Shipping trucks like 18-wheelers are crucial to logistics on a global scale. But they also account for a big portion of the greenhouse gas emissions helping to accelerate climate change.

Developing more efficient vehicles may be key to eliminating net greenhouse gas emissions and curbing pollution. MIT has developed a new concept plug-in hybrid engine system where the truck would be primarily powered by batteries, but with a spark ignition engine. This would allow trucks to travel the same distances as conventional diesel trucks, but using a flex-fuel model running on pure gasoline, pure alcohol or blends of these fuels.

The ultimate goal would be to power trucks entirely with batteries, along with the long-term goal of autonomous trucks being a key to solving first-mile logistics. But the flex-fuel hybrid option could provide a way for such trucks to gain early entry into the marketplace by overcoming concerns about limited range, cost or need for excessive battery weight for longer range.

“We’ve been working for a number of years on ways to make engines for cars and trucks cleaner and more efficient, and we’ve been particularly interested in what you can do with spark ignition [as opposed to the compression ignition used in diesels], because it’s intrinsically much cleaner,” said Daniel Cohn, research scientist at MIT’s Energy Initiative and the Plasma Fusion and Science Center.

Compared to a diesel engine vehicle, a gasoline-powered vehicle produces only a tenth as much nitrogen oxide (NOx) pollution. Additionally, the flex-fuel configuration allows it to run on gasoline, ethanol, methanol or blends of these that emit far less greenhouse gas than pure gasoline engines do and the fuel cost is small as well, researchers said.

If the fuel is pure methanol or ethanol from renewable sources such as agricultural waste or municipal trash, the net greenhouse gas emissions could even be zero.

Cohn said that while all-electric heavy-duty trucks— such as the ones being developed by Tesla Motors, TuSimple and Ike — will be important, it will be a challenge because of the cost and weight of the batteries to meet sufficient range.

This hybrid model is a first step toward improved fuel-efficiency, producing a tenth as much air pollution as the best of today’s diesel-powered vehicles.

“Batteries are great, but let’s be realistic about what they can provide,” Cohn said.

Additionally, the hybrid engine system could help in future emissions that will be regulated by state and federal governments. For example, California has plans for new regulations on truck emissions that will be very difficult to meet with diesel engine vehicles, researchers said.

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