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Fuels: More Alternative Fuels
The following fuels are still in the early stages of development or not widely produced due to varying reasons, e.g. economics, feedstock availability, decreased public interest. Each fuel offers benefits in increased energy security, reduced emissions, higher performance, or economic stimulation.
This fuel selection is not meant to be an exhaustive list and will be updated as new alternative fuels are researched and studied. If you feel a particular fuel should be added, please contact us
Methanol
Methanol is also known as methyl alcohol and wood alcohol, and is defined as an alternative fuel when used in blends of 85% methanol and 15% gasoline (M85) or as 100% methanol (M100). Methanol can be used as a substitute for gasoline and diesel in passenger cars, light trucks, and heavy-duty trucks and buses.
The majority of methanol is produced with natural gas as the feedstock because it is more cost effective. Though more expensive, methanol can also be manufactured from other carbon-based fuels including coal and biomass (wood or waste paper).
Methanol is a liquid fuel formed by catalytically combining carbon monoxide with hydrogen in a 1:2 ratio under high temperature and pressure. Because it is produced as a liquid, methanol is stored and handled like gasoline. Methanol is a comparable fuel to ethanol, with similar chemical and physical properties. It has a lower energy content than gasoline, but offers beneficial reductions in exhaust emissions.
Like E85, the majority of methanol is blended with unleaded gasoline to form M85. Most methanol-powered vehicles are fuel-flexible and can run on any mixture of methanol and gasoline up to 85% methanol. M100 is typically used as a diesel substitute.
Methanol is a valuable alcohol for the transportation industry. It can be used to make the fuel oxygenate MTBE. More importantly, methanol is vital to the production of biodiesel. Transesterification is the main reaction needed to convert oil (soybean, rapeseed, recycled cooking oil) into biodiesel. Methanol is needed in the transesterification reaction to produce fatty acid alkyl esters (biodiesel) and glycerin. After the biodiesel and glycerin separate, the methanol is removed, cleaned, and recycled to be used in the process again.
Benefits of methanol include:
- M85 reduces hydrocarbon emissions by 30-40% and M100 offers reductions up to 80%
- Methanol fueled buses emit almost no particulate matter
- Methanol and methanol blends have higher octane ratings than gasoline
- Production costs are low when produced from natural gas
- Lower risk of flammability compared to gasoline
- Biomass produced methanol is biodegradable and dilutes quickly in water
- It can be made into hydrogen and researchers are studying ways to feasibly use methanol as a hydrogen fuel source in future fuel cell vehicles
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Renewable Diesel
Renewable diesel, also called known as hydrogenation-derived renewable diesel, is the product of vegetable oils, either alone or blended with petroleum, that have been refined in an existing oil refinery. Renewable diesel must meet requirements of ASTM D 975 or D 396; renewable diesel does not meet the specifications for biodiesel (ASTM D 6751).
Renewable diesel is mainly manufactured in Finland. It is still not widely available but may soon become commercialized. It is highly expected 100% renewable diesel or any blend will substitute for petroleum-based diesel without modifications to vehicle engines or fuel systems.
Benefits of renewable diesel include:
- An ultra-low sulfur content provides emissions benefits
- Existing infrastructure can be used for processing (oil refineries), transporting (pipelines, trucks), and dispensing (fueling stations)
- Should be able to be used directly in today's diesel engines
Challenges of renewable diesel
There are concerns that vegetable oils or animal fats added to petroleum in refineries will be processed at such a high heat that they will "burn off", leaving very little renewable product left in the renewable diesel. Renewable diesel cannot be tested to see how much renewable product is left in the final fuel and will look, act, and test the same as regular petroleum diesel.
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E-diesel
E-diesel is an experimental, alternative fuel still in the research phase. It is currently being tested in farm machinery, buses, and heavy-duty trucks. E-diesel, formerly called oxydiesel, is a biofuel typically composed of 88.7% diesel, 10% ethanol, and 1.3% additive. Some blends include up to 15% ethanol. The additive is included to add lubricity to the fuel and to prevent the ethanol and diesel from separating, especially at low temperatures or if water contamination occurs.
Companies blending ethanol and diesel receive the federal ethanol tax credit. Ethanol has a lower energy content than diesel and using e-diesel increases fuel consumption compared to 100% diesel. However, the immediate improvement in exhaust emissions when using e-diesel appeals to auto manufacturers seeking to meet the tough EPA emission standards. E-diesel reduces emissions of particulate matter 27-41%, carbon monoxide 20-27%, and nitrogen oxides 4-5%. Because it takes up to 10 years for new engine designs to be phased into the market, using e-diesel is an immediate solution to air pollution.
Concerns with e-diesel include the increased fuel consumption and also safety issues. Ethanol is not as flammable as gasoline but it more flammable than diesel; therefore, to use e-diesel, diesel fuel tanks need safety features similar to those in gasoline fuel tanks.
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Butanol
Butanol can be used as a fuel in internal combustion engines. Butanol fuel can be processed from petroleum but we will focus on butanol produced from biomass fermentation (biobutanol). Biobutanol can be produced from biomass feedstocks such as corn, sugar beets, fast-growing grasses, and agricultural waste products. To be considered an alternative fuel by EPA, 85 percent or more biobutanol needs to be blended with gasoline.
Biobutanol is similar to ethanol, but butanol is a 4-carbon alcohol (butyl alcohol) while ethanol is a 2-carbon alcohol (ethyl alcohol) and biobutanol is less corrosive and tolerates water contamination better than ethanol. However, no vehicle has been approved by auto manufacturers to use 100% butanol but any model that is able to use E10 should be able to use butanol without any problems.
Benefits of biobutanol include:
- It can be produced from domestic biomass feedstocks
- Greenhouse gas emissions are reduced because the CO2 captured by the growing feedstocks balancing the CO2 released during fuel combustion
- It is used as a gasoline oxygenate
- Its energy content is only 10-20 percent lower than that of gasoline
- It can improve the blending of ethanol with gasoline
- It can be produced and distributed through the existing gasoline infrastructure with only minor modifications
However, biobutanol is more expensive to produce than petroleum-based butanol due to the energy intensive purification process. Therefore, butanol produced today is mostly petroleum-based. But with the growing interest in renewable fuels, researchers are working to develop cost-effective methods to produce biobutanol.
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Biogas
Biogas can be used as a substitute to the alternative fuel natural gas and can be used to fuel natural gas vehicles once it has been upgraded to the required level of purity and either compressed or liquefied.
Biogas is produced from the anaerobic digestion (decomposition without oxygen) of organic matter such as animal manure, sewage, and municipal solid waste. Landfills are one of the largest sources of biogas. Large-scale digesters provide biogas for vehicle fuel, as well as electricity production, heat and steam, and chemical production.
Biogas is composed of 50-80% methane and 20-50% carbon dioxide (both greenhouse gases), small amounts of hydrogen, carbon monoxide, and nitrogen, and is usually saturated with water vapor. To purify the biogas for use as a natural gas substitute, the methane is concentrated and all the other gases and water are removed. The result is called biomethane.
Approximately 12,000 vehicles worldwide in 2007 were fueled with biogas; 70,000 vehicles are estimated to be fueled with biogas by 2010. Examples of using biogas in the U.S. include two landfills in California that use the biogas in CNG fueled vehicles and LNG fueled transit buses. View a map of U.S. landfill gas energy projects to see what states are helping to decrease greenhouse gas emissions by capturing landfill gas emissions.
Benefits of biogas are similar to those of natural gas, and include:
- Increased energy security
- Improved worker safety at landfills and public health
- Captured greenhouse gases, capturing methane is especially beneficial because methane is 21 times stronger as a greenhouse gas than carbon dioxide
- Anaerobic digesters for animal waste treat the waste naturally, reduce the amount of material sent to the landfill, reduce waste odors, produce compost and fertilizer, and reduce fecal fecal coliform bacteria (a major source of water pollution) in manure by more than 99 percent
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