Cargo transportation companies are replacing diesel-powered generators with units fueled by solar, batteries and regenerative brake energy in an effort to cut emissions from refrigerated containers and trucks that carry produce, frozen food, pharmaceuticals and other goods.

Goods moved through the cold supply chain typically are kept at low temperatures by refrigeration systems, known as Transport Refrigeration Units (TRU), that are powered by diesel engines. Although the engines are small, typically 9 to 36 horsepower, their emissions are amplified by the gathering of similar trailers and vehicles at distribution centers, truck stops and other facilities with their cooling systems running.

The shift from diesel to renewable energy is part of the multi-pronged effort by cold goods trucking and logistics companies to cut emissions and reduce the waste of food spoiled in transit, according to speakers at an online Net-Zero Carbon Summit Sept. 18 organized by FreightWaves, a logistics and trucking website. As well as reducing diesel use, the methods include improving supply chain efficiency and reducing energy use through more efficient temperature control systems that can minimize the amount of food that goes bad en route.

The focus on cutting TRU emissions is seen in the industry as a solid — and cheaper — first step toward the far more expensive decision to replace diesel-powered trucks with vehicles powered by electricity or other renewable energy.

“TRUs are generally dirtier than trucks,” said Lynda Lambert, a spokeswoman for the California Air Resources Board (CARB). The agency, which has regulated TRUs since 2004, enacted rules in 2022 that will require all of the 200,000 truck-based TRUs in the state to be emissions free by 2030 and sets tight emissions standards for refrigerated containers.

“TRUs are often clustered at facilities located in some of the state’s most vulnerable, overburdened communities that suffer from poor air quality,” Lambert said, in an email interview with Net Zero Insider. “These communities located near main goods movement hubs like ports, railyards and warehouses bear a disproportionate health burden from the emissions.”

Speaking at the conference, Robert Koelsch, CEO of AEM, of Mesa, Arizona, which manufactures solar-powered TRUs, said powering a TRU with renewable energy instead of diesel could save 27 tons of carbon emissions a year.

“That’s a lot, and much easier to implement than a (truck) tractor,” he said. “So we would advise people to look at your TRU fleet first before you look at tractors.” The company website says its refrigerated containers have saved more than 2,000 tons of carbon emissions on more than 1 million deliveries, and compares the zero emissions from its units to typical units that generate between 16.5 and 33 tons of carbon a year.

Koelsch said he began looking to cut TRU emissions 15 years ago when he first encountered a diesel-fueled refrigerator that “started up and the front of the unit shook and smoke, black smoke came out of the top of it.” His company within six months developed a unit fueled by solar-generated electricity stored in a 5,000-pound forklift battery, he said.

The company then worked to retrofit diesel units to run off solar panels on the roof of the container and created a generator to convert energy from the truck wheels into electricity, he said.

“The idea was to go 100% zero emission, not hybrid; no diesel backup,” he said. “We have a patented wheel generator that gives you a range extension on the road in California.” The company also has focused on increasing the efficiency of the cooling unit so that it runs on less energy, and so uses less battery charge, he said.

Hybrid Solution

Paul Kroes, trailer innovation leader at Thermo King, of Minneapolis, which manufactures refrigerated trailers, trucks and vans, said the sector is shifting from diesel-fueled refrigerators to hybrids of electricity and diesel for the same reason consumers have turned to hybrid EVs.

“Range anxiety is a real thing,” he said, and the consequences are greater for an electric refrigeration unit. “For example: Am I going to make it through the day with my load cold? And that’s arguably a much bigger deal and a much more expensive problem.”

Thermo King manufactures electric TRUs for smaller trucks and vans and electric battery packs, and it is set to launch another hybrid unit that runs on diesel and “shore power,” or plug-in electric when the unit is parked at a warehouse or a dock. The company says it is spending $100 million to introduce all-electric transport refrigeration systems “across the global transport cold-chain” by 2025, and in May said it had partnered with Range Energy, a manufacturer of heavy duty trailers, to develop an electric refrigerated trailer, following pilot tests of hybrid units on trailers.

Hybrid refrigeration solutions are growing more popular, Kroes said, because they allow “fleets to dip their toes or their ankles or up to their knees into the EV space.” Companies that ship temperature-controlled goods can go some way to “decarbonizing their fleet without ultimately risking load losses and operational disruptions that can have big impacts, not just to their bottom line, but to their customers and ultimately to us as consumers.”

Still, Kroes said he expects the use of hybrid models to be a short-term solution.

“After a few years, I would hope that fleets start to notice they’re using that engine less and less as a training wheel and eventually they take the training wheels off and they go to an all-electric,” he said. “So hybridization is definitely an interim step.”

Damaged Food Loss

Emissions reductions also can be achieved by simply cutting the amount of food that is damaged or destroyed en route to its destination, and so eradicating the need to produce and ship it needlessly in the first place, speakers said. That approach was highlighted in a recent study by the University of Michigan that found half the food wasted globally could be eliminated through the use of full refrigerated food supply chains, which in turn would cut greenhouse gas (GHG) emissions by 41%.

“The common thread is that if you optimize the cold chain, you’re going to see a reduction in product loss,” said Ilya Preston, CEO of Paxafe, which helps clients improve the efficiency of their supply chains through data collection and analysis. “You’re going to see, therefore, reductions in greenhouse gas emissions.”

But the scale of the emissions reductions can depend on what products in the cold supply chain are the focus of efficiency efforts, he said.

“Meat, for example, accounts for 10% of global loss, but it accounts, on the flip side, for 50% of total greenhouse gas emissions,” he said. “So yeah, I could invest into reducing the loss rates of meat. I’m not going to get that much of a return on the actual quantity of meat that I save. But I’m going to get a ton (of emissions reductions) environmentally speaking.”

“Whereas fruits and vegetables, they make up 30% of the volume of loss in terms of in terms of food, but they only account for 9% of the emissions gases,” he said.

Evigence, of Hoboken, N.J., makes sensors that monitor in real time the freshness of food under transportation in the cold supply chain, Oria Malka, vice president of sales, said at the conference. The sensors use a chemical process “that basically mimics the degradation of any perishable product,” or the freshness, she said. And the company then uses AI to analyze the data to help customers pursue a “smarter decision-making process, using that data to kind of drive less waste, prevent waste in their supply chain, and also optimize their supply chain.”

“And by doing that, you can optimize that shelf life later on in your supply chain and basically not throw that product” out, she said. That enables customers to “optimize those processes and reduce packaging materials, installation materials, and identify where you can go toward more efficient production lines or routes within your cold chain,” she said. “And by that reduce those carbon footprints, and basically make yourself more of a sustainable company.”