Natural gas engines: Questions answered

Natural gas engines: Questions answered

When it comes to natural gas engines, there are a range of frequently asked questions about the cost, practicality, and feasibility of integrating natural gas into commercial fleets. There are certainly preparations that need to be considered, but the learning curve to implement natural gas engines is not as steep as people may think, especially in comparison to the benefits of natural gas in transportation applications.

In this article we’ll answer some of the most frequently asked questions when it comes to adding natural gas engines to your commercial vehicle fleet.

Can a diesel engine run on natural gas?

The short answer is no. If you fueled a diesel engine with natural gas it simply wouldn’t start. Diesel engines can’t run on natural gas because natural gas combustion requires spark plugs. Diesel engines cause fuel to ignite through compression. To self-ignite, natural gas would need to be compressed at a ratio far greater than what internal combustion engines can apply.

However, there are specially modified engines which can run on either diesel or natural gas. Vehicles with this type of engine, which are known as bi-fuel or dual fuel engines, feature two fuel systems and can switch between one fuel and another as needed. For example, if their compressed natural gas (CNG) cylinder runs out and there is no CNG station nearby, operators can simply flip a switch and keep driving on diesel. There are also engines which use diesel and natural gas at the same time. In these engines, diesel provides ignition and natural gas provides power. Such engines are especially popular in stationary oil and gas drilling applications. If natural gas is being extracted, it can be used to fuel the engines. If no natural gas is available, the engines can revert to using diesel. The Cummins QSK 50 engine, for example, is a popular dual fuel engine commonly used in oil and gas applications.

Can a natural gas engine run on renewable natural gas?

Absolutely! The option to run on renewable natural gas (RNG) is a big reason fleets switch to natural gas vehicles. While virgin natural gas has many sustainability benefits, including 13% – 17% lower well-to-wheel greenhouse gas (GHG) emissions and 27% lower CO2 emissions than petroleum. But the environmental benefits really shine when using RNG made with biogas.

For fuels beyond RNG, you can learn more on how natural gas compares to LPG, LNG, and diesel here.

What are the environmental benefits of RNG?

Depending on the energy source, the carbon intensity of renewable natural gas can be neutral or even sub-zero. How is that even possible, you might ask?

It’s because the main elements of RNG come from biogas, which is the fermentation of organic waste in places like landfills, wastewater treatment facilities, or industrial agriculture waste digesters. Biogas like methane is captured during this treatment process, preventing it from ever being emitted into the atmosphere. This carbon intensity score factors into the total well-to-wheel emissions calculation of the vehicle.

Refined biogas is functionally indistinguishable from fossil natural gas and can be used as a natural gas substitute. If interested, learn more about the production and processing of biogas, natural gas, and other low carbon fuels.

Is it cheaper to run natural gas engines?

Most of the time, yes. Natural gas vehicles require less maintenance than diesel vehicles equipped with post combustion exhaust treatment systems. They also result in significantly lower fuel costs. In the United States, the average retail fuel price has been significantly lower than the average retail price of both gasoline and diesel for more than 20 years. Retail natural gas prices are also more stable than the price of other fossil fuels.

Payback on a natural gas vehicle is dependent on several factors, including the specific application, duty-cycle, number of miles driven per year and the cost of fuel compared to diesel. But by most metrics, natural gas delivers a lower total cost of operation than diesel.

click to view infographic
Click to view infographic

Do natural gas engines start better than diesel engines in cold weather?

No engine is completely immune to cold-weather challenges. Some issues are common to most vehicles, including those using an internal combustion engine. One issue natural gas engines sometimes experience in freezing weather is a loss of power by the battery. There are also potential issues specific to the use of natural gas. For example, the O-rings in the fueling receptacle can become frozen, preventing the fuel nozzle from coupling correctly with the receptacle.

There are two cold weather difficulties that diesel drivers face, which natural gas drivers will never experience. The first is, unlike diesel, natural gas does not turn to gel when it is cold. Regardless of temperature, natural gas is entirely gaseous when it enters the engine. Methane, the main constituent of natural gas, has a boiling point of -258°F, or -161 °C.

The other difficulty is caused by the diesel exhaust fluid, or DEF, in diesel vehicles. DEF largely consists of water and can easily freeze. Storing and handling DEF in cold weather can be challenging. Because natural gas burns cleanly and with minimal NOx (nitrogen oxides) formation, natural gas vehicles have no need for heavy-duty DEF-consuming NOx scrubbers. As a result, DEF and DEF-related problems are unknown to natural gas vehicle drivers.

Who makes natural gas engines?

Cummins Inc. and several other manufacturers of heavy and medium-duty engines have an extensive portfolio of natural gas engines suitable for a large variety of on-road, off-road and stationary applications. Most truck and bus makers have product lines featuring natural gas engines, so businesses interested in exploring natural gas options can usually do so with their preferred truck maker. Learn more about Cummins’ full line of natural gas engines.

Puneet Singh Jhawar

Puneet Singh Jhawar

Puneet Singh Jhawar is the General Manager of the global natural gas business for Cummins Inc. In this role, he is responsible for the product vision, financial management and overall performance of the natural gas business. Over his 14-year career at Cummins, Jhawar has cultivated successful relationships with a number of Cummins’ largest customers. Jhawar has extensive global experience, with roles based in the Middle East, India, Europe and the US.

Cummins Custompaks are being used for water management as Thailand struggles with its water crisis

CustomPak on site

Water crisis

Sixty Cummins Inc. CustomPaks are in service in Thailand as part of a critical water management plan aimed at easing the country’s water crisis – a crisis that has caused enormous economic and social damage and stirred conflict among communities.

Over the past several decades, Thailand has continually faced water problems caused by severe drought. Water reserves in dams and reservoirs are insufficient while water resources are often contaminated with toxins caused by urban communities and the industrial and agricultural sectors.

Severe flooding is a threat, too, at a time when the realities of climate change are hanging over the country.

As a result, the allocation of precious water resources, which must be shared among various stakeholders including new and existing industry, large and small agriculture, and cities and villages has become a flashpoint.

Kittithanapat Engineering Co. (KTP), has been involved in the water management system since 1996, working closely with authorities such as the Royal Irrigation Department, Department of Water Resources, Bangkok Metropolitan Authority and others.

CustomPaks on site

600 hp CustomPaks

To help KTP meet its often urgent requirements, Cummins DKSH (Thailand) has recently supplied 60 Australian-built CustomPaks – 45 powered by Cummins’ X15 engine rated at 600 hp, and 15 powered by the QSL9 rated at 325 hp. These fully self-contained powerpacks are emissions certified to Tier 3.

The CustomPaks are coupled to hydraulically-driven, large-volume submersible water pumps sourced by KTP from US company Moving Water Industries (MWI); KTP is the exclusive distributor in Thailand for these MWI Hydroflo pumps.

Prior to Cummins’ involvement, KTP was using another diesel engine brand but service support wasn’t up to the standard required.

Long-serving KTP engineer Kittisak Thanasoot says Cummins DKSH’s reputation for technical and aftersales support along with the reliability of the Cummins product were a key reason behind KTP’s decision to specify the CustomPaks for the Royal Irrigation Department.

The ability of Cummins DKSH to respond to short delivery times was also important.

“Supplying large quantities of high horsepower diesel engines for emergency situations such as flash flooding can be a challenge for KTP,” says Kittisak Thanasoot.

“Responding to the needs of the government agencies to manage such problems in a timely manner and with least impact on communities, KTP has found the answer in our partnership with Cummins DKSH.”

Power, pride and passion

Parked semi truck

The switch back to Cummins power has been beneficial for iconic New Zealand company Uhlenberg Haulage. It's all about whole-of-life costs.

Uhlenberg Haulage is closing in on 60 years in business, having been founded in 1966 by Mike and Carol Uhlenberg.

Based in Eltham, Taranaki, in New Zealand’s North Island, the operation is today owned and operated by their sons Chris, Daryl and Tony Uhlenberg.

Describing the Uhlenbergs as “old school family truckies”, Daryl talks about the company’s time-honored journey with a definite tone of pride, especially the work of his parents in laying the foundations for what is today an iconic fleet in its own right.

Cummins Inc. made its debut in the Uhlenberg fleet in 1971 with an NH250 powering a second-hand Kenworth K923 used in logging. A second Kenworth, a new W924 with a Cummins NTC335, followed soon after hauling an LPG tanker.

The Uhlenberg operation today comprises 40 prime movers and a variety of trailing gear to cater for the myriad of a jobs the fleet is involved in.

A number of Peterbilts feature in the fleet although Kenworth is now the brand of choice with six new units to be delivered over the next 12 months to cater for business growth.

Cummins’ X15 Euro 5 engine rated at 550 or 600 hp is the preferred power specification, with 18 red engines currently in the fleet.

Uhlenberg family in front of truck

Whole-of-life support

“The switch to Cummins has been a very good experience for us. We have nothing but praise for the Cummins organization,” says Daryl.

“The whole-of-life picture is the key thing for us and we’ve got that nailed with the support we get from Cummins – parts availability, scheduled maintenance, life expectancy and in-frame rebuilds.

“So the red engines turn up, we run them to life, which is 900,000 to 1.2 million kilometers, and then Cummins does an in-frame overhaul in a timely manner. If there’s an issue, parts and support are close by.

“The support we get from Cummins Palmerston North is fantastic, second to none.”

Daryl recently looked under a Kenworth that was in the workshop for a service and was surprised to see no oil leaking from the one-million-kilometer X15. “I remember when I was a fitter we had to wear a raincoat when working under a truck,” he jokes.

Fuel agnostic

Acknowledging that the push to decarbonize is now “very real”, Daryl likes the idea of Cummins’ fuel agnostic concept where one base internal combustion engine, optimized to run on diesel, can also be customized to run on ultra-low and zero-carbon fuels like renewable natural gas and hydrogen.

“My father was a pioneer of linehaul trucking in New Zealand and he always embraced new technology. He was never scared of it,” he says.

“I tend to be a little more cautious but I can see where a 500 hp natural gas or hydrogen engine would work for us in short haul applications,” he admits. “We’re certainly willing to look closely at these alternative fuel technologies when suitable infrastructure is in place.”

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