Progress in Clean Diesel Technology

Learn about the future of clean diesel technology, and take advantage of the benefits. 

“If you told me in the mid-1990s that we could put the words ‘clean’ and ‘diesel’ together, I would say you are completely out of your mind. Yet, here we are today to celebrate 10 years of clean diesel effort.”

In those two sentences, Margo Oge, director of the EPA Office of Transportation and Air Quality, summed up a decade of remarkable accomplishments in clean diesel technology and clean air regulations. Oge made her remarks during an October 2010 press conference in Washington, D.C., which highlighted the collaboration among the government, environmental organizations and the diesel industry in developing clean diesel technology.

This past February, a similar event was held in Sacramento, Calif., outside the Cal/EPA building. Leaders from the California Air Resources Board (ARB) and the diesel industry showcased the major advances in clean diesel technology—which were spurred largely due to stringent emissions standards and regulations established by the State of California and its ARB.

In a video presentation at the Sacramento press conference, ARB Chair Mary Nichols outlined the progress and future challenges in diesel technology advancements. “We’ve had tremendous success thanks to the willingness and ability of the industry to get creative when faced with the challenge of reducing emissions and nitrogen oxide and fine particulates,” Nichols said.

She then noted one of the key accomplishments of the new technology: “Today’s diesel engines emit about 90 percent less of these pollutants than they did when we first started this effort.” Over the last 10 years, emissions from heavy-duty diesel trucks and buses have been reduced by 99 percent for nitrogen oxides (NOx)—an ozone precursor—and 98 percent for particulate emissions. 

Today, it would take 60 clean diesel trucks to equal the same emissions from one pre-1988 truck. This remarkable 60 to 1 ratio is a clear indicator of the major clean diesel technology advancements. In addition, the new ultra-low sulfur diesel (ULSD) fuel that has been required since 2010 has reduced sulfur emissions by 97 percent—from 500 particulate matter (PM) to 15 PM.

Tier 4 Standards for Off-Road Equipment

More progress will be made for off-road engines and equipment. Implementation of the Tier 4 standards will come in two phases. The first phase began in January 2011 and will virtually eliminate PM emissions, while the second phase beginning in 2014 will bring the NOx emissions to near zero levels. In each case, the standards will be phased in based on engine size.

While each manufacturer will pursue their own technology path and emissions compliance strategy, several new technologies will be implemented on many Tier 4 engines and equipment. The changes that will be most noticeable for equipment will be the packaging and placement of the after-treatment system and the increased size of the air intake system to accommodate the needs for increased airflow and cooling. 

New changes to the engine will mean that engine compartments may be reworked to manage the new systems. Some OEMs have indicated they will package any new exhaust system configuration inside reworked sheet metal skin, while others will place the systems in their traditional locations with additional shielding and mounting hardware to accommodate the heavier exhaust system components. 

Most Tier 4 engines will be electronically controlled, meaning a computer will monitor and adjust the fuel and air mixture to optimize the engine’s emissions and performance on a real-time basis. In addition, changes in the engine will include new and different systems to accommodate the new engine’s increased heat rejection. For the first time, most off-road equipment will possibly incorporate emissions control technology in the exhaust system, such as a catalytic converter and/or particulate filter, typically in place of the existing muffler and exhaust system. 

New Technology Benefits for Older Diesel Engines

Through the use of new equipment, older diesel engines can improve their performance and reduce key emissions by up to 90 percent. With an estimated 11 million older diesel engines still in operation, it will be crucial for the federal, state and local governments to continue programs like the Diesel Emissions Reduction Act to modernize and help upgrade some of the older tractors, construction equipment, buses, trucks and marine vessels.

Diesel engines are the main source of power for the majority of construction equipment, and the transformation to clean diesel technology assures that continued role. But making diesel clean has not been without cost to manufacturers and users of these new machines.

Manufacturers have made extraordinary breakthroughs in technology to achieve EPA’s and California’s low emissions mandate while still preserving or improving the efficiency and performance of these work machines and equipment. Economic recovery—growth in housing, road and commercial construction and better access to affordable capital—will enable contractors to afford investments in these new low-emissions, high-performance clean diesel technologies.   

Having clean, low-emissions construction equipment will be increasingly important in the future as public and private contracts and jobs establish new emissions performance and green construction practices through state or local ordinances and give preferential treatment to companies demonstrating the use of cleaner technology.

Modernizing and upgrading existing equipment is a requirement in California and a few select metropolitan areas, but it is also a competitive strategy, particularly on bidding large public works and road construction projects. 

Another good option for contractors is engine repower and upgrade options. Particularly on larger machines and equipment, replacing an old engine with a newer one provides not only lower emissions but also reduced maintenance costs, improved productivity, fuel savings and a lower overall cost compared to new technology. 

America’s Energy Future

While the Administration is promoting an “all-of-the-above” energy strategy, more priority has typically been given to favored energy sources over other proven and available energy sources like diesel. Diversifying America’s energy sources is important, but leveraging existing technologies that already reduce our dependence on foreign oil and using advanced renewable biofuels (like clean diesel) are equally important.

Diesel engines were the power behind building America’s iconic infrastructure like the Hoover Dam and the Golden Gate Bridge. Now, diesel engines will build the next generation of roads, bridges, broadband access and more advanced energy grids. Developing natural gas resources, constructing wind farms and transporting solar panels will all require today’s powerful clean diesel engines. And today’s diesel trucks are as clean as natural gas engines. 

Over a decade, ago the diesel industry was challenged to fundamentally transform its technology to meet near zero emissions levels. Many thought it could not be done, but today’s diesel technology proves what can happen when America’s diesel engineers and equipment makers roll up their sleeves and get to work. 

Meeting these emissions challenges has delivered tangible benefits to air quality and public health and will continue to pay dividends. These accomplishments have positioned diesel as a key technology for a sustainable future in the United States and around the world.