Bus Engines

Diesel

For thousands of students who have pulled into the school lot safely in the sea of yellow buses or a group of senior citizens embarking on a trip to the casino in the comfort of a climate-controlled bus, diesel fuel helps makes these excursions possible.

Diesel fuel is cost effective and provides roughly 2- to 3 miles per gallon. Also, the cost of a diesel-engine bus is $300,000 whereas a gas-engine bus costs $30,000 more. While the cost and fuel efficiency may be attractive to keep buses on the road, the emissions from diesel fuel have created a strain on the environment. Alternatives to diesel fuel have been changing the newer fleets of mass transportation that are hitting the streets, especially in towns that are in a constant chokehold of smog and other pollutants.

LNG

Besides diesel, natural gas has been used as fuel for buses. Since natural gas is flammable, there has been a concern that the gas will cause an explosion. Due to this concern, an alternative to the use of natural gas has been developed. This alternative is liquefied natural gas, referred to as LNG. This type of fuel is extracted as a clear, colorless gas that does not produce any odor or corrosive or toxic substances. The conversion process from natural gas to a liquid is called liquefaction. This process involves taking the methane portion of the gas and cooling the substance to minus 259 degrees F, which takes the gas to below its boiling point. Upon completion of this process, concentrations of hydrocarbons, water, carbon dioxide, oxygen, and sulfur compounds are extracted and removed from the of the gas, thus decreasing the amount of emissions polluting the environment. Since LNG is in liquid form, it is half the weight of water, causing LNG to float on top of water if the LNG is exposed to standing water.

LNG comes from major gas reserves in Algeria, Australia, Brunei, Indonesia, Libya, Malaysia, Nigeria, Oman, Qatar, and Trinidad and Tobago, and is transported to import sites in the United States—California, Massachusetts, Maryland, Georgia, Louisiana, and Puerto Rico, a U.S. territory. Within the state of California, there are over 40 LNG terminal locations that are near major roadways. When LNG is received at the terminals, it is placed in insulated containers that are specially designed to keep the LNG cool so it will not evaporate. A terminal LNG site can cost over $1 million. LNG is used for vehicles that have a Class 8 (33,000–80,000 pounds weight) rating.

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