Forget hydrogen. You can mostly ignore natural gas. Even diesel may not grow much.
The two fuels that will largely power us for the next 20, maybe 30, years are already here. They are gasoline (with some ethanol in it), and electricity.
That's it. That's all she wrote.
Those hallowed green visions of a gasoline-free future in our lifetime will not come to pass. We've spent a century building a global economy around oil, and it will likely take most of another century to change it.
In other words, gasoline will power some of our vehicles for a long, long time to come. It won't power 90-plus percent of our vehicles, as it does today--but far more fuel-efficient gasoline and diesel vehicles will be the single biggest contributors to reducing vehicular energy use for at least the next 20 years, probably longer.
2011 Chevrolet Volt late-night recharging in Little Rock, Arkansas, during July 2010 Freedom Drive
Then, grid power
After that comes electricity. It's widely distributed, the cars that use it are quite pleasant to drive, and within 10 or 15 years, the battery technology will have improved to the point that compact electric cars will have ranges of 200 miles or more. That's enough to make them vastly more acceptable than today's common ranges of up to 100 miles.
Natural gas will probably increase its share, but it may be limited in use, and possibly regional. India and Iran are increasing their production of natural-gas vehicles (NGVs), and the U.S. has domestic supplies in some regions and pipelines across much of the country.
In North America, however, it may become more common for large commercial vehicles than for passenger cars. Globally, Pike Research projects that sales of NGVs will expand at a compound annual growth rate of almost 8 percent, to total 20 million vehicles by 2016.
Goal: carbon neutrality
The end goal should be getting as close as possible to fuels that have a neutral "wells-to-wheels" carbon footprint, which is to say they release no net carbon into the atmosphere.
Today, we're a very long way from that point. But getting solid data on the wells-to-wheels carbon impact of driving one mile using different fuels (and working toward promoting fuels with the lowest carbon impact) is the right way to start.
Today, with U.S. fleet average fuel economy around 25 mpg, a mile driven on electric power is virtually always lower-carbon than one driven by burning gasoline. And that will remain the case until U.S. fleet average fuel economy doubles to 50 miles per gallon, when the gasoline car is better than power from a handful of the dirtiest grids.
But that change will take decades. And that's a major reason plug-in vehicles of all sorts (plug-in hybrids, range-extended electric cars, and battery electric vehicles) make the most sense for the next decade or two.
All about the fuel
Right now, more than 90 percent of a vehicle's carbon footprint is the fuels involved in powering it. According to M.A. Weiss et al., in their 2000 report from the MIT Energy Laboratory, On the Road in 2020: A Lifecycle Analysis of New Automotive Technologies, fully 75 percent of a vehicle’s lifetime carbon emissions come from the fuel it burns over its lifetime.
Corn Ethanol Pump
Another 19 percent is from the production of that fuel. Extraction of the raw materials that make up the vehicle adds another 4 percent, and only 2 percent of lifetime carbon is due to the manufacturing and assembly process.
So the fuel used to power the vehicle is key.
Who are the players?
In our view, the two most viable types of fuels for the medium term are petroleum products (gasoline, diesel, natural gas) and electricity, which already has a distribution system in place.
As for hydrogen, it has enormous challenges to overcome: There's no distribution infrastructure, and it takes enormous amounts of energy to separate out hydrogen molecules from the substances they bind to, whether the source is water, natural gas, or something else. That makes its wells-to-wheels energy balance highly dubious.
Back to gasoline. In the future, it may well be blended with ethanol in higher proportions than it is today. The maximum since 1978 has been 10 percent ethanol, but the EPA last October approved a 15-percent blend (E15) for cars from 2007 to the present, and just last week extended the approval to 2001-2006 models.
But don't expect that to happen any time soon. Carmakers, small-engine manufacturers, and others launched a lawsuit asking that the first approval be overturned.
Over time, we think ethanol will become part of our liquid-fuel mix--perhaps at higher proportions yet, as much as 20 percent. But as currently manufactured, ethanol has several major issues to overcome.