4.2 Environmental Impacts

The research team concluded that:
“Propane is more environmentally friendly than gasoline or diesel, emitting up to 26% less Greenhouse Gases than conventional gasoline and significantly less emissions of criteria air contaminants and air toxics that impact air quality and human health.”

4.2.1 On a Well-to-Wheels basis, propane emits up to 26% less Greenhouse Gases than conventional gasoline
Propane as a transportation fuel can make a contribution to improving air quality and reducing GHG emissions. The US Department of Energy’s Argonne National Laboratory (ANL) examined the full life-cycle Greenhouse Gas (GHG) emissions of propane¹⁴ as compared to other motor fuels. ANL focused on propane as a transportation fuel and analyzed the emissions data in two distinct stages: well to pump (WTP), and pump to wheel (PTW). At the WTP stage, ANL discovered that using propane, in place of diesel, conventional gasoline, or reformulated gasoline, led to a 50% decline in emissions. The ANL study concluded that compared to conventional transportation fuels, propane can reduce full life-cycle GHG emissions by as much as 12 to 20%.¹⁵ Other studies support these conclusions although the numbers vary due to different assumptions and variables.

The Center for Clean Air Policy estimated that a fleet of light-duty GVW vehicles (cars and trucks weighing less than 8,500 lbs.) could achieve a 26% reduction in GHG emissions by utilizing propane fuel instead of gasoline. This 26% reduction in GHG emissions versus gasoline was quantified with ANL’s “GREET Model lifecycle”, which estimated total GHG emissions during fuel production, fuel use and vehicle operation.¹⁶

A recent Glotec report demonstrated that propane emitted between 15% and 27% less gm/mi. of GHG than conventional gasoline on a well to wheels basis.¹⁷

Diesel-powered engines, due to the efficiency of the compression ignition engine and the higher energy content of the fuel, typically deliver between 10 and 20 % fewer GHG emissions than comparable gasoline vehicles.¹⁸ While the GHG emission performance is attractive, diesel engines emit considerably more particulate emissions than gasoline or propane vehicles.

Natural gas, similar to propane, produces fewer toxic and carcinogenic emissions than gasoline and diesel and virtually no particulate emissions.¹⁹ According to the US Environmental Protection Agency, versus gasoline, lifecycle GHG emissions are reduced by 28.5% for Compressed Natural Gas and 22.6% for Liquefied Natural Gas (due to greater energy inputs).²⁰

Ethanol, blended with gasoline in blend ranges from E5 (5% ethanol) to E85 (85% ethanol) is being implemented to reduce the impact of gasoline engine emissions. The U.S. Environmental Protection Agency states that for every BTU of gasoline that is replaced by corn-based ethanol, the total life-cycle Greenhouse Gas emissions that would have been produced from that BTU of gasoline would be reduced by 21.8%.²¹ According to Environment Canada, E10 will produce about 3-4% fewer emissions than gasoline by itself.²²

While the utilization of ethanol-blends results in tailpipe Greenhouse Gas reductions, some of these benefits are eradicated during production. Costs of fuel, typically natural gas, used in the production of ethanol are the second largest expense after the cost for corn feedstock. Increasing natural gas prices have forced ethanol plant owners to explore ways to reduce plant energy costs. Some owners have considered using coal as a less expensive process fuel, but that decision can significantly increase the GHG emissions on a wells-to-wheels evaluation.²³

4.2.2 Propane emits significantly less criteria air contaminants and air toxics than conventional gasoline or diesel, reducing the negative impact on air quality and human health.
The environmental advantages of using propane over conventional or other alternative fuels are even more significant if unregulated emissions, some of which can be toxic, are taken into consideration.

It is commonly accepted that many of the substances emitted from the automobile tailpipe are considered to be harmful to human health. An analysis of transportation fuels must, therefore, include effects on human health in the immediate environment in which they are used. According to the California Air Resources Board (CARB), the substances listed below are among the most toxic substances emitted by vehicle exhausts:

• 1,3-butadiene;
• Formaldehyde;
• Benzene;
• Acetaldehyde; and
• Polycyclic organic matter (POM) associated with particulates.

CARB considers particulate matter from diesel engines to be the most carcinogenic substance, followed by 1,3-butadiene and benzene, respectively second and third on the board’s list.²⁴ Table 3 below, illustrates the release of various toxic chemicals by select transportation fuels and highlights the relative cleanliness of propane. ²⁵

TABLE 3

Toxic chemicals in the air
All data in milligrams of chemicals/mile

Particulate matter (PM) and black carbon (BC) emissions from vehicle exhausts are also thought to contribute to climate change, though the extent of their contribution is being debated in the scientific community. Regardless of the status of the debate, human health concerns related to the carcinogenic nature of fine PM emissions have been the catalyst spurring legislation to lower PM emission tolerance levels for diesel and gasoline engines.

Numerous studies have shown that airborne particles (either solid or liquid) cause serious health problems. The US EPA has estimated that airborne particles cause over 15,000 premature deaths in the United States each year. In addition, scientists have found a correlation between exposure to airborne particles and increased hospitalizations for asthma attacks, worsening of lung disease, chronic bronchitis, and heart damage. Furthermore, a March 2002 study suggests that airborne particles can cause lung cancer. In addition to these human health effects, particulate matter is the main cause of haze, which decreases visibility.²⁶

In a report issued in June 2005, the Ontario Medical Association (OMA) estimated that air pollution would result in almost 5,800 premature deaths and 17,000 hospital admissions this year in Ontario alone. The OMA also estimates health care costs in 2005 at $507 million and total economic costs of air pollution at $7.8 billion.²⁷

According to the Alternative Fuels Vehicle Institute (AFVI), as compared to conventional gasoline, the use of propane reduces particulate matter (PM10) by 40%, nitrogen oxides by 50% and total hydrocarbon (THC) emissions by 87%.²⁸

Although diesel-powered light vehicles emitted GHG’s similar to those of propane-fuelled vehicles, diesel vehicles produced 30 times more PM.²⁹ Not surprisingly, school districts across North America have been among the earliest adopters to convert school buses from diesel to propane. They are driven by two facts: Propane is much cleaner than diesel (and therefore less harmful to the children who ride the buses on a daily basis); and propane cost savings amount to thousands of dollars per bus.

• A study conducted by doctors and scientists from the University of California Berkeley School of Public Health, found evidence that diesel fumes not only are a major source of Greenhouse Gases, but also pose a significant public health risk. ³⁰ Some of their more significant findings are as follows:
• Diesel exhaust causes cancer and premature death and exacerbates asthma and other respiratory illnesses;
• A child riding inside of a diesel school bus may be exposed to as much as 4 times the level of toxic diesel exhaust as someone riding in a car ahead of it;
• Aside from its cancer-causing properties, diesel exhaust is also known to be a major source of fine particles, which can lodge deep in the lungs and exacerbate asthma, a condition most prevalent among children; and
• Over 40 individual chemical compounds in diesel exhaust have separately been listed as TACs. The EPA also identifies these chemicals as compounds that cause cancer.

School boards have been aware of these health concerns for years and have been converting their school bus fleets to propane and saving millions of dollars in the process. The Northside Independent School District in North West San Antonio Texas is an example of a school board eliminating diesel-related health risks and saving taxpayer dollars by converting to propane.