Nat Gas May Increase Emissions, Group Says

This story appears in the May 25 print edition of Transport Topics.

A switch to cleaner-burning natural gas as a fuel for heavy-duty trucks actually could increase global warming.

That’s because of the release of methane at drilling sites and natural gas-powered engines’ poorer fuel economy when compared with traditional diesel-powered engines, according to the Environmental Defense Fund.

Jonathan Camuzeaux, a senior economic analyst at EDF in Washington, D.C., said“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.”

The report, issued May 19, drew a critical response from Matthew Godlewski, president of Natural Gas Vehicles for America, a trade group that is working with EDF and others to study the methane emissions.

“It’s confusing that the Environmental Defense Fund has chosen to conduct and release another study outside of the cooperative work already under way,” Godlewski said in a statement.

A forthcoming report, in fact, is expected to provide a “critical baseline to end speculation about actual in-use methane leaks from natural-gas stations and vehicles,” Godlewski said.

An estimated 6.3 million metric tons of methane — a primary component of natural gas — escaped into the atmosphere from wells and gas pumping stations in 2013, according to the U.S. Environmental Protection Agency.

In addition, natural-gas truck engines typically are 5% to 15% less efficient than diesel engines because of differences in the energy content of the fuel.

If nothing is done to control methane leaks or boost fuel efficiency, the EDF report said, conversion from diesel to natural gas could lead to greater warming for the next 50 to 90 years before eventually providing a net climate benefit.

Although natural-gas vehicles use just 0.1% of the natural gas consumed in the United States, the volume could rise significantly if fleets step up purchases, EDF officials said.

“Policymakers who want to address climate change should use caution before promoting a switch to natural gas in the trucking sector until we are more certain about the magnitude of methane loss and have acted sufficiently to reduce emission and improve natural-gas engine efficiency,” said Jason Mathers, a commercial transportation expert who works with shippers and truck makers in EDF’s corporate partnerships program.

Trucking’s adoption of natural gas has slowed in the past year because of lower diesel prices, but most experts say they expect conversion to continue as the fueling infrastructure expands.

Ken Vieth, senior partner and general manager at ACT Re-search Co. in Columbus, Indiana, said he expects sales of natural gas-powered trucks to be in the range of 9,000 to 11,000 units this year, about the same as in 2014. Those sales would represent a smaller share of the market as production of heavy-duty trucks is expected to rise by more than 40,000 units to about 338,000 total units in 2015.

Vieth discounted the fact that natural-gas engines are less efficient than diesel counterparts. What matters, he said, is “not how much fuel you use, but what you pay for it.”

Because the price spread between diesel and natural gas has narrowed so much, Vieth said, it will be more difficult for fleets to justify spending more to buy trucks that run on natural gas.

What was a 12- to 24-month payback when diesel was more than $4 gallon is now five to six years, which is well beyond the normal trade cycle of three years for most over-the-road truck fleets, he said.