May 29, 2019 10:00 AM, EDT

Perspective: Diesel Drives Toward Clean Energy Future

There was a time not long ago when methanol was being hailed as the replacement for diesel fuel. The year was 1987, and environmental concerns were coming into vogue. In California, state regulators’ efforts to reduce vehicle emissions were — as they are today — making headlines.

Allen Schaeffer


Seeking to take definitive action to address the smog that hung over the state, California air regulators decreed that methanol would replace diesel fuel, making the case that it was a cleaner-burning liquid fuel that produced no particulates. However, problems arose. Among these: Methanol burned without a flame, posing risks in handling, storage and accident settings, and when it spilled or leaked, it created severe groundwater contamination.

Methanol failed as a stand-alone agent of change for the future — today, methanol-powered trucks are nowhere to be found. However, talk of what will supplant diesel as the power source of tomorrow is as rampant as ever. But the conversation isn’t about one solution; the developments that could reshape the future of trucking run the gamut from reducing vehicle-miles-traveled and moving to drone-only package delivery, to a federal mandate that commercial fleets use nothing but all-electric commercial vehicles. While most of these ideas aren’t at commercial scale today, they are options being explored — or will be — and their success will be best measured over the next few years, if not decades.

The journey to cleaner diesel fuels, particulate filters and near-zero nitrogen oxide engines that took place in the 1990s through today has not been entirely smooth. But, we have witnessed the diesel engine develop into a near-zero emissions technology. It was a challenge for both manufacturers and their customers to be patient as engineers worked to meet dual challenges of near-zero emissions and boosting fuel economy.

But a more than decade later, here we are. Diesel is time-tested, battle proven, reliable and constantly improving — enough to dominate the trucking industry for more than half a century. It remains the gold standard for trucking today. It would take more than 60 of today’s modern diesels to equal the emissions of a single model from the 1990s. That’s progress. And yet more is being asked of truck and engine manufacturers in the clean and efficient diesel department.

Manufacturers and their suppliers are trying to thread the needle to the future, and a peek at that work is encouraging. They are using advanced materials, coatings and designs for tomorrow’s key engine components, such as pistons, rings and seals. Component suppliers are enhancing turbo-charging techniques, fuel injection and engine management strategies. Emissions-control suppliers are producing advanced substrates, filters and wash coatings to scrub emissions more efficiently under varying conditions. All of this is being done in the race to make diesel even cleaner and more efficient.

At the same time, original equipment manufacturers are launching new electrified truck options and are exploring interesting options such as pairing diesels with hybrid-electric technology.

Another significant opportunity for fleets lies in using advanced biodiesel fuels in diesel engines. This combination reduces greenhouse gas emissions by at least 50%, and up to 80% if renewable diesel fuel is used — without requiring any engine or vehicle conversions or the build-out of new fueling infrastructure. A growing number of cities are doing this at scale today.

How trucks are operated also makes a big difference, as the “Run on Less” campaign from the North American Council for Freight Efficiency showed. After more than 50,000 miles, the seven Class 8 diesel trucks in the 2017 demonstration averaged about 10 mpg, even with heavy loads of more than 65,000 pounds. Some trucks exceeded 12 mpg.

Ultimately, clean air and environmental progress come from truckers and fleet managers who are buying and using newer technologies and delivering the benefits. Today, the 4.9 million new-technology diesel trucks on America’s roads have removed more than 26 million metric tons of NOx and 59 million metric tons of carbon dioxide from the air. Currently, across the United States, more than 36% of all Classes 3-8 registered commercial trucks are of the newest, near-zero generation diesels, and that number grows each year.

We’re straddling two worlds today — one of energy abundance and one of the clean energy future. Diesel has its place in both worlds, answering the dual calls of clean and efficient operation. How lucky we are to have many improving options and choices.

Will the future be all electric? Only time will tell. I do know that wherever the future takes us, diesel power will help get us there.

Allen Schaeffer is the executive director of the Diesel Technology Forum, a nonprofit organization dedicated to raising awareness about the importance of diesel engines, fuel and technology. Schaeffer was formerly an environmental specialist for American Trucking Associations and served as ATA’s vice president of environmental affairs from 1995-2000.