Replacing the gasoline that fuels our cars is no easy thing. Petroleum-based fuels like gasoline and diesel pack a lot of energy and, even though they’re not cheap these days, they still cost less than most – though not all – alternatives. That makes replacing these liquid fossil fuels with more environmentally friendly counterparts a real challenge.
Most of us are aware of the near-term alternatives in limited or demonstration use today, most notably E85 ethanol, biodiesel, and of course those “alternative” fossil fuels, propane (LPG) and natural gas. Beyond these fairly well understood alternatives are little known and somewhat exotic candidates that can also contribute to reducing our dependence on imported oil and decreasing carbon dioxide emissions.
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To be successful, an alternative fuel must work with current engine designs, not the other way around. The reason is simple: Engines that run on gasoline, diesel, or their non-petroleum replacements will be in use and consume fuels in considerable volume far into the foreseeable future.
There are two basic categories of feedstocks for advanced alternative fuels – fossil and biomass. Non- renewable fossil fuels include coal and natural gas. These can be converted to familiar liquid motor fuels through a process called liquefaction using coal-to-liquid (CTL) or gas-to-liquid (GTL) technologies. Biomass fuels produced with biomass-to-liquid (BTL) technology use renewable sources such as plants, organic waste, and algae.
Biomass-based equivalents exist for the three most commonly used transportation fuels today, allowing use of ethanol in place of gasoline, biodiesel rather than petroleum diesel (petrodiesel), and biogas instead of natural gas. In at least small quantities, usually less than about 20 percent, most of these fuels can be used in current engines with little or no modifications. Larger amounts may require some modification but not major engine redesigns. Here’s how five top future fuels stack up.
