With an absolute glut of renewable energy options for transportation, it's nearly impossible to tell the  winners from the losers.

A new study by Stanford University professor Mark Jacobson separates the best from the rest. He crunched the numbers and found surprising results, among them that corn ethanol may be better than cellulosic. In his paper, Jacobson compared 9 electric power sources and 2 liquid fuel options with respect to 11 important environmental categories such as CO2 emissions, pollution mortality, and land use. To put fuels on par with electricity sources, he used alternative vehicles as the ranking metric.

Wind-powered battery electric vehicles (BEV) demolished the competition by ranking 1st in 7 of the 11 categories, including the highly weighted mortality and climate change reduction events. Second best in the list was wind-powered hydrogen fuel cell vehicles (HFCV), followed by concentrating solar power BEVs, geothermal BEVs, PV BEVs, tidal BEVs, and wave BEVs. Essentially, it looks like the benefits of wind, for now anyway, are so profound that it dragged the less efficient fuel cell over the finish line for a silver medal.

Jacobson believes the United States could replace all 2007 onroad vehicles with wind BEVs by building 73,000 - 144,000 five megawatt wind turbines, reducing US CO2 emissions by 32% and eliminating 15,000 vehicle pollution deaths per year.

BEVs charged by hydroelectric, nuclear, and carbon capture and storage (CCS) coal are part of what the author calls "tier 3" technologies, although Jacobson still recommends hydro based on its load balancing capabilities and health benefits.

At the back of the pack were E85 corn and cellulosic ethanol. But the interesting bit is that corn barely edged out cellulosic due to its smaller land footprint and lower upstream emissions, although both were in the bottom two in most categories. However, I suspect that evolving gains in cellulosic technology will change this over time, which may reveal a larger issue.

This study reflects the current state of things; it's a snapshot. The rankings ignore trends in prices and technology. For example, I fully expect improvements in the hydrogen fuel cell to blow up (ok, maybe not a great word choice) and CCS really hasn't even been seriously piloted.

Still, I think these kinds of comparisons are very informative in this era in which we'll be making far-reaching decisions about our energy future. For now, though, wind BEVs appear to be the best overall bet.