Biodiesel pump (© Jacob Gordon)Click to enlarge picture

Biodiesel contains about 9 percent less energy than petroleum diesel, but it has a higher cetane rating (which promotes more-efficient combustion) and better lubrication properties.

Instead of a wholesale switch to electric cars, with all their inherent range and charging problems, a seemingly easier way to wean ourselves off gasoline is to find alternate fuel that could be used in slightly modified internal-combustion engines. Unfortunately, there are some very real reasons — never mind what conspiracy theorists might tell you about oil companies and corrupt government officials — why most alternative fuels are not ready for prime time yet. Here's a look at the current status and near-term future outlook of the major alternatives to gasoline.

Clean Diesels
Modern turbo-diesels get about 30 percent better fuel economy than their gasoline counterparts, have gutsy low-rpm torque, and work well in vehicles with automatics and for towing; they're a seemingly perfect solution for the U.S.

Unfortunately, diesel emissions are far dirtier than gas emissions. Removing diesel's pollutants requires costly pieces of emissions equipment. Diesel also requires approximately 30,000-psi fuel-injection systems. These costs make diesels more pricey than even turbocharged, direct-injection gasoline engines, and those gas engines have the potential to achieve about two-thirds of diesel's fuel-economy advantage.

While diesel costs about the same as gas today, it has run as much as 30 percent higher — and it is taxed at a higher rate than gas. There's no easy fix to keep diesel prices low, relative to gas, because American refineries, in general, produce about 19.5 gallons of gasoline and 10.3 gallons of diesel from each barrel of oil. That means a gas-powered vehicle getting 20 mpg can drive about 390 miles on a barrel of oil, while a diesel, at 26 mpg, can go only 270 miles.

Since a barrel of oil doesn't go as far in a diesel car, a wholesale conversion to diesels is unlikely in America unless we suddenly figure out how to make diesel fuel from something other than petroleum. European refineries produce more diesel and less gasoline from each barrel of oil, but making that switch would essentially require building brand-new refineries. Don't hold your breath.

One approach is to transform animal fat or vegetable oil, via a transesterification process, into what is called "biodiesel." The resulting fuel doesn't contain sulfur and can be used in pure form, though many vehicle manufacturers recommend that it be blended with petroleum diesel in proportions between 5 and 20 percent. Biodiesel contains about 9 percent less energy than petroleum diesel, but it has a higher cetane rating (which promotes more-efficient combustion) and better lubrication properties.

Despite America's appetite for french fries, there isn't enough used cooking oil to make very much biodiesel. In fact, it has been suggested that to replace all of our petroleum needs with biodiesel would require the planting of soybeans on all of the arable land in the United States. New approaches for making biodiesel from algae are being explored, but they are likely decades away from mass production. Until then, biodiesel's limited availability and higher cost will keep it a bit player.

Synthetic Diesel
Another diesel alternative is synthetic diesel, made by a variety of chemical conversion processes that transform natural gas, methanol, or coal into diesel. The resulting fuel is usually sulfur-free and has a higher energy content than petroleum diesel, plus cleaner exhaust emissions. Converting natural gas to diesel fuel, also known as "gas-to-liquid," makes it easier to transport because it requires no refrigeration or compression.

The cost of synthetic diesel is also reasonable, although the environmental and energy-independence benefits are minimal. Converting coal to diesel creates much more carbon-dioxide emissions than simply using petroleum diesel. In fact, this is a problem, in varying degrees, with any of the synthetic-fuel processes. However, North America has plentiful natural-gas reserves, and this could be a simple way to convert it into an easy-to-use motor fuel.