For example, smog can cause eye and respiratory tract irritation, and carbon monoxide can inhibit the ability of a person's blood to carry oxygen to vital organs.
The average vehicle, through its combustion of fossil fuels, also emits greenhouse gases. Greenhouse gases, such as carbon dioxide, methane, nitrous oxide, hydrocarbons, and chlorofluorocarbons surround the Earth's atmosphere like a clear thermal blanket, allowing the sun's warming rays in and trapping the heat close to the Earth's surface. This natural greenhouse effect keeps the average surface temperature at around 60F (33C). However, the increased use of fossil fuels during the last century has created an enhanced greenhouse effect, known as global warming. And transportation has played a large role in this increase.
During the 1990s, the annual growth rate of U.S. greenhouse gas emissions from transportation averaged 1.6 percent. In 1999, some 82 percent of U.S. greenhouse gas emissions consisted of carbon dioxide released by the combustion of energy fuels. The U.S. Environmental Protection Agency (EPA) estimates (Durbin et al, 2000) that each year the average light vehicle in the United States releases 10,000 pounds of carbon dioxide into the air. Motor gasoline contributed close to 300 million metric tons of carbon dioxide, making it the largest single source of U.S. carbon dioxide emissions. By reducing vehicle emissions, AFVs and advanced vehicle technologies help combat both air pollution and global climate change. Alternative fuels not only burn cleaner producing lower emissions, but some are even renewable, unlike fossil fuels, which means we could develop a continuous supply of them. The alternative fuels in use today include ethanol, biodiesel, methanol, natural gas, propane, electricity, and hydrogen.
Biofuels are renewable since they are produced from biomass i.e. organic matter, such as plants. They generate about the same amount of carbon dioxide (a greenhouse gas) from the tailpipe as fossil fuels, but the plants that are grown to produce the biofuels actually remove carbon dioxide from the atmosphere (ERCL, 1999). Therefore, the net emission of carbon dioxide will be close to zero. Diesel engines can function efficiently with biodiesel, a fuel made from vegetable oil. A combination of vegetable oil and diesel fuel produce fewer emissions than straight diesel. Commercially available biodiesel is offered in blends of 5% vegetable oil to 95% diesel (B5), 10% to 90% (B10) and 20% to 80% (B20). Consumers can have their diesel engines converted for around 800 dollars-to run on 100% vegetable oil (Anthony & Cornish, 2001). The oil produces no harmful emissions and the cost can be nominal or free since many consumers get used vegetable oil from fast food restaurants, but consumers must filter their used oil, which is complicated and the equipment is costly. In addition, buying pure vegetable oil can cost more than straight diesel fuel.
Fuel consumption for vegetable oil is similar to diesel, which gets 20 to 30 percent better mileage than gasoline (ERCL, 1999). Emissions are much less toxic than those from gasoline, and its carbon neutral because the carbon dioxide absorbed by the plant from which the oil is derived offsets CO2 generated when it is used as fuel. With the increasing popularity of vegetable oil as a motor fuel,