Carnegie Mellon University
June 05, 2015

Researchers Shed New Light on Natural Gas-Powered Trucks

By Tara Moore / 412-268-9673 /

Tractor Trailer

Researchers in Carnegie Mellon University’s College of Engineering have concluded that switching from petroleum-based fuels to natural gas-based fuels offers very little to no potential for greenhouse gas (GHG) emissions reduction in heavy-duty vehicles like buses and tractor trailers.

The results, which were recently published in Environmental Science & Technology, could act as a key influencer in environmental policy debates on using natural gas for transportation.

The low cost of shale gas has sparked a growing interest in the topic of natural gas-based fuels and an overarching assumption that this fuel source is cleaner.

“There is a lot of interest in how natural gas-based fuels should be used in vehicles, especially heavy-duty vehicles, to reduce emissions,” said Paulina Jaramillo, assistant professor of engineering and public policy (EPP) and co-author of the paper. “Natural gas may not help us reach this goal. It is worth rethinking if we are going to indeed use natural gas-based fuels or if we instead need to focus on electrification.”

Jaramillo and her co-authors, EPP Ph.D. student and lead author Fan Tong and EPP Associate Professor Inês Azevedo, performed a comparison of natural gas-based fuels in medium and heavy-duty vehicles using five different types of vehicle engines. They specifically focused on estimating the emissions of three greenhouse gases: carbon dioxide, methane and nitrous oxide.

“While natural gas could be used in transportation in many ways, ranging from compressed natural gas (CNG) and liquefied natural gas (LNG) to using natural gas to produce electricity, we find that different natural gas-based pathways have different consequences in terms of greenhouse gas emissions,” Tong said. “While using natural gas-based fuels (electricity and hydrogen) in electric vehicles could reduce GHG emissions, other current technologies that use natural gas-derived fuels do not offer any significant opportunities for large emission reduction in heavy-duty vehicles.”

Although the study focused on greenhouse gas emissions, it recognizes that there are other potential environmental benefits to using natural gas for road transportation. In order to further explore these benefits, the authors plan to look at the potential benefits of reducing air pollutants.

The paper, the first study to include all viable pathways for natural gas as a fuel, lays the groundwork for further discussion on how natural gas-based fuels should be used in vehicles.

“Emission reductions could be higher if there are significant improvements in process and increased vehicle efficiencies,” Azevedo said.

Read “A Comparison of Life Cycle Greenhouse Gases from Natural Gas Pathways for Medium and Heavy-Duty Vehicles.”