Government Study Defines Natural Gas Bus Exhaust Issue, Lends Support to Public Policy Decisions Based on Fuel Neutrality
WARRENVILLE, Ill., April 19 -- International Truck and Engine Corporation today underscored the fuel-neutral public policy implications of a study by the California Air Resources Board (CARB) indicating that natural gas vehicles can produce high levels of emissions and pollutants identified by CARB as toxic.
``This new study reinforces the concept that regulatory decisions must be fuel neutral,'' said Dr. William B. Bunn, Vice President, health, safety and productivity. ``Public policies that in any way favor natural gas over diesel should be reconsidered pending peer review of the data in this new study, as well as other research now available.''
The CARB study, released today in Sacramento, found natural gas vehicle exhaust to be up to eight times more mutagenic than diesel exhaust. The government researchers further reported that in 8 of 11 categories of emissions tested, a transit bus powered by natural gas produced higher levels of pollutants than a similar low-emitting diesel bus with low-sulfur diesel fuel, equipped with a particulate trap.
Dr. Bunn commended the California board for undertaking this study and for decisions made by the board last year that recognized the low-emission performance of new diesel engines with advanced aftertreatment technology, using ultra-low-sulfur (below 15 parts per million sulfur content) diesel fuel, now available from BP and other refiners. The performance of a Green Diesel Technology® school bus manufactured by International was certified by both CARB and the U. S. Environmental Protection Agency as meeting particulate and hydrocarbon standards that will be required in 2007 rules in California and nationally.
``CARB's research suggests the possibility of significant adverse health impact from widespread use of natural gas vehicles,'' said Dr. Bunn. ``Assertions that natural gas exhaust is not toxic are not credible. In fact, as this new study corroborates, low-emitting diesel exhaust may include fewer pollutants than natural gas exhaust.''
Conducted as the first stage of research to compare toxicity, ultrafine particulate emissions and the emissions effects of varying duty cycles, the CARB study measured exhaust from transit buses running on natural gas and low- sulfur diesel fuel.
The tests involved two late-model heavy-duty transit buses, one fueled by natural gas and one fueled by ultra-low-sulfur diesel fuel. Currently available technology was used in both vehicles. The diesel bus was tested both with and without the installation of a catalytic particulate filter.
The natural gas bus emissions were found to be seven to eight times more mutagenic than those from the tested diesel bus powered by ultra-low-sulfur fuel and a particulate filter of the type now in use in new diesel vehicles such as the Green Diesel Technology® school bus, in service in California. The natural gas bus was found to discharge more mutagenic emissions, particulate mass, hydrocarbons and carbon monoxide.
Mutagenicity measures the degree of mutation in a cell or organism and is used as a potential health risk indicator for cancer and reproductive health effects. Hydrocarbons are a contributing factor to smog while particulate mass and carbon monoxide are regulated air pollutants.
Dr. Bunn said the CARB study is highly consistent with comparative studies of clean diesel and natural gas, including a comprehensive study by Ecotraffic of Sweden, and a recent peer-reviewed mutagenicity analysis of natural gas conducted by Charles Lapin et al and sponsored by International.
Additional research comparing emissions is under way, including a study by BP in conjunction with the U. S. Department of Energy, according to Dr. Bunn.
In the CARB study, the natural gas emissions were found to contain more gas hydrocarbons, including formaldehyde, butadiene, acetaldehyde and benzene, which have been identified as known carcinogens and a cause of respiratory problems. These hydrocarbons have been listed as ``toxic'' by the California regulatory board.
CARB said the exhaust from the natural gas bus was found to contain fewer nitrogen oxides, nitrogen dioxides and carbon dioxide emissions than the exhaust from the low-sulfur, trap-equipped diesel bus during the testing conditions.
The government researchers reported that they found a high variability in nitrogen oxide emission levels from the natural gas bus. Dr. Bunn said that this variability in the levels of nitrogen oxides emitted calls into question the pollution control impact of natural gas buses when they are in actual service on the road.
International noted that carbon dioxide data vary in tests, while on-road vehicle use confirms diesel vehicles' superior performance related to greenhouse gas emissions. The Swedish study found that natural gas vehicles have higher such emissions than diesel vehicles due to diesel's higher fuel efficiency. A fuel comparison study by the Harvard Center for Risk Analysis in January 2000 said, ``The use of natural gas as a motor vehicle fuel may exacerbate the greenhouse gas effect because methane will escape into the atmosphere during refueling operations and at natural gas storage facilities.'' The Harvard study said that methane is approximately 20 times more ``potent'' as a greenhouse gas than carbon dioxide.
International Truck and Engine Corporation is the operating company of Navistar International Corporation . International Truck and Engine is a leading producer of mid-range diesel engines, medium trucks, heavy trucks, severe service vehicles, and a provider of parts and service sold under the International® brand. The company also is a private label designer and manufacturer of diesel engines for the pickup truck, van and SUV markets. Additionally, through a joint venture with Ford Motor Company, the company will build medium commercial trucks and currently sells truck and diesel engine service parts. International Truck and Engine has the broadest distribution network in the industry. Financing for customers and dealers is provided through a wholly owned subsidiary of Navistar. Additional information can be found on the company's web site at www.internationaldelivers.com .