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Growth in carbon neutral RNG spotlights debate on electric- vs. renewable-powered trucks

Renewable natural gas volumes and carbon benefits are on the rise

(Photo credit: Jim Allen/FreightWaves)

Renewable natural gas (RNG) is having a moment, and California, naturally, is at the epicenter.

In 2020, a company that sells renewable natural gas to California medium- and heavy-duty trucking fleets can charge as much as $10-$12 per diesel gallon, according to Cliff Gladstein, president of Gladstein, Neandross & Associates (GNA), a leading clean transportation consulting firm.

“You can make a lot of money,” he said, repeating himself for emphasis. “A lot of money.”

The environmental benefits also are on the rise. The California Air Resources Board (CARB) released data recently showing that the average “carbon intensity” of all renewable natural gas vehicle fuel in the state’s Low Carbon Fuel Standard (LCFS) program was negative for the first time in program history.

Carbon intensity (CI) refers to the amount of carbon by weight emitted per unit of energy consumed. A fuel is carbon negative when it takes more carbon out of the environment than it produces.

RNG made up nearly 90% of all natural gas vehicle fuel in the low carbon fuel program and consumed in California in the first half of 2020, up from around 77% in 2019, according to CARB data.

FreightWaves spoke to Gladstein about how the California LCFS program works, the latest carbon negative stats and why the state should dedicate more resources to RNG as a strategy to reduce emissions from the medium- and heavy-duty trucking sector.

Regulations fuel the market

The purpose of California’s low-carbon fuel standard is to compel a 20% reduction in the carbon intensity of transportation fuels used in the state by 2030. 

The vast majority of trucks run on diesel, which has a carbon intensity of slightly over 100 grams. But in 2020 the LCFS target for diesel was 92 grams. “So if I’m a refiner,” Gladstein explained, “and I haven’t done anything to my system, then I am generating a deficit of 8 grams. I need to go out in the marketplace to make that up.”

Fossil fuel natural gas has a CI value of 85, generating 7 grams worth of credits — the difference between 85 and 92 — that producers can sell in the marketplace. 

But by 2030, the cap in California will be around 80. So natural gas producers also have to figure out how to sell a more carbon-friendly product.

Not all renewable natural gas is created equal

Enter RNG, which is produced by capturing and processing the methane (a greenhouse gas) emitted from organic sources including cow manure, wastewater treatment plants, food and green waste, landfills, and forest management.

A so-called drop-in fuel, RNG can be substituted seamlessly for fossil fuel-derived natural gas in the estimated 175,000 natural gas vehicles on the road today — the majority are commercial vehicles in the refuse, transit, and medium- and heavy-duty truck markets.

Each source of RNG has an independent CI value. Wastewater gas averages about 15 grams per megajoule of energy (the standard unit of measurement). Food and green waste lies somewhere between zero and negative 25. 

Then there is the queen of RNG, dairy and swine gas, which clocks in with a negative 300 CI.

It achieves this by capturing methane emitted by cow and hog manure and diverting into fuel, in the process “actually reducing global warming,” Gladstein explained.

More dairy gas — “and a little swine gas” — is coming into the market, he said, offsetting higher CI forms of RNG and pushing the average CI of renewable natural gas in the low carbon fuel program below zero.

During the second quarter of 2020, the average CI of RNG in the LCFS clocked in at negative 0.85 grams, according to CARB. 

Put another way, according to Gladstein, if all the vehicles in California were fueled with RNG at minus 0.85, then that sector would no longer be contributing to climate change.

But is there enough dairy gas to power the medium- and heavy-duty truck sector?

In a word: no. But as Gladstein points out, dairy and swine gas don’t need to dominate the RNG market, because if you mix the latter at negative 300 with landfill and wastewater digestion gas that is in the teens and 40s, you end up with a negative carbon gas supply.

He added that encouraging reutilization of waste as a fuel will encourage economic development and the preservation of family farms now shuttering at an alarming rate.

“Over the past few years, the price of CO2 equivalent in the LCFS market has hovered around $200 per metric ton,” Gladstein observed. “So selling RNG to the medium- and heavy-duty sector is becoming a pretty big and lucrative business.”

The catch: RNG is carbon negative but not zero emission

RNG volumes are increasing and so are the carbon benefits. Casting a pall on that growth, industry advocates say, are public policies that continue to shun RNG in favor of electric-powered truck transportation.

The sticking point revolves around the fact that greenhouse gas emissions aren’t the only pollutant to come out of a tailpipe. Diesel particulate matter (soot) is another one, as are NOx emissions, one of two precursors to smog.

Carbon-negative RNG is zero emission — but only for climate gases, as RNG-powered trucks still produce some NOx and particulate matter.

RNG advocates argue that the volume of NOx produced by the latest generation of natural gas engines is so low as to be insignificant to the formation of smog. “That’s why we call it a ‘near-zero-emissions’ truck,” Gladstein said.

But that logic has yet to make a significant impact on California clean truck policy, much of which is heavily weighted toward electric trucks, which do not produce tailpipe emissions but can generate emissions through the production of electricity at power plants.

Notably: California’s landmark clean truck sales mandate requires manufacturers to sell an increasing number of electric vehicles, with a goal of shifting the state to all electric trucks by midcentury. A growing number of states are looking to enact similar regulations. 

RNG vehicles are locked out of these and similar programs, as are other near zero emission fuels such as propane.

Gladstein finds that irksome. Expressing a widely held view in the natural gas vehicle industry writ large, he said, “California policy is technologically determined rather than performance determined … intent on electrifying the transportation sector no matter what the consequences are in the near term.”

A “more balanced” policy that encouraged increased utilization of natural gas fueled by RNG would deliver significant public health benefits now, he added, “rather than waiting until 2045, the target date for phasing out fossil fuel trucks.”

“I’m not dissing electric trucks — they are incredibly important and necessary technologies,” Gladstein clarified. “It’s a question of when are they going to be available in the numbers that actually make a dent in the medium- and heavy-duty sector. So why not utilize the bird in the hand.”

Beyond California

Whether 2021 will usher in a new era of  low-carbon fuel standards, helping the industry maintain that balance in the near term, remains to be seen.

Outside of California, states are tightening or adopting regulations aimed at decarbonizing transportation fuel. Washington and Oregon already have a low-carbon fuel standard on the books. Colorado and New York are eyeing similar standards, and Canada will implement a nationwide program in 2022. And calls for a nationwide clean fuel standard are expected to intensify under the Biden administration.

In the meantime, more than $1 billion of investment is currently taking place in California to develop a wide array of RNG production projects. Over the past five years, RNG’s use as a transportation fuel in California increased 210%.

Across North America, the RNG industry has developed more projects than it did in its first 30 years in existence, according to the RNG Coalition.

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Linda Baker, Senior Environment and Technology Reporter

Linda Baker is a FreightWaves senior reporter based in Portland, Oregon. Her beat includes autonomous vehicles, the startup scene, clean trucking, and emissions regulations. Please send tips and story ideas to [email protected]