduces land area for crops or reduces biodiversity when new land is cleared. Microalgae, on the other hand, have none of these problems. Brackish and even salt water can be used for growing this valuable crop. Furthermore, the area needed to produce 50% of the nation’s transportation fuel is only 1.5 to 3.2 million hectares. Corn would require at least 90.6 times that area (290-485 million hectares). The article can be found at the following url: < http://journals.ohiolink.edu/ejc/pdf.cgi/GROOM_MARTHA_J.pdf?issn=08888892&issue=v22i0003&article=602_babpfcbpfbp >.
Groom, M. J., E. M. Gray, & P.A. Townsend. 2008. Biofuels and biodiversity: Principles for creating better policies for biofuels. Conservation Biology. 22:3, 602-609.