Washington, D.C. (August 26, 2002) – Preliminary test data from the California Air Resources Board (CARB) shows, yet again, that today’s natural gas-powered transit buses are better for the environment than comparable diesel-powered buses.

The study results, the product of the second phase of a CARB study testing the emissions from natural gas transit buses and diesel-powered transit buses, found that natural gas bus engines in commercial production emit fewer toxic emissions than either conventional diesel buses or prototype diesel bus engines that are not yet in service. In fact, the CARB report states “[t]esting of the CNG technologies challenged the sampling and analytical methodologies to the limits of detection.”

In April 2002, CARB released the results of the first phase of a transit bus study comparing the emissions from an in-service older model natural gas bus to a prototype diesel bus upgraded with a state-of-the-art oxidation catalyst and a continuously regenerating diesel particulate filter, and operated on ultra-low sulfur diesel (less than 11 parts per million (ppm) sulfur) that will not be widely available until at least 2006. This second phase tested two currently available natural gas buses just fitted with oxidation catalysts that are more reflective of the natural gas engine technology available today.

“These results, while preliminary, support what the NGV industry consistently has said, namely, that, with comparable technologies, natural gas vehicles are – and will always be -- cleaner than diesel vehicles,” said Richard Kolodziej, president of the Natural Gas Vehicle Coalition.

While both the prototype technology diesel and currently available natural gas technology buses produced far fewer toxic emissions than conventional diesel technology, the natural gas buses produced less than half the NOx of the comparable diesel bus. NOx is a major contributor to smog, which as been linked to many health problems including asthma, respiratory disease.

Of special concern are nitrogen dioxide emissions. According to the Environmental Protection Agency, the health effects of exposure to NO2 are similar to those of ozone. Short-term exposure decreases lung function, with even very low levels causing lung irritation. Long-term exposure can destroy lung tissue, leading to emphysema. The advanced diesel bus produced between four and eight times more NO2 than the natural gas buses.

“If air quality is a concern, studies such as this one will make it difficult for local transit fleet operators to justify continuing to buy diesel buses,” said Kolodziej. “When you couple that with the anticipated loss in efficiency, reduction in durability and increased cost of diesel engines meeting the new EPA emission standards, the advantages of natural gas buses become even greater.”

As to particulate matter (PM), the advanced diesel bus produced emissions that were comparable to the natural gas bus. However, it should be noted that the natural gas bus achieved these low PM numbers without the need for any particulate trap technology.

The studies prove it: factory-built NGVs greatly reduce harmful emissions compared to similar gasoline vehicles. NGVs produce:

98% lower smog-forming volatile organic compounds (VOCs) — One of the main health hazards associated with vehicle emissions is ground-level ozone. VOCs react with NOx to form ground-level ozone, a major component of smog.

90% lower carbon monoxide (CO) — Carbon Monoxide is a toxic gas formed by the incomplete combustion of fuels. At high concentrations, CO can pose an acute health threat. Lower doses of CO commonly found in cities during traffic congestion may impair perception and reflexes.

50% lower nitrogen oxides (NOx) — Not only is NOx play essential in causing ozone and smog, it also contributes to acid rain. Nitrous oxide is also a greenhouse gas and the build up of greenhouse gases in the upper environment contributes to global warming.

60% lower particulate matter (PM) — PM is a microscopic component of air pollution that penetrates deeply into the lungs. According to a recent U.S. Environmental Protection Agency report, PMs are more harmful than originally suspected, increasing respiratory and cardiovascular problems.

97% lower sulfur dioxide (SO2) — Natural gas contains very little sulfur and therefore NGVs will have very low sulfur dioxide emissions. Sulfur dioxide contributes to air pollution and acid rain.

Lower NMHC emissions — Natural gas is inherently lower in NMHC Non-Methane Hydrocarbons than other fuel types. Hydrocarbon emissions consist of a mixture of VOCs which are highly reactive. The purpose of limiting total hydrocarbon emissions is to limit VOCs. Emissions standards specify limits only on Non-Methane Hydrocarbons (NMHC).

Zero Benzene emissions — Natural gas contains no benzene. Benzene is a common constituent of gasoline and gasoline engine exhaust. It is a well-known carcinogen and considered a toxic air contaminant.