Fueling the Future: Clean diesel

When the U.S. Environmental Protection Agency announced five years ago diesel fuel sulfur levels would drop to 15 parts per million for on-highway vehicles in 2006 and off-highway in 2010, the engine manufacturers knew they had a lot of work to do. No one would argue that reducing emissions wasn’t a win for the environment, but the effects on trucks and off-road equipment became a major question mark. Engine manufacturers and oil companies worked together to create new exhaust aftertreatment systems and lube oils – two things that when combined with ultra low sulfur diesel cut emissions by more than 75 percent – to comply with 2007 on-highway engine regulations.

The end result: At the Cummins test facility in Columbus, Indiana, last October, EPA Administrator Stephen Johnson called ULSD “the single greatest achievement in clean fuel since lead was removed from gasoline more than 25 years ago.”

The overwhelming benefits of ULSD (see sidebar on page 32) led manufacturers to accept it as the fuel of the future. “Widespread use and adoption of ULSD is good for the industry and the environment,” says Darrin Drollinger, vice president of statistics, safety and technical services, Association of Equipment Manufacturers. “Off-road equipment manufacturers fully support a cleaner environment and are eager to produce the safest and cleanest possible engine emission technologies that the customer will buy.”

Al Mannato, fuel issues manager, American Petroleum Institute, also hopes clean diesel will improve diesel’s image. “Diesel fuel is perceived as ‘dirty’ by the motoring public,” he says. “This process enables diesel to be as clean as gasoline. There won’t be big puffs of black smoke coming out of vehicles.”

Around the bend
Encouraged by the smooth ULSD rollout the on-highway market experienced, few problems are anticipated for the 2010 off-highway transition. Educating consumers and shaping public perception could be the next test for ULSD, Drollinger says. “A big challenge is the one of industry communication – that ULSD is fine to use and provides significant environmental benefits,” he says.

Dollars and sense
A key concern ULSD must overcome is cost. According to the Energy Information Association, a statistical agency of the U.S. Department of Energy, diesel prices have largely been higher than gasoline prices since September 2004. Worldwide demand for diesel fuel has steadily increased each year, and the EIA expects the U.S. average for diesel at the retail level to remain approximately $2.70 per gallon through 2008. A key factor in this calculation relies on the EIA’s forecast for the price of West Texas Intermediate crude oil to average about $64 per barrel. Since ULSD costs 4 to 5 cents more per gallon to produce than LSD, expect some cost to be passed on to the end user. “The current ULSD price is 8 cents more per gallon than for low sulfur diesel,” says Ken Simonson, chief economist, Associated General Contractors.

Whatever the cost, customers will be hard-pressed to find any diesel fuel other than ULSD. According to the API, current ULSD production has reached 90 percent of on-highway fuel production and 70 percent of the entire diesel distillate pool. Although oil companies offer both LSD and ULSD at present, the numbers of suppliers for LSD will drop over time. “It’s not cost effective for a manufacturer to maintain an inventory of regular diesel and produce ULSD,” says Brian Schmidt, manager, off-highway division, Chevron. Mannato agrees. “Some smaller refineries will produce a higher sulfur product, but as the years pass there will be less and less,” he says. (See chart on page 34.)

Since ULSD is backward-compatible with pre-2007 engines, a lack of LSD won’t pose a problem. Although you don’t gain big emissions benefits when using ULSD in older engines, the sulfur reduction is still good for your engine, as long as you are willing to pay the cost premium for ULSD. With 2007 and later engines, you don’t have a choice. According to Don Stanton, director of advanced engine development research and technology at Cummins, advanced aftertreatment systems are highly sensitive to sulfur levels. Using LSD in the new engines will clog the exhaust aftertreatment devices, compromising their effectiveness and increasing maintenance costs.

Devil in the details
Using ULSD doesn’t extensively reduce emissions single-handedly. According to the EPA, using ULSD on its own results in a 5 to 9 percent reduction in emissions, depending on the baseline sulfur level. The real benefit of ULSD occurs when it’s paired with advanced diesel engine technology designed to further reduce harmful nitrogen oxide (NOx), particulate matter, carbon monoxide and hydrocarbon emissions. Engine manufacturers realized from the outset new regulations would mean looking closely at engine hardware and lubricants. Years of research and design followed, with teams of OEM engineers developing advanced new engines designed to lower emissions without sacrificing performance. What’s the result of their work? Advanced emissions control devices lower particulate matter emissions to nearly zero, says the Clean Diesel Fuel Alliance, a public-private partnership formed to ease the transition to ULSD.

Lowering emissions meant equipping new diesel engines with aftertreatment systems such as diesel particulate filters and diesel oxidation catalysts, designed to reduce exhaust emissions, thereby reducing particulate matter. The DPF burns exhaust gases and captured carbon particles, while the DOC uses a heated catalyst to burn contaminants, converting them to carbon dioxide and water vapor.

Engine technology such as exhaust gas recirculation (EGR) lowers emissions by pumping recirculated exhaust gas into the combustion chamber. However, EGR technology does precipitate soot loading, and 2007 engines run hotter than previous engines, causing oils to deteriorate faster. Oil companies responded with increasingly robust lube oil formulas and this year introduced the CJ-4 spec, which lowers the amount of ash in the engine’s DPF, extending cleaning intervals for the filter. DPFs should be able to go 150,000 miles between cleanings, according to the EPA. “Engine manufacturers design the engines to reduce the likelihood of increased soot loading,” Stanton says. “Likewise, we work with OEMs to integrate new engine technology with the vehicle’s cooling system to mitigate oil deterioration.”

Stanton says users should notice little if any difference when using ULSD compared to diesel and low sulfur diesel. “Most engine manufacturers do not see a major impact on service intervals, and do not expect the time between service intervals to change significantly,” he says.

Side effects of refining at a higher level
Sulfur creates an acidic environment inside an engine in addition to negatively impacting exhaust gas emissions, so removing it from diesel fuel is a plus. When using advanced sulfur removing technology, it does more than lower sulfur. It also removes high-energy “aromatics” and will make the fuel slightly less dense, Schmidt says. The ULSD has a lower energy density than diesel containing higher sulfur content, which translates to reduced fuel economy. The potential reduction in fuel economy has been estimated at one percent. However, any small decrease in fuel economy can easily be handled with sensible conservation efforts. Less time idling, best use of gearing, and applying best practices tied to maintenance can more than make up for a 1 percent drop in economy, according to Schmidt.

The advanced desulfurization process also removes some of the naturally-occurring lubricity compounds in the fuel – compounds needed to lubricate fuel systems in diesel engines. “Lubricity additives introduced in the refinery will take care of the problem,” Schmidt says. “ULSD is a clean burning fuel that works well in construction equipment.”

Schmidt did note that blending ULSD with biodiesel, which also helps with lubricity, will improve problems associated with cold weather conditions. At low temperatures, diesel fuel forms wax crystals, which can clog fuel lines and filters in a vehicle’s fuel system. The “cloud point” is the temperature at which the fuel starts to appear cloudy, indicating that the wax crystals have begun to form. At even lower temperatures, diesel fuel becomes a gel that cannot be pumped. The “pour point” is the temperature below which the fuel will not flow. The cloud and pour points for biodiesel are higher than those for petroleum diesel. Therefore, ULSD will improve the cold temperature properties of biodiesel and help decrease the issues around filter plugging and cold starts.

In Minnesota, a state that has been using a B2 biodiesel-ULSD blend, isolated instances of fuel filter clogging occurred over the winter which was not associated with the formation of wax crystals and ambient temperatures dropping below the cloud and pour point of the blend. Since sulfur inhibits microbial growth, any fuel with a lower sulfur content than diesel can promote bacterial growth. Tim Worke, transportation and highway director, Minnesota Associated General Contractors, says the state’s AGC is participating in a diesel fuel users roundtable, along with representatives from Minnesota’s trucking association, aggregates and ready mix industries, the mining industry and petroleum marketers, to address issues.

In the pipeline
One of the biggest challenges of the ULSD transition has been avoiding contamination from diesel with sulfur levels greater than 15 ppm. According to the Association of Oil Pipelines, a trade organization that represents common carrier crude and product petroleum pipelines, there are more than 200,000 miles of oil pipelines in the United States. Since the pipelines transport both crude oil and refined products, the potential for ULSD contamination from a distillate higher in sulfur could not be ignored. Although the pipelines use metal plugs to separate batches, refiners took additional steps to ensure proper sulfur levels. API’s Mannato says refineries are holding to the 15 ppm specification by producing ULSD in the 7-to-8 ppm range. By producing the fuel at a sulfur level well below EPA requirements, refiners reduce the chance of contamination. “We haven’t had significant problems with contamination,” Mannato says. “We’ve introduced a clean product into the distribution system and kept the integrity of the product.”

Although contamination hasn’t been an issue, labeling has. Following the initial rollout, Mannato says 40 percent of retail stations had no labels indicating the fuel was ULSD. Although sampling proved that 80 percent was ultra-low sulfur diesel, customers had no way of knowing if the fuel in the tank was ultra-low or low sulfur diesel. “The EPA moved out and issued citations, and the problem is adjusting itself,” he says. Retail stations have a strong incentive to comply with labeling requirements. EPA fines for mislabeling pumps can reach $32,000 per day for each violation.

No loose ends in 2010
So far, the on-road ULSD rollout has happened with barely a hitch – a testament to the manpower hours, billions of dollars and bold strategies manufacturers devoted to the transition. Not only has the shift to ULSD happened smoothly, the EPA Clean Diesel Campaign requirements facilitated the development of advanced new technologies and superior lubricants. Will the transition to ULSD in off-road equipment in 2010 happen as smoothly? Those who have worked on the technology are confident the off-road transition will be similar to the on-road rollout. “We design both our off- and on-road engines to the same high standards,” Cummins’ Stanton says. “The duty cycles are different, and often more demanding for off-road applications, but we design well beyond the worst case scenario.”

Equipment manufacturers and oil companies are telling contractors to go ahead and use ULSD, with a nod to some minor changes. According to John Deere, the introduction of ULSD fuel to older vehicles may adversely affect fuel system components, mainly seals, and loosen deposits in fuel tanks. Deere recommends owners and operators of existing diesel equipment monitor their machines closely for potential fuel system leaks or premature fuel filter plugging during the changeover to ULSD fuel. Chevron, likewise, notes contractors must watch for leaks and clogs during the initial transition, but most won’t encounter significant problems, says Schmidt. “With respect to how ULSD performs in construction equipment, it’s not much different than regular diesel,” he says.

So now that manufacturers and refiners have spent billions of dollars and years developing the technology and systems needed to produce ULSD, what will be the ultimate benefit? Supposedly, you can’t put a price on your health, but the EPA has a dollar figure: the fully-implemented Clean Air Diesel final rule will result in more than $70 billion annually in environmental and public health benefits.

Sulfur is present in crude oil and forms sulfur dioxide gas when fuel is burned. Dissolving in water vapor to form acid, sulfur dioxide interacts with particles in the air and forms sulfates. Another pollutant, nitrogen oxide, forms during the combustion process when fuel burns at high temperatures. Both nitrates and sulfates mix with small particles such as organic chemicals, metals, dust and soil to form particulate matter. Although PM such as dust, dirt or smoke is large enough to see with the naked eye, fine particles can be 2.5 micrometers or less – 30 times smaller than a human hair. Particles less than 10 micrometers in size cause health problems because they are so fine they can enter your lungs or bloodstream.

PM exposure causes a variety of problems including airway irritation, breathing difficulty, coughing, decreased lung function, aggravated asthma, chronic bronchitis, irregular heartbeat, non-fatal heart attacks and premature death in individuals with heart or lung disease. According to the EPA, PM causes a great deal of damage because wind carries the particles over long distances before they settle on land or in water. PM makes lakes and steams acidic, depletes nutrients in the soil, damages forests and crops, changes the nutrient balance in coastal waters and river basins and causes acid rain.

Once completely implemented, the EPA says its regulations will remove 2.6 million tons of smog-causing nitrogen oxide emissions and 110,000 tons of soot or particulate matter per year. The clean diesel campaign will prevent an estimated 8,300 premature deaths, 5,500 cases of chronic bronchitis and 17,600 cases of acute bronchitis in children annually, according to the EPA. They also say approximately 360,000 asthma attacks and 386,000 cases of respiratory symptoms in asthmatic children will be prevented, as well as 1.5 million lost work days, 7,100 hospital visits and 2,400 emergency room visits.