Conventional diesel fueled commercial trucks have ruled the roads for decades. Despite the fact that exhaust emissions from diesel engines have been significantly reduced, conventional diesel may not remain the fuel of choice as other options are being considered. Alternative fuel options include biofuel, biodiesel, and natural gas.
Biofuel is a flexible fuel that involves a blend of 85 percent ethanol and 15 percent gasoline marketed as “E85.” The ethanol in E85 is derived from a starch-based process that has not been widely adopted since the starch comes from corn which is a commodity with cyclical price fluctuations. As a result, E85-powered vehicles have not been as popular as previously anticipated.
E85, with ethanol derived from corn, often considered too price volatile for fleet reliance, is being redeveloped using a more advanced process involving the structural mass of plants (such as cellulose, hemi-cellulose, and lignin).
Plant-based, as opposed to commodity-based, ethanol is termed cellulosic ethanol. Cellulosic ethanol is derived from such abundantly available raw materials as switchgrass, miscanthus, and wood chips that are comparatively inexpensive to harvest and have been shown to reduce greenhouse gas emissions.
A major concern with this biofuel, however, is the complexity of the fermentation process necessary to produce the ethanol.
U.S. Department of Agriculture funding and additional tax incentive programs for purchasing ethanol-capable vehicles are expected to help ignite the supply and demand for biofuel commercial vehicles. Ethanol burns cleaner than gasoline, thereby contributing a lower level of pollutants.
Biodiesel for diesel engines
Biodiesel is a non-petroleum-based fuel that can be used alone or blended with conventional petroleum diesel (petrodiesel) in unmodified diesel engine vehicles. When used in a blended mixture, the percentage of biodiesel in the fuel mix dictates its labeling.
For example, a “B20” mix denotes 20 percent biodiesel and 80 percent petrodiesel. Biodiesel fuel, produced as a derivative of processed organic vegetable oil, most often has served as a petroleum-based fuel additive.
The most popular organic sources for the production of biodiesel are rapeseed and soybean oils with soybean being the most preferred ingredient.
Alternatively, animal fats and fish oils can also be used in fuel production. Unlike crop-based ethanol, vegetable or animal derivatives have little other use, thereby creating less fluctuation in product cost; supply, however, remains somewhat unpredictable.
Biodiesel fuels are associated with such environmental benefits as reduction in greenhouse gas emissions, deforestation, and pollution. A major concern for biodiesel storage is the need to maintain a clean supply.
Natural gas needs modified engines
Natural gas, also referred to as compressed natural gas, is considered among the most practical of alternative fuels. A conventional gas vehicle engine has to be modified to create a natural gas vehicle (NGV).
With a huge delivery infrastructure covering most population centers already established, natural gas offers a realistic, widely available alternative fuel.
Although most natural gas is still considered fossil fuel, it contains much less carbon than petroleum fuels. Natural gas can also be derived through organic processes, making it highly appealing. It is important to note that conventional diesel engines can be adapted to natural gas, and can deliver comparable performance results to the diesel version with far lower emissions. Some currently available natural gas engines have already been certified to meet the 2010 exhaust emission regulations.
Natural gas does create the need for a slightly larger vehicle fuel tank. Tax incentives coupled with price differences between natural gas and diesel can result in a possible payback period of 18 to 24 months.
Liquefied natural gas
An alternative is liquefied natural gas (LNG). LNG is a non-toxic, non-corrosive, and non-carcinogenic alternative fuel primarily used in heavy-duty vehicles. LNG is produced by cooling natural gas into a liquid at -260°F and storing it in double-wall, vacuum-insulated pressure vessels. Like compressed natural gas, LNG produces fewer emissions and offers fuel economy comparable to conventional fuels.
Ultra-low sulfur diesel fuel