Tailpipe, Crankcase Highest Sources of Methane Emissions in Natural-Gas Vehicles, Study Finds
Vehicle tailpipe and crankcase emissions are the highest sources of methane emissions from heavy-duty natural gas-fueled vehicles and the fueling stations that serve them, according to a study by West Virginia University scientists.
The study — performed by the university’s Center for Alternative Fuels, Engines and Emissions, or CAFEE — was designed to measure and better understand the sources and amount of greenhouse-gas methane that is emitted across the natural-gas supply chain, the Morgantown, West Virginia-based center said.
Data from this research are being applied to develop models to forecast methane emissions from the transportation sector, and a novel measurement system was developed to quantify methane leaks and losses, according to the center.
Pump-to-wheels methane emissions from the heavy-duty transportation sector, which have climate change implications, are poorly documented, it added.
The study attributed 39.1% of the emissions to the engine crankcase and 30.6% to the tailpipe.
Methane is the key constituent of natural gas, and a GHG with a global warming potential more than 25 times greater than that of carbon dioxide, according to the U.S. Environmental Protection Agency.
“Natural-gas vehicle and dispensing technology has evolved steadily. We characterized methane emissions from real-world operations to support well-informed projections of future pump-to-wheels contributions from heavy-duty vehicle use,” Nigel Clark, who chairs the university’s engineering department, said in a statement.
Engine-related emissions were characterized from 22 natural-gas fueled over-the-road tractors, refuse trucks and transit buses. Losses from six liquefied natural gas and eight compressed natural gas stations were characterized during compression, fuel delivery, storage and from leaks, the center said.
“The natural-gas vehicle industry has taken a proactive approach to reducing methane emissions,” NGVAmerica President Matthew Godlewski said in a statement.
“The findings confirm that many of the technologies being deployed on the latest generation of natural-gas engines and refueling infrastructure are dramatically lowering emissions and continue to make natural gas the ‘greenest’ choice for fleets across North America,” he said.
Washington, D.C.-based NGVAmerica is an advocacy group promoting use of more clean-burning natural gas in transportation.
The university’s CAFEE is the group that discovered certain passenger cars manufactured by Volkswagen AG were cheating on emissions levels.
