The primary use of biofuels will be in the transportation industry. They lend themselves well to transport because they are relatively energy dense (unlike electricity and batteries) and because they are easy to distribute through the current infrastructure with only minor modifications (unlike hydrogen). Further, because biofuels are rather similar to petroleum-based fuels, little modification is required to make vehicles work well with biofuels. In fact, almost all vehicles now burn a blend of petroleum fuel and biofuel.
The primary use of biofuel will be in the motor vehicle segment if for no other reason than the fact that this segment is largest consumer of conventional fuel. The problem with this segment is that it is so vast that meeting the demands with current biofuel technology is difficult if not impossible. This segment, more than any other, is responsible for most of the research and development in biofuels. That being said, there are three biofuels that will play a major role in motor vehicle transport moving forward.
Biodiesel is important because it reacts similarly to diesel fuel, which means it is burned through compression-ignition processes. Compression ignition allows for higher compression within the engine and thus more torque. This translates into more pulling power, which is important in heavy machinery and semis. The major drawback here is that biodiesel is more prone to gelling than standard diesel, which means it is less suitable to cold climates.
Ethanol has become popular as a fuel additive and will remain so for the foreseeable future. Ethanol is easy to produce and non-toxic (unlike methanol), so it is a convenient fuel additive for increasing oxygenation and reducing emissions. The problem with ethanol is its low energy density, which is anywhere from 1/3 to ¼ that of gasoline. Low energy density means that vehicles cannot travel as far on a gallon of ethanol as they can on a gallon of gas. This also means that roughly four times as much ethanol is needed to meet current fuel demands as compared to gasoline, a production level that is unsustainable. Finally, ethanol is corrosive to certain rubbers, so gaskets and seals in engines need to be modified as the level of ethanol in fuel increases.
There is a solution to at least some of the problems presented by ethanol and that solution is butanol. Butanol is also an alcohol, but it contains four carbon atoms rather than the two found in ethanol, which confers several advantages. First, butanol is more energy dense than ethanol, having about 85% of the energy per kilogram as is found in gasoline rather than the 25% of ethanol. Second, butanol is less corrosive to rubbers and can be run in unmodified engines. The only drawback to butanol has been the difficulty in producing it in large quantities. That has changed recently as major companies like DuPont and Danisco have invested in butanol production. Look to see butanol-gasoline blends increase in prevalence in coming years.
AviationAviation is the second largest consumer of energy in the transport industry. The major hurdle to clear in aviation is the need for highly pure, chemically stable fuel. Having jet fuel freeze at 30,000 feet is not a good thing, so biofuels intended for aviation are more difficult to produce than for ground transport. That being said, several companies in Europe have begun to produce jet fuel from Jatropha and are set to begin supplying several major airlines in the near future. Test flights with airlines and the U.S. military have demonstrated that blends of petroleum-based jet fuel and bio-jet fuel are safe and effective.
The other areas where biofuels may make some headway are in shipping and rail transport, but that remains to be seen. As of right now, these industries are not heavily targeted, but given their lower fuel quality standards, fuel produced for other industries should be fully compatible.