The Greenest, Cleanest Car: Better Mileage or Biofuel?

There's no way around it: Your car is contributing to global warming. In fact, it's almost certainly the single most environmentally harmful component of your lifestyle. The transportation sector is responsible for nearly 40 percent of nationwide greenhouse gas emissions, not to mention plenty of ozone-damaging and smog-forming pollutants. The good news is that new clean-car technologies are emerging at a rapid pace — not just behind the scenes, but in the showrooms of car dealerships near you. Efficient hybrid-engine cars like the Toyota Prius and the Ford Escape SUV can't keep up with demand. Meanwhile General Motors and Ford are ramping up their development of flexible-fuel vehicles that can burn both standard gasoline and biofuels such as ethanol. So if you're in the market for a climate-saving, planet-positive vehicle, which should you choose — better mileage or biofuel?

Biofuel

If you listened to President Bush's State of the Union address in January, you may remember his prediction that the future of car technology lies in “woodchips” and switchgrass — two potential sources for so-called cellulosic ethanol, a biofuel that has, indeed, tremendous potential environmental benefits — reducing greenhouse gas emissions roughly 80 percent per gallon of fuel burned compared to standard gasoline. Brazil is already powering most of its cars from cellulosic fuel derived from sugarcane. Unfortunately, all of the ethanol that is currently on the market is corn-derived, which offers only about a 20 percent reduction of carbon dioxide emissions compared to gasoline. Here's why: Substantial amounts of petrochemials are necessary to power the farm equipment and create the fertilizers that are used to harvest corn (very little, however, is needed to grow the crops for cellulosic ethanol). There's another hitch: Even if you buy a flexible-fuel vehicle that burns both standard gasoline and ethanol, it's hard to find fueling stations that offer the oil-alternative, meaning the flexible component can't be put to good use. Today, only about 600 out of the 170,000 fueling station in America offer ethanol-blend fuels.

Better Mileage

Some environmentalists are concerned that the growing attention around ethanol could distract from the much more immediate concern of raising the gas mileage of American cars. It's hard to believe that today's car fleet actually has worse average fuel economy than the 1980 fleet due to both lax regulations and America's love affair with the SUV. But a new force is coming into play — record-high gas prices — and it's encouraging consumers to opt for fuel efficient cars like the 50-mpg Prius. Near on the horizon are plug-in hybrids that have an extra battery unit which can be plugged into a standard outlet and recharged overnight. You can drive about 10 to 30 miles on the overnight power before you start using liquid gas, which means your 50-mpg car now becomes a 150-mpg car. That's great for the planet, and the cost savings are substantial: Current electricity prices yield the equivalent of 70-cent-a-gallon gasoline.

The Upshot

Today, the best environmental bang for your buck is to opt for better fuel mileage. But down the line, we need both technologies: Today's hybrids could be upgraded not only with a plug-in battery, but also lighter materials and a flexible-fuel feature that experts predict could enable them to get up to 700 miles per gallon.

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