The term alternate fuels usually applies to automobile fuels that are not diesel fuel or gasoline. Also known as alternative fuels, this term is sometimes used in a broader sense to mean any fuel that is not one of the the standard fossil fuels, such as coal or petroleum derivatives for any type of vehicle, engine, or furnace. With worldwide concern about the sustainability of gasoline as a fuel, research on alternate fuels has grown substantially since the 1970s, although very early work in the field began as early as the 1920s. Today, several types of alternate fuel vehicles are available directly from dealers' lots, and more options are possible in the form of aftermarket conversion kits for certain vehicles that allow the use of one or more alternate fuels. The same concerns over the growing cost of heating oil, natural gas, and propane as well as electricity for home heating has led to the proliferation of many types of furnaces designed to use alternate fuels derived from renewable and sustainable resources.
Research in the field of alternate fuels began in the 20th century, and today, many options are available to those who desire to purchase a vehicle that runs on one of these alternate fuels. In the United States, one of these fuels is ethanol, a type of alcohol usually produced from the fermentation and distillation of corn, is often blended with gasoline and called E85. In other parts of the world, other blends, with varying amounts of ethanol, are available, such as gasohol (E25), or pure ethanol (E100). In each case, the capital "E" stands for ethanol and the number is the percentage of ethanol in the mixture. Other alcohol fuels derived from organic sources, such as butanol and methanol, are sometimes produced and used in certain areas of the world, often blended with gasoline.
Biodiesel fuels are also derived from renewable crops and used to power diesel engines. Biodiesel fuels are chemically nearly identical to diesel fuel that is derived from raw petroleum but are refined from oils that are extracted from plant materials. Raw material for biodiesel, called biomass, undergoes a fairly complex process to produce the biodiesel fuel, but it is very competitive with traditional sources of diesel in terms of price and quality, and in many cases, is less expensive. Diesel engines can also be converted to run on simple vegetable oil, including filtered waste oil from restaurant deep-fryers.
Much work and research has been undertaken to find a way to produce biofuel alternatives and equivalents to traditional fuels, using naturally occurring and genetically engineered algae. Work in this field is relatively new and still being perfected, but it has shown much promise. Algae have been shown capable of producing a number of different fuels, such as bioalcohols, biodiesels, and even biogasoline in amounts that can potentially be commercially viable.
Some other alternate fuels that are being considered are hydrogen, an emissionless fuel in that it produces only pure water when burned. Ammonia, hydrogen peroxide, and new fossil fuels derived from raw petroleum fractions that were previously considered unusable are all possible alternate fuels as well.
In terms of applications besides transportation, particularly residential heating, many alternate fuel furnaces have become available in the last 50 years. Most of these are designed to use fuels that are derived from renewable sources, such as wood pellets that are manufactured from sawdust and other wood based waste. Dried corn cobs are another possibility. These types of furnaces vary greatly in emissions and efficiency, but are increasingly popular as they are generally cheaper to run than traditional fossil fuel or electrically powered units.