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California’s Transportation GHG Problem Is Urgent—RNG Can Help

By Thomas Lawson

With Gov. Jerry Brown’s new executive order calling for California to cut overall emissions to zero by 2045—and then go negative—the stubbornly high greenhouse gas emissions from the state’s transportation sector loom larger than ever. Accelerating purchases of electric cars must be part of the solution, but it’s not the only path the state should be pursuing. Reducing emissions from heavy-duty trucks is also essential—and there’s a carbon-negative fuel that can help us make real progress right now.

Renewable natural gas, also known as RNG or biomethane, is the lowest-carbon fuel available on a full fuel-cycle basis (production to end use), reducing greenhouse gas emissions through both its production and use, according to the California Air Resources Board. It could replace millions of gallons of the diesel fuel that powers 95 percent of trucks in California, benefiting both climate and human health: These trucks and other heavy-duty vehicles produce a disproportionate share of emissions—20 percent of transportation-related greenhouse gases nationally, about 50 percent of smog-forming emissions and more than two-thirds of toxic diesel particulate pollution.

RNG is made by capturing methane—a potent short-lived climate pollutant—that would otherwise flow into the air from landfills, wastewater treatment plants, food waste, and dairies and other large agricultural operations. When produced from food waste, RNG powering a heavy-duty truck has a carbon intensity of negative 25.5. RNG from other sources has carbon intensity scores ranging from 8.6 to 26.2 when used in heavy trucks. (That compares with 38.9 for a battery electric truck running off California’s average electrical grid mix.) Those scores are even lower when RNG is used in trucks with near-zero natural gas engines.

The near-zero engines also produce almost no nitrogen oxides (NOx), a primary component of smog, or black carbon. Putting RNG-fueled near-zero heavy-duty trucks to use at scale would immediately benefit the communities, like those surrounding the Port of Oakland, that are suffering the most from exposure to diesel exhaust. The health effects these communities face are severe: premature death, hospitalizations and emergency department visits due to asthma and other chronic conditions, and decreased lung function in children.

Deploying trucks powered by RNG could also create as many as 130,000 good-paying jobs in California—in RNG production, truck and fueling infrastructure, and related fields—and add $14 billion to the state’s economy by 2030, according to an analysis by the transportation consulting firm ICF.

We can make much of the fuel in-state. The University of California, Davis, Institute of Transportation Studies forecasts that California could produce 750 million gallon equivalents of RNG annually. In Sacramento, for example, ReFuel Energy’s natural gas station is partnering with a Sacramento biodigester facility that can turn a load of food waste into transportation-grade RNG in just 21 days. The facility is designed to accept 100 tons of food waste every day and could replace more than 600,000 gallons of diesel with RNG every year.

So what’s the catch? There isn’t one, really. Failure to jump on the RNG opportunity is mostly about policy choices. California traditionally has run fuel-neutral incentive programs for the development and purchase of alternative fuels and vehicles, and they are bearing fruit across the board—with advances in biofuels and hydrogen as well as electric technology. But recently there’s a push to limit incentives to electric vehicles. That would virtually guarantee continued high emissions from the heavy-duty sector for another decade or so, given the limited number of heavy-duty EV solutions available now and the standard turnover time for heavy-duty fleets.

We can’t afford that. Considering the recent assessment of how far California has to go to reduce greenhouse gas emissions from transportation, we should be putting every clean fuel to use, wherever it makes sense.

Thomas Lawson is president of the California Natural Gas Vehicle Coalition. He also was director of the Office of Legislative Affairs for former California Attorney General (now U.S. Senator) Kamala Harris and served three Assembly speakers.

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