Alternative Fuels

Study Measures Methane Impact of Natural Gas Vehicles

Posted on February 15, 2017
Research by West Virginia University scientists sheds light on the sources and amount of greenhouse-gas methane emitted across the natural gas supply chain. Photo courtesy WVU
Research by West Virginia University scientists sheds light on the sources and amount of greenhouse-gas methane emitted across the natural gas supply chain. Photo courtesy WVU

A new study expands on the previously limited data on methane emissions from heavy-duty natural gas vehicles and refueling stations.

West Virginia University (WVU) scientists at the Center for Alternative Fuels, Engines and Emissions conducted the research, which was recently published by Environmental Science & Technology.

According to WVU, the pump-to-wheels study is the first end-use paper in a collaborative scientific research series designed to measure and better understand the sources and amount of greenhouse-gas methane that is emitted across the natural gas supply chain.

Natural gas-fueled vehicles are expected to play an increasing role in meeting future transportation fuel needs. By relying on a cleaner-burning fossil fuel, natural gas engines can produce less greenhouse gas emissions than diesel, according to WVU, but only if methane emissions are kept low.

Researchers are applying the study’s data to develop models to forecast methane emissions from the future heavy-duty transportation sector. The research aims to help the industry target improvements in engine technologies and fueling operations, and identify best practices for minimizing emissions.

“Natural gas vehicle and dispensing technology has evolved steadily,” said Nigel Clark, a WVU professor and one of the authors of the study. “We characterized methane emissions from real-world operations to support well-informed projections of future pump-to-wheels contributions from heavy-duty vehicle use.”

Researchers looked at methane emissions from the pump-to-wheels sector of the natural gas supply chain and characterized emissions factors for each major source associated with currently manufactured heavy-duty vehicles and fueling systems. The researchers studied 22 natural gas-fueled transit buses, refuse trucks, and over-the-road tractors, and six liquefied natural gas (LNG) and eight compressed natural gas refueling stations.

Scientists also examined cryogenic boil-off pressure rise and pressure control venting from LNG storage tanks. Vehicle tailpipe and crankcase emissions were found to be the highest sources of methane.

Industry group NGVAmerica said that the WVU study provides valuable insights for understanding emissions from natural gas vehicles and fueling stations.

“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,” said Matthew Godlewski, president of NGVAmerica.

The WVU study is available here.

Related Topics: alternative fuels, CNG, emissions

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