New ways to power off-road machines, which mostly run on diesel, could cut about 3 percent of U.S. carbon emissions.
SHIPPENSBURG, Pa. — On a 40-acre dirt and gravel lot, I climbed into the cabin of a 55,000-pound excavator. Construction crews use these hulking machines to dig trenches for laying pipes and wires or hollowing out building foundations. I took it out for a joyride. Hitachi Excavator
When I switched on the motor, there was no ignition roar and no belch of diesel fumes from a tailpipe. This machine, powered by four batteries that each are big enough to run a small electric car, came to life silently.
The quiet didn’t last. The excavator’s giant treads trundled noisily over the gravel until I reached a good spot to dig. Then I grabbed hold of two joysticks and sank the bucket arm down into the dirt to scoop out as much earth as the claw could carry. I hit a big rock. The machine momentarily pitched forward, straining to loosen it from the ground — and then the electric motor heaved the boulder and a clod of dirt into the air in a puff of dust.
When they run on diesel, the biggest pieces of construction equipment can churn through 10 or more gallons of fuel per hour, emitting as much carbon and air pollution as several cars combined. Off-road equipment, including excavators, bulldozers, cranes and tractors, creates about 3 percent of U.S. carbon emissions — roughly the same as the airline industry. Making these machines carbon-free would be almost as big a step toward halting climate change as taking all commercial planes out of the sky.
It won’t be easy. Electrifying off-road vehicles presents all the same challenges as replacing gas-powered cars with EVs, including worries about charging infrastructure, battery capacity and high upfront costs — plus the added challenge of digging, pushing and lifting heavy loads for hours at a time.
“They are more difficult because most of these vehicles don’t just propel themselves; they also do work,” said Kim Stelson, a mechanical engineering professor at the University of Minnesota who studies off-road vehicles. “But if we want to solve the overall problem [of climate change], we have to solve this one.”
Despite the obstacles, electric machines are slowly starting to show up at farms and construction sites. John Deere plans to sell more than 20 models of electric and hybrid construction equipment and tractors by 2026. Construction giants Caterpillar and Komatsu are developing electric excavators and wheel loaders. Volvo Construction Equipment, which made the excavator I was driving, sells seven electric models. “Almost all the major companies are working on electric solutions,” Stelson said.
Volvo’s electric machines are very similar to its diesel machines, with the exception that their engines have been swapped out for batteries. The 55,000-pound electric excavator, for instance, has 264 kilowatt-hours of battery storage — the same as nine Mini Cooper EVs, or a little more than one electric Hummer.
I drove both the electric and diesel versions of the machine, and the differences between them mirrored the differences between EVs and gas-powered cars. The electric machine idled silently and its controls were slightly more responsive than the diesel one, because its electric motor can deliver power faster than a combustion engine — similar to the way an EV can accelerate faster than a gas-powered car. But both machines pulled dirt out of the ground with the same power.
You can see the similarities on display on the assembly line at Volvo Construction Equipment’s North American headquarters in Shippensburg. Similar hulking, half-formed chassis move down the lines for both types of vehicles. But, halfway through, a huge hook hanging from the ceiling will either lower an engine or a battery pack into the machine for workers to install.
The electric machines are catching on slowly. Of the 60,000 pieces of construction equipment Volvo delivered to customers last year, 895 were electric according to the company’s annual report. The company said it aims to offer electric versions of more than a third of its models by 2030.
Electric machines are good for a particular kind of job site. The machines need a place to charge — which could be the same level 1, 2 or 3 chargers that EVs plug into in buildings, parking lots or charging stations. And ideally, they wouldn’t have to move heavy loads for very long shifts.
“If you have a 24-hour, round-the-clock type of [work schedule], battery electrics aren’t very practical because you can’t stop to plug in for the four or five hours that it would take to recharge it,” said Ray Gallant, vice president of sustainability and productivity services at Volvo Construction Equipment.
Volvo says it often sells or leases electric machines for job sites where it pays to limit noise and air pollution. The Toronto Zoo used one of the company’s machines to avoid upsetting animals while repairing their enclosures. Cemeteries have bought excavators to quietly dig graves without disturbing mourners. Construction crews working on busy city streets use the machines to avoid annoying the neighbors or polluting their air.
At the Molly Pitcher dairy farm five miles down the road from Volvo Construction Equipment, farmers use an electric wheel loader to move feed, clean out barn floors and help lift and maintain pumps. The farmers say it’s better for the cattle to be around quieter machinery. Plus, they can charge the battery free because the farm generates its own electricity using a device that converts manure into power.
“The more I can use that electricity, the more profitable we are,” said Keith Jones, the farm owner.
On other job sites where electric vehicles aren’t practical, construction crews can cut their emissions by running their machines on greener fuels, such as renewable diesel made from crops or used cooking oil. California now requires all off-road equipment to run on renewable diesel.
“There, you’re getting up to a 70 percent carbon benefit relative to running a diesel fuel, so that could be a really key intermediate step,” said Tom Durbin, a faculty researcher at the Center for Environmental Research and Technology at the University of California, Riverside.
One day, crews could upgrade to machines that run on pure hydrogen, a fuel that creates zero carbon emissions — but those mainly exist as prototypes today.
Shantui Wheel Loader A previous version of this article included a photo of a diesel excavator incorrectly described as an electric excavator. The photo has been replaced.