Carbon dioxide (CO2) is the baseline for emissions in the scientific community's calculation of global warming potential (GWP) and is part of a rudimentary understanding of emissions metrics needed in the alternative fuel transportation sector, according to a white paper released Monday by the trade group Natural Gas Vehicle (NGV) America.

CO2 is a universally used metric in calculating greenhouse gas (GHG) emissions and climate change impacts because it is the dominant GHG in terms of annual emissions, the authors wrote in "Understanding Global Warming Potential and other GHG Emission Metrics."

The white paper noted that methane, a prevalent source of GHG, stays in the atmosphere a relatively short time, about 12 years, while CO2 can stay for hundreds of years.

"By comparing GHG to CO2 over a specified time frame, the user is able to make the appropriate choice in determining the best technology available," the report said, noting that GWP is the most common emission metric used today.

NGVAmerica's Dan Bowerson, director of technology and development, said there is ongoing debate about what are the best methods for analyzing GHG. The white paper attempts to explain the differences in approaches in GWP, global temperature potential and technology warming potential .

"Understanding each of these metrics is critical to understanding the results of any GHG comparison between fuels, vehicles, power plants, etc.," according to the white paper.

While the industry is "demonstrating its ability to dramatically reduce the amount of methane emissions" along the entire supply chain, natural gas used as a transportation fuel provides "an immediate reduction" in long-lived CO2 emissions.

The report is a product of an emissions and environmental work group, comprised of multiple member companies.

Meanwhile, Wood Mackenzie analysts estimated that liquefied natural gas (LNG) use in trucking will double in China by 2025, and the Chinese market would be the world’s largest for LNG heavy-duty vehicles. A separate report last month by the Brookings Institution also noted that China was the world's fastest growing market for LNG imports.

Last year, Wood Mackenzie reported that China absorbed 19 metric tons of LNG for trucking, and it projected that volume will grow to 38 mt in 2025.

"LNG trucking has played a key role in supporting gas demand in China, especially in the last winter season when the nation faced severe gas shortage issues," Wood Mackenzie analysts noted.

LNG in trucking provides China with flexibility, alleviating its lack of pipeline coverage, storage and regasification capacity, said analysts. LNG use in the trucking sector also has helped create more gas-on-gas competition and more of a spot market in China.

Also, as an outgrowth of state and regional efforts aimed at cleaning up goods-hauling trucking fleets, particularly at the major ports, a collaborative effort in California turned out the first near-zero emission 12-liter NGV truck.

The port drayage and mail delivery trucking fleet AJR Trucking Co. took ownership of the first truck equipped with the Cummins Westport ISX12N, the only engine certified by the California Air Resources Board as meeting the toughest national standards. Kenworth Truck Co. provided the rig, and the California NGV Partnership worked to provide incentive grants to AJR's owners.

Eligible fleet owners could receive up to $100,000/truck toward the purchase price of a new vehicle to replace aging diesel trucks. Sempra Energy's Southern California Gas Co. helped AJR Trucking submit 46 Prop 1B applications and eventually get grants for the purchase.

Similarly, a Pennsylvania Department of Transportation-managed program said compressed natural gas (CNG) fueling stations have opened at local transit authorities in New Castle and Meadville, PA, by Trillium CNG Inc.

Pennsylvania has a 20-year program that is slated to provide CNG to more than 1,600 transit system buses.