California’s renewable natural gas vehicles turn carbon negative in 2020

Vehicles in California running on renewable natural gas removed more carbon dioxide from the atmosphere than they emitted for the first time last year as the carbon intensity of the fuel continues to drop, according to new data from California’s Air Resources Board (CARB) analyzed by an industry trade group.California adopted measures to decrease the carbon intensity of its transportation sector more than a decade ago, part of a wider scheme to cut greenhouse gas emissions in the state.

The use of renewable natural gas (RNG) in fleets of trucks, buses and other vehicles grew 25% from 2019 to 2020 and is up more than 170% in the past five years, according to the data. Meanwhile, the carbon intensity of compressed natural gas derived from renewable sources (bio-CNG) is dropping as the fuel is increasingly derived from highly carbon negative agricultural waste such as cow manure, according to NGVAmerica President Dan Gage. RNG is also derived from discarded food in landfills and human waste in water treatment plants, which have neutral to positive scores. In 2020 the average annual carbon intensity of bio-CNG was -5.845 gCO2e/MJ – a unit that measures carbon dioxide equivalent per megajoule of energy – compared with 32.735 gCO2e/MJ the prior year, according to the CARB data released in May analyzed by NGVAmerica. “This verified data means (California’s) trucks and buses leave a zero-carbon footprint while virtually eliminating criteria pollutant emissions that contribute to asthma, heart disease, and poor air quality,” said Gage. Natural gas vehicles are still a very small part of the U.S. transportation sector. Of the approximately 180 million vehicles on U.S. roads, only around 175,000 run on natural gas. Much of the freight in the United States is delivered via hard to electrify medium- and heavy-duty trucks, which account for more than a fifth of the industry’s greenhouse gas emissions, even though they make up less than 5% of the road fleet, according to U.S. federal data.

California’s RNG industry started to boom after the U.S. Environmental Protection Agency in 2014 allowed RNG to qualify for cellulosic biofuel credits. REUTERS

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