Gas pumpEnlarge Photo
Currently, the corn-based ethanol used in the U.S. is not economically viable without massive government subsidies (the same could be said for electric vehicles). Gasoline prices will have to rise substantially before it becomes competitive.
Nonetheless, in 2007, the U.S. Congress passed a mandate that the U.S. must use 36 billion gallons of ethanol by 2022. It's not entirely clear how this will happen.
There are also serious questions about the wells-to-wheels carbon balance of corn ethanol, as well as other concerns over its water usage (as high as 8 gallons per gallon of fuel), displacement of food crops, and other concerns.
Canes & grasses
The sugar-cane ethanol used in Brazil is now twice as productive per acre, but import tariffs prevent us from buying it for U.S. gasoline supplies.
The ultimate promise lies in biomass ethanol from things like switchgrass, as well as custom designed algae that gain energy from photosynthesis and actually excrete ethanol compounds. All of those technologies, however, are still in the research and prototyping phase, and they're unlikely to have a noticeable impact for 10 years or more.
GM E85 presentationEnlarge Photo
Automakers, however, like ethanol. Adapting vehicles to run on it is far less costly than engineering electric vehicles from the ground up, and consumers don't have to change their habits. They just have to get used to fewer miles per tank, since a gallon of ethanol contains less energy than a gallon of gasoline.
Electricity better on carbon
At the moment, electricity (even from coal-burning powerplants) has the best carbon footprint per mile driven. Compared to a 25-mpg car, fueling an electric car even on the dirtiest power grid in the country emits less carbon per mile than burning gasoline.
When you double the bogey to 50 mpg, you get a handful of edge cases where burning gasoline is marginally lower-carbon than driving the same mile on grid power.
A 2007 study jointly authored by the Electric Power Research Institute and the Natural Resources Defense Council provides the details. The first volume looks at greenhouse-gas emissions, the second volume at U.S. air-quality analysis.
2011 Ford F-150 EcoBoostEnlarge Photo
Engines get way less thirsty
By 2020 or before, electric cars are likely to be cost-competitive with gasoline vehicles (depending on oil price, of course!) as the price-performance of lithium-ion cells falls at 6 to 8 percent a year, as it has in the consumer Li-ion cell market since 1989.
It's worth noting, however, that gasoline and diesel vehicles will get far, far more fuel efficient with significant doses of advanced technology: turbocharging, direct injection, variable valve timing, and better transmissions.
J.D. Power predicts direct injection will be fitted to 25 percent of U.S. vehicles in 2015; industry analyst IHS Automotive predicts the number will be 38 percent the following year. Almost 9 out of 10 vehicles will have variable valve timing in 2016, IHS says, and turbochargers will comprise either 12 percent (IHS) or 25 percent (J.D. Power) by then.
The full-size sedan of 2025 (e.g. Ford Taurus) might weigh one-third less, have a drag coefficient as low as 0.22, and be powered by a 1.8- to 2.0-liter direct-injected turbocharged engine putting out 300 horsepower--which could conceivably return 35 to 40 mpg in regular use. That's just half the carbon output of a similar car today
What that means is that gas cars will get more efficient fairly quickly, and that's the bar that electric vehicles will have to compete with in 2020 and thereafter.
The infrastructure question
We've spent 100-plus years building a retail distribution infrastructure for gasoline to fuel cars, and that's the strongest.
After that, all households, multiple dwellings, and businesses at least have 120-Volt electricity widely available onsite. While 240-Volt power is needed for recharging battery electric vehicles in practical timespans (6-8 hours vs. 12-16 hrs), that's a much easier problem to solve than building a brand-new distribution infrastructure for another fuel.