As discussed in the trucking industry news site truckinginfo.com, heavy-duty trucks fueled by natural gas will only have their “widely promised climate benefits only if widespread emissions of heat-trapping methane across the natural gas value chain are reduced,” according to a policy-analysis paper published in the American Chemical Society journal Environmental Science and Technology.

Researchers from the Environmental Defense Fund and Columbia University’s Lenfest Center for Renewable Energy co-authored the paper. Researchers from the two groups who wrote the paper say the study’s findings present “implications for truck and engine manufacturers, shippers, fleet operators and policymakers, many of whom look to the operational advantage in carbon dioxide emissions to justify the higher cost and reduced fuel efficiency of a natural gas truck,” the EDF said.

A media briefing held by the EDF on the paper’s results occurred, where Jonathan Camuzeax, a study author and Senior Economic Analyst at EDF, said the challenge to powering trucks with natural gas is that its largest ingredient-methane-has 84 times the warming power as carbon dioxide over a 20-year period.

The Environmental Defense Fund says that even though trucks fueled by natural gas may be considered “running green,” the release of that methane into the atmosphere “all along the value chain” and during each upstream step from production wells up to filling the vehicle’s fuel tanks.

“Natural gas trucks have the potential to reduce overall climate impacts compared to diesel, but only if we clean up the highly potent greenhouse gas emissions from the systems that produce and deliver the fuel,”Camuzeaux said. “Otherwise, the net warming effect is actually a negative one for 50 to 90 years after the fuel is burned.”

That is, a conversion from diesel to natural gas fuelling could lead to great warming for the next 50 to 90 years before it provides any positive climate benefit.

The EDF, an environmental advocacy group, advised that 6.3 million metric tons of methane escaped from the natural gas value chain just in 2013, according to the Environmental Protection Agency’s most recent Greenhouse Gas Inventory Report. The EDF also stated that the level of methane released produces the same negative 20-year climate impact as about 111 million cars or 140 coal-fired plants, and that “wasted gas” amounts to more than $1.42 billion.

However, the Environmental Defense Fund remains optimistic that this wrinkle in the business case for natural-gas trucks will be reconciled and corrected. The study examines several different types of engine technologies and in using both liquefied and compressed natural gas fuels.

The paper’s authors “found that there are indeed pathways for heavy-duty natural gas vehicles to achieve climate benefits, provided methane emissions across the value chain are reduced both upstream and at the vehicle level. Otherwise, a conversion from diesel could lead to greater warming for the next 50 to 90 years before providing [any] climate benefit.”

They cite as evidence for this the face that additional fuel-efficiency improvements can help to make sure natural gas trucks are really climate friendly. The EDF noted that natural gas truck engines are in most cases between 5 and 15 percent less efficient than diesel engines, but “if that efficiency gap can be closed, natural gas trucks will fare that much better compared to diesel.”

In addition, more improvements can be made upstream to cut methane emissions from natural gas fuel production and distribution.

A study from the technology consulting firm ICF International concluded that the oil and gas industry could reduce emissions up to 40 percent for a cost of about one cent per thousand cubic feet of natural gas produced, about one-third of one percent at today’s prices, if they would replace emissions-prone valves and properly maintain pumps and other devices.

“The opportunity is there to achieve a climate benefit, provided we address the powerful emissions both from the fuel supply system and the vehicle,” Camuzeaux said.

At the moment, natural gas vehicles only account for 0.1 percent of the natural gas that is consumed in the United States, but as the rise of heavy-duty natural gas vehicles rises, so too will that figure.

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