With tightening environmental regulations and a drive to reach corporate sustainability goals, fleet owners are turning to renewable natural gas (RNG). In Part 2 David King, product manager Spark Ignited Engines, Cummins, discusses Cummins’ latest model, soon to roll to market; he projects what the upgrade could mean for refuse fleets.

Arlene Karidis, Freelance writer

July 25, 2023

8 Min Read
rng trash
Kathy deWitt / Alamy Stock Photo

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, soon to roll to market; he projects what the upgrade could mean for refuse fleets.

Waste360: What are main benefits of renewable natural gas (RNG)?

King: Natural gas, no matter its origin source, provides a significant reduction of nitrogen oxides (NOx) emissions at the tail pipe. But in recent years we’ve seen many fleets moving from geologic, or virgin natural gas, to RNG because of the decarbonization advantages.

Virgin natural gas is a fossil fuel, but still offers carbon intensity benefits over diesel. But the environmental benefits really shine when using RNG, made with biogas, offering carbon intensity that can be neutral, or even below-zero, depending on the energy source.

Waste360: Describe the evolution of Cummins’ natural gas engines

King: Cummins introduced the first natural gas engine for the commercial vehicle segment in the 1980’s with the introduction of the L10G. Since then, Cummins has produced nearly 80,000 natural gas engines for use in North America.

The first market to see significant adoption of the L10 was the transit bus market, with California leading the way. Since then, we’ve seen the list of applications using natural gas expand into refuse trucks and other vocational truck and regional haul applications.

The current line-up ranges from 6.7-liter to 12-liter displacement. The upcoming X15N will expand that range with the introduction of the market’s first 15-liter big bore natural gas engine designed to meet the demands of North America’s heavy-duty segment.

Waste360: What should fleet operators know about Cummins’ upcoming, next-generation option?

King: The Cummins X15N is integrated with the Eaton-Cummins Endurant HD-N transmission and the Allison 4000 transmission. It is 500 pounds lighter than the 15L diesel engines yet provides 15L-diesel- like power and torque. Additionally, it provides near-zero NOx and particulate matter emissions, the low-carbon advantages of CNG, and significant decarbonization that RNG can bring with the potential of net carbon negative.

The torque curve for the X15N’s 500 hp, 1,850 pound-feet rating is very close to that of the X15 diesel — putting out about 1,800 pound-feet at 1,000 RPM and getting to the peak rating by 1,100 RPM. That’s quite a feat of engineering with this type of combustion system.

Waste360: What has been the industry’s response to the X15N?

King: Since we announced the release of the X15N, many of the largest fleets in North America have expressed great interest in the product and the opportunities to decarbonize their fleets with RNG at scale in the very near term.  With the launch of the X15N, Cummins expects the heavy-duty natural gas market to grow to 10% in the next few years.

Waste360: What fuels can you run in the X15N? And what will this flexibility allow?

King: The X15N is the first heavy-duty engine to feature Cummins new fuel-agnostic engine design. This global platform supports natural gas, diesel and, in the future, hydrogen. These engines will have a high degree of parts commonality (similar engine footprints, diagnostics, and service intervals) and reduce adoption costs across multiple fuel types.

It also means easier integration of fuel types across the same truck chassis. Fleets will see lower costs to train technicians and retool service locations compared to emerging technology types such as battery electric vehicles (BEVs) or fuel cell trucks.

Waste360: How does fueling time and driving range compare to diesel?

King: When using fast fill, the fueling time is similar to a diesel truck, allowing for multishift or slip seat operation. We believe vehicle ranges of up to 1,200 miles are possible with the appropriate fuel delivery system on the truck. Many of our field test units are running with the Cummins Clean Fuel Technologies back-of-cab systems with either 135- or 175-diesel gallon equivalent capacity.  More capacity is possible if the fleet operation requires it.

Waste360: At what stage of testing are you?

King: The X15N is currently in field test in North America accumulating miles and hours in a multitude of conditions and locations, in addition to countless hours of engine dyno test cell and rig testing.

Many units are running in regional haul, line haul, bulk haul, and vocational operations. We have active test programs with Walmart and Werner Enterprises, but we have test programs with several other large fleets.

More units will be entering field test over the next few months, including in refuse applications. 

Waste360: When do you plan to roll the X15N to market, and who will offer it?

King: Cummins is planning engine production capability for early 2024. Original equipment manufacturer (OEM) specific launch plans would have to be addressed by the individual OEMs. Cummins can say that PACCAR has publicly announced that the Kenworth and Peterbilt brands will both offer the X15N.

Waste360: What industries are expressing most interest in the X15N engine?

King: Cummins has seen great interest from the earlier adopters of natural gas with the L9N and ISX12N fleets as well as with traditional diesel-only customers. The interest is fueled by a couple of major factors: the stable low cost of CNG as a transportation fuel as well as the decarbonization benefits of RNG and environmental, social, and governance (ESG) targets of carriers and shippers.

Many major companies that have internal or have made external decarbonization targets are recognizing the ability to begin moving more quickly on their journey by moving to RNG as a transportation fuel. This may be of their own fleet or, in some cases, in choosing the carrier they select to move their products. 

Waste360: What advancements have been made in general in RNG engine technology?

King: The platforms and technologies have evolved over time, and we’ve learned a lot about how these engines perform in both the applications (medium-duty, transit bus, vocational, and heavy-duty) and the markets they serve (North America, Asia, and Europe). This experiential learning fueled the design of the X15N.

Our customers aren’t shy about letting us know what aspects of the engines work well and what can be improved. The X15N features design improvements to areas like the power cylinder, pistons, and ignition, injection and fuel control systems. We’ve improved the cylinder head, spark plugs, turbocharger, and block design. We’ve also added a high-capacity oil pan to allow for longer oil drain intervals.

Waste360: How are these trucks built specifically for refuse fleets?

King: Refuse has been a key market for natural gas engines, specifically the L9N and the ISX12N. These engines serve the market in collection, transfer, and roll off applications. 

Refuse and landfills are the intersection where RNG shines. Landfill gases create methane that can be captured and refined into RNG. The RNG then comes full circle to power the equipment to collect and manage waste streams. All while also reducing the harmful greenhouse gas impact of fugitive methane being released to the atmosphere, or having to be flared, losing the work it can do.

Only a fraction of the landfills in our country are producing pipeline- grade RNG. There is a big opportunity to build out this renewable fuel source and grow the landfill RNG supply and use it to displace diesel in commercial transportation. Waste Management (WM) is a leader in this space.  They recently opened a $35 million RNG facility at their Eco Vista landfill near Springdale, Texas. WM plans about 20 additional RNG projects and intends to spend about $1.2 billion on renewable energy projects between 2022 and 2026.

Waste360: What advancements do you see in the pipeline?

King: The future is very exciting for internal combustion engines, which continue to get cleaner and more efficient.

As I mentioned, Cummins recently introduced its fuel-agnostic approach to engine design. We are bringing three new engine platforms to the market over the next three years. Each new platform will have variations for different fuel types appropriate for each market to include natural gas, gasoline, propane, hydrogen, and advanced diesel. 

Cummins is also investing heavily in BEV and hydrogen fuel cell power trains with our Accelera business unit. The Accelera name was introduced earlier this year, covering what was known as our New Power business segment.

With respect to RNG production, investments continue to grow across landfill, wastewater, and dairy gas feedstocks. These investments are coming from many sources, including large energy companies. In addition, there is a large investment from the fueling and energy companies to build out fueling infrastructure, both public and private.

About the Author(s)

Arlene Karidis

Freelance writer, Waste360

Arlene Karidis has 30 years’ cumulative experience reporting on health and environmental topics for B2B and consumer publications of a global, national and/or regional reach, including Waste360, Washington Post, The Atlantic, Huffington Post, Baltimore Sun and lifestyle and parenting magazines. In between her assignments, Arlene does yoga, Pilates, takes long walks, and works her body in other ways that won’t bang up her somewhat challenged knees; drinks wine;  hangs with her family and other good friends and on really slow weekends, entertains herself watching her cat get happy on catnip and play with new toys.

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