The many problems with ethanol as a fuel have been mentioned here before: the climate and energy security benefits are dubious on a life cycle basis, making it from food crops harms the poor, the economics of cellulosic ethanol remain unknown, it has less energy content than gasoline, it is corrosive, it mixes with water, etc. For these reasons and others, most informed environmentalists completely reject corn-based ethanol as a climate change solution, though many remain hopeful that better feedstocks will be found. Ed Wallace raises yet another objection to its use in motor vehicles, namely that it can damage their engines.
Apparently, gasoline with more than 15% ethanol blended in can damage plastic fuel intakes, corrode surfaces even within special ethanol-tolerant ‘flex fuel’ vehicles, and can attract moisture in a way that can generate acids during storage. I don’t know enough about motor vehicle engines to comment personally, but perhaps some readers will be able to assess the probable severity of these issues.
None of this is to say that ethanol certainly has no role whatsoever in our future mix of transportation fuels. Rather, it suggests that the shift may not be as trouble-free as ethanol’s most enthusiastic promoters suggest. For a whole slate of reasons, the idea that we can easily move from fossil fuel dependence to reliance on domestic crops and ethanol-fuelled vehicles is a falsehood. The process of overcoming fossil fuel dependence will require both more intelligent lifecycle considerations of the total impacts of fuel production and, probably, a greater willingness to alter our overall transportation infrastructure.
Personally, I think hydrogen is a pipe dream and ethanol and biodiesel may find niche roles, but electric vehicles are likely to become the dominant form of ground transport over short-to-moderate distances.