Natural gas engines vs. diesel engines

Natural gas fueling station

From tractor trailers and transit buses to delivery trucks and terminal tractors, fleets have traditionally relied on diesel engines to provide the torque, reliability and durability needed by heavy-duty commercial applications. Natural gas engines, however, have emerged as a great alternative to diesel. Drivers, mechanics, and fleet managers appreciate natural gas engines for a variety of reasons.

Drivers find that natural gas engines have similar performance and drivability as diesel engines. The leading difference between natural gas and diesel engines is noise; natural gas engines are quieter.

Natural gas offers convenient refueling options

Natural gas also improves the refueling experience for many fleet drivers. In a world of several alternative fuel options for commercial vehicles ranging from natural gas to liquified petroleum gas (LPG); natural gas can be used in a vehicle in either compressed or liquefied form. For fleets with behind the fence refueling capability, natural gas refueling stations can be set up on site to ensure that each vehicle has a dedicated fuel hose. There are two basic types of fueling equipment: fast-fill and time-fill.

Fast-fill systems combine a compressor and a high-pressure storage system. The storage system, called a cascade, fills the vehicle's fuel tank in about the same time it takes to fuel a diesel vehicle. Compressed natural gas can’t spill during refueling and drivers never go home smelling of diesel.

Time-fill systems don’t have a storage system and typically compress the gas directly into the vehicle storage cylinders to refuel vehicles while they’re parked overnight. With time-fill systems, drivers pull into their designated space at the end of their shift, connect a fuel hose to their vehicle’s natural gas cylinder and go home. Drivers don’t need to wait for their turn at the diesel pump and don’t need to wait again until their tank is full. This saves them time and saves their company money.

Natural gas exhaust systems are cheaper and easier to maintain than diesel aftertreatment systems

There are no complicated exhaust gas aftertreatment systems on natural gas vehicles. Modern diesel trucks require a set of sensors, filters and converters to scrub pollutants such as nitrogen oxides and soot from their exhaust. Some converters consume diesel exhaust fluid, or DEF, a water-based reagent whose handling can be challenging in cold weather. Natural gas burns much cleaner than diesel, so few or none of these systems are required on a natural gas vehicle. All of the exhaust is run through a simple three-way catalyst, resulting in near zero NOx levels (0.02 g/bhp-hr NOx).

It is important to closely follow recommended maintenance intervals with natural gas engines, but with proper maintenance, it’s not uncommon for natural gas trucks to reach a million miles. And mechanics often find that maintaining a natural gas engine can be a more pleasant experience because of how clean they are.

Natural gas promotes cost savings

Besides enjoying savings in terms of lower maintenance costs and reduced maintenance downtime, fleet managers can also save big on fuel costs. In the United States, the retail price of compressed natural gas has been consistently lower than the price of diesel since the start of the shale gas boom in the early 2000s. It is also decoupled from the price of oil, and therefore has been quite stable. As a result, natural gas fleet operators don’t experience wild swings in fuel prices that other fleets must deal with whenever oil prices rise and the cost of diesel jumps. This comes in addition to all the other benefits natural gas engines offer for transportation applications.

Natural gas cuts greenhouse gas emissions

Natural gas has many sustainability benefits, including 13% – 17% lower well-to-wheel greenhouse gas (GHG) emissions and 27% lower CO2 emissions than petroleum when using virgin natural gas. The benefits really shine when using renewable natural gas (RNG) made with biogas.

 

RNG can help fleets reach sub-zero GHG emission levels because producing RNG captures biogas like methane that would have otherwise been emitted into the atmosphere through natural decomposition. This biogas comes from the fermentation of organic waste such as animal manure in industrial digesters. Switching to renewable natural gas can be an effective way for these businesses to reach any greenhouse gas reduction objectives they may have. Many transportation businesses operating in agricultural areas have found ways to create win-win partnerships with local farmers willing to invest in a renewable gas production setup. Municipalities and refuse companies that own landfills are able to capture methane generated through waste decomposition and sell that to the RNG fuel producers, essentially offsetting their fuel costs.

If natural gas engines are relevant to your needs, don’t forget to also check our answers to frequently asked questions about natural gas engines. These answers cover topics such as cost, practicality, and feasibility of integrating natural gas into commercial fleets.

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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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