Leaks Make Natural Gas Vehicles Less Climate-Friendly Than Diesel

(3BL Media/Justmeans) - A couple of weeks back, we wrote about how natural gas was being used to replace diesel to fuel many large trucks. California-based Clean Energy Fuels Corp. opened several natural gas filling stations in locations stretching from coast to coast. We wrote, “Natural gas has become an attractive option for high-horsepower trucks, because it is less expensive (by up to $1.50/gal), cleaner (23% less GHG emissions), and offers better price stability when compared with conventional diesel. It's also better for the health of drivers and the communities in which they operate. Given the high level of natural gas availability in the US at this time, it also offers the opportunity to reduce dependence on imported oil.“

A recent study, just released, reveals some information that could potentially pour cold water on this approach. The study, which was jointly conducted by scientists at Stanford University, the Massachusetts Institute of Technology and the Department of Energy’s National Renewable Energy Laboratory (NREL), found that there is currently 50% more methane already in the atmosphere than had previously been thought. The researchers have determined that this gas must come from leaks throughout the natural gas supply chain.

After conducting a detailed analysis, weighing both the benefits and costs, the team determined that from a greenhouse gas perspective, the added methane resulting from these leaks, more than offsets the reduction in carbon dioxide resulting from the switch from diesel to natural gas. In other words, according to the study’s lead author, Adam R. Brandt, Assistant Professor of Energy Resources at Stanford, “Switching from diesel to natural gas, that’s not a good policy from a climate perspective.”

The leaks, however, were not severe enough to tip the balance when it came to replacing coal-fired power plants with natural gas. That's because of the enormous amounts of CO2 that comes from coal. Even factoring in the methane leaks, gas-powered plants have half the impact of coal plants.

This finding is clearly a setback for people like Clean Energy Fuels and for the many people who have supported and in some cases, invested in a switch over from diesel to natural gas. But the blow need not necessarily be a fatal one. While the chemistry, which says the natural gas emits 30% less CO2 than diesel cannot be changed, the physics, which allows for the many leaks in the system, can be.

For example, many natural gas wells are located in remote areas where electricity is not available. Many of these use pneumatic controllers that are driven by a flow of natural gas, instead of air as the power source. The gas, after having done its work, is then released into the atmosphere by design. These pneumatic devices include liquid level controllers, transducers, pressure regulators, and valve actuators in numbers estimated at around 400,000. Releases from these devices was estimated, back in 2006, at 50 billion cubic feet.

Under two new EPA regulations, the New Source Performance Standards (NSPS) for volatile organic compounds and the National Emissions Standard for Hazardous Air Pollutants (NESHAP) for oil and natural gas production, the amount of gas that can be vented from these devices is restricted. Installation of newly available, low-bleed units not only allows producers to meet the new EPA standard, but it also saves money by capturing the gas that would have otherwise been wasted.

Now that the magnitude of this problem is better understood, it is clear that we need better regulations and better control measures at every stage of the supply chain. Perhaps, as an example, the pneumatic controllers could, in some cases, be replaced by solar-powered electric controllers that could reduce the bleed rates to zero.

Says Mark Brownstein, chief counsel for the American climate and energy program at the Environmental Defense Fund, “This report justifies E.P.A. taking action on regulation of methane pollution and to focus that regulation on existing wells.”

The industry understands the need and also the opportunity to reduce waste. Of course, they would prefer to not be subject to additional regulations.

Carlton Carroll, a spokesman for the American Petroleum Institute said, “The industry has led efforts to reduce emissions of methane by developing new technologies and equipment, and these efforts are paying off. Given that producers are voluntarily reducing methane emissions, additional regulations are not necessary.”

Of course, the producers will likely take action in cases where it is financially advantageous to do so. The regulations are for those cases where it isn't.

[Image credit: AndyArthur: Flickr Creative Commons]

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