Environmental Benefits

When it comes to breathing easier and protecting our environment, replacing old diesel buses with new propane buses is an easy choice. Older diesel engines are notorious polluters, harming both people and our environment, while new propane buses have the smallest air pollution impact of any fossil fuel option.


Prior to the adoption of new diesel standards in 2007, diesel engines were allowed to put out ten times the level of particulates than newer engines. And close to three-quarters of Florida’s school buses were manufactured before the new standards went into effect, so Florida schools are running fleets of very dirty buses.

The tiny particles emitted by diesel engines are a big problem for human health because these tiny particulates are so small, they can get by our usual defenses and get stuck deep in our lung tissues. These particles carry with them toxic heavy metals, sulfates and many other chemicals. They are so dangerous that the EPA established rules on how long school buses can idle in school yards. This is because children are among the most susceptible to the effects of diesel emissions, potentially causing serious health conditions such as asthma and severe allergies. Diesel emissions also harm people with cardiovascular and respiratory disease and chronic heart or lung disease and senior citizens. Finally, studies reviewed by the state of California indicated that people who work around diesel engines, including drivers, may have a higher likelihood of lung cancer. Replacing these old fleets with propane buses helps to eliminate these risks and threats.


Another downside of diesel engines is that they have higher levels of nitrogen emissions than propane engines. Older diesel engines put out four to sixteen times more nitrogen than new propane engines. Even newer diesel engines emit 20% more nitrogen than their propane counterparts.

Nitrogen pollution is bad for both our air and water quality. In the air, nitrogen air pollution contributes to ozone depletion, smog and acid rain. This same atmospheric nitrogen also finds its way into Florida’s estuaries, where it “fertilizes” harmful algae growth, causing damage to sea grass beds that keep our bays clean and provide habitat for sea life. According to the Tampa Bay Estuary Program, atmospheric loading of nitrogen amounts to about 25% of nitrogen loading to Tampa Bay, with most of this coming from transportation sources. So a key strategy for maintaining and improving the water quality and overall health of Tampa Bay and other estuaries is to reduce atmospheric nitrogen pollution.


Propane is one of the most attractive options for reducing greenhouse gas emissions in just about any application. According to the U.S. Department of Energy, propane is a cleaner burning fuel than gasoline or diesel because it has a lower carbon content. As a consequence, propane has lower life cycle emissions than other conventional fuels. Specifically, propane emits fewer greenhouse gases at the point of use than gasoline, diesel, heavy fuel-oil or E85 ethanol products per unit of energy. And while natural gas does emit fewer greenhouses gases at the point of combustion, it is also very stable when it is released into the air (as methane), so that it has 25 times the negative impact of carbon dioxide. The bottom line is that when propane is considered as a fuel from point of extraction to final combustion, it has the lowest greenhouse gas impact of any fossil fuel option.