RNG for Transportation Sees Uptick: Part 1

With tightening environmental regulations and a drive to reach corporate sustainability goals, fleet owners are turning to renewable natural gas (RNG).  This two-part series explores benefits of RNG, evolving markets, and evolving engines powered by this low- to zero- carbon fuel.

Part one focuses primarily on activity in California but eludes to trends beyond. In Part 2 David King, product manager Spark Ignited Engines, Cummins, discusses Cummins’ latest model, about to roll to market; he projects what the upgrade could mean for refuse fleets.

California fleets increasingly turn to renewable natural gas (RNG), with consumption climbing 169% over the last five years to 190.46 million gallons, and investments in pipeline-quality RNG projects soaring from a few million dollars to billions in that same window.  With the boom, this biogas-sourced fuel is getting cleaner; fleets have achieved carbon-negativity for three consecutive years.

A bulk of the supply comes from wastewater treatment plants, dairy farms, and landfills who are cleaning and processing methane from decomposing organics, compelled by California’s SB1383 requiring them to capture methane rather than flare it to mitigate climate impact.  Alongside that legislation, California’s low-carbon-fuel standard (LCFS), enabling trading of carbon credits for RNG, is further driving an uptick in projects, notes Tom Swenson, president of the California Natural Gas Vehicle Partnership and Global Regulatory Affairs manager Cummins.

“The low-carbon fuels industry has stepped up and taken advantage of LCFS. It’s a market-based system and super effective at driving down methane and carbon [released into the atmosphere] from various waste streams, especially from dairy, which is very potent,” Swenson says.

Today, the breakdown of RNG by feedstock goes like this, according to RNG Coalition: 5% from wastewater, 6% from food waste, 17% from ag waste, and the lions’ share –72% – from municipal solid waste.

Waste-management operations in particular are not only driving down their emissions but reaping monetary benefits through a circular economy approach. 

“They are using gas to collect waste, then processing the methane from that waste to produce more gas to fuel their trucks. So, they are generating something beneficial they can use and at a lower cost because they are producing it anyway,” Swenson says.

Corporate fleets are buying a bulk of it, particularly large, publicly traded companies with ambitious climate commitments.  In turn, Wall Street and investors have responded, notes Daniel Gage, president NGVAmerica.

Growth in natural gas investments, including renewables, continues in the parcel delivery and short- and long-haul trucking sectors.  And transit authorities are replacing existing natural gas buses with new vehicles or expanding natural gas investments in fleets that run workhorse routes.

While California leads in advancing RNG – it accounted for 97% of fuel in natural gas vehicles in 2022 – other states are following suit.  Oregon, Washington, and Canadian regions have adopted their own low-carbon fuel standards, and others are considering it, which will continue to stoke RNG demand, projects RNG Coalition.

The U.S. Environmental Protection Agency’s latest Renewable Fuel Standard update indicates further growth; the program mandates production of 840 million gallons of cellulosic biofuel volumes for 2023, which will increase incrementally to 1.38 billion gallons for 2025.

The industry is preparing by building out infrastructure, opening dozens of stations each year, including private stations and expansion of the public access network (such as truck stop locations), and over 100 stations are in the pipeline, says Chad Lindholm, Clean Energy senior vice president. The corporation, North America’s largest provider of RNG for transportation, currently has 600 public and private sites in operation.

In California alone, over 200 fueling stations supply natural gas, including RNG, to heavy-duty trucks in refuse, transit, trucking, and airport spaces.

There’s big potential to scale beyond nationwide.

“[Extensive] pipeline infrastructure is already there. So, once you determine where you will make that investment, you can build out RNG plants and inject into the closet pipeline, with access to millions of miles of infrastructure, which allows you to generate a certified pathway to any one of these facilities,” Lindholm says.

As with the gas and infrastructure, the engines are evolving too. Cummins, the only manufacturer of heavy-duty natural gas engines, builds 8,000 of them a year for U.S. fleets, most which run on California roads.

In California, natural gas has been the predominant fuel choice for years, achieving significant reductions in criteria pollutants (NOx and particulate matter). But it was just with the introduction of RNG that the engines began addressing carbon emissions.

Since then, Lindholm notes, demand is mounting, primarily for larger horsepower engines, especially in refuse. Lately operators are beginning to power their roll-off trucks and transfer trucks with RNG.

Cummins is about to roll out its next-generation platform, a 15-liter engine. It’s 300 pounds lighter than the 12-liter and will have more power, equating to a greater payload. Swenson estimates fuel economy will improve by 15%.

While electric vehicle technology advances, it continues posing limitations for certain sectors, and RNG will make more sense for them, attests Gage, who points to vocational, construction, and freight applications, which he says will be “virtually impossible to electrify.”

Any duty cycle or application that runs 24/7, requires extended range, or needs the greatest weight and payload capacity will find battery electricity too limiting. 

Natural gas is the ultimate alternative fuel technology that accommodates these operations’ existing business models, he contends.

What does the future look like on the clean transportation fuel front?

Some industry experts project more engines and products that will run on more gaseous fuel types, including hydrogen. 

“We also see electrified trucks where a natural gas gen-set powers and recharges the battery pack to greatly extend range and mobility,” Gage says.

Additionally, he says many new technologies are poised for commercial deployment in 2024, ranging from traditional internal combustion engines to adsorbed natural gas technologies to hybrids.