STATEMENT OF THE MANUFACTURERS OF EMISSION CONTROLS ASSOCIATION ON THE U.S. ENVIRONMENTAL PROTECTION AGENCY S ADVANCED NOTICE OF PROPOSED RULEMAKING ON CONTROL OF DIESEL FUEL QUALITY The Manufacturers of Emission Controls Association (MECA) is pleased to respond to EPA s request for comments on the benefits of lowering the allowable level of sulfur in diesel fuel. MECA strongly supports reducing sulfur in diesel fuel used by both on-road and off-road vehicles. Reducing sulfur in diesel fuel is the critical step in achieving the goal of significantly reducing harmful pollutants currently emitted from diesel engines. MECA is a non-profit association made up of the world s leading manufacturers of motor vehicle emission controls. MECA s member companies have nearly three decades of experience and a proven track record in developing and commercializing exhaust control technologies for diesel-powered vehicles and equipment. These companies have gained considerable knowledge on the impacts of sulfur in fuel on exhaust control technologies. SUMMARY To date, emissions reductions from diesel engines largely have been achieved through engine design changes and modest improvements in diesel fuel quality. These reductions are inadequate to enable many states to meet the applicable National Ambient Air Quality Standards and to address the growing concern with toxic emissions from diesel engines. Important additional emission reductions are possible today by employing exhaust control technology that can be operated on engines using current diesel fuel. In order to reduce harmful emissions from the diesel engine to the very low levels needed, however, a systems approach utilizing advanced engine designs, advanced and integrated exhaust control technologies, and low sulfur fuel must be utilized. The current U.S. diesel sulfur levels for on-road vehicles is as high as 500 ppm and for nonroad vehicles and equipment as high as 5000 ppm. Fuel sulfur at these levels is a major barrier to several NOx control technologies, such as NOx adsorbers and lean NOx catalysts (DeNOx). Demonstrations of these NOx exhaust control technologies have shown the potential to control from greater than 50 percent to over 80 percent of engine-out NOx emissions. These NOx control technologies would provide engine manufacturers with the added flexibility to design engines for improved fuel economy while allowing the exhaust controls to reduce NOx levels. Unfortunately, the current levels of sulfur in commercially available diesel fuel will preclude the use of these technologies since the catalytic reaction required to reduce the NOx emissions is adversely impacted by exposure to sulfur which attaches to the chemical sites and impairs its performance and longevity. 1
The current sulfur levels are also a barrier to certain attractive and commercially available low sulfur catalytic diesel particulate filter utilizing an upstream NOx conversion catalyst to facilitate filter regeneration while achieving PM reductions in excess of 90 percent. Other PM control technologies, such as diesel oxidation catalysts and catalyzed diesel particulate filters, which are now designed to operate on current fuels, would achieve significantly improved performance with lower sulfur fuel. The application of selective catalytic reduction (SCR) for NOx control to applications characterized by low exhaust gas temperatures will require the use of catalysts that are adversely affected by sulfur. Substantial research and development efforts clearly demonstrate that sulfur levels below 30 ppm will be necessary for a truly clean diesel engine. Evidence is growing that levels <5 ppm may be necessary to enable the use of the NOx adsorber. MECA has prepared a report entitled The Impact of Sulfur in Diesel Fuel on Catalyst Emission Control Technology which evaluated the existing technical data on the issue of diesel sulfur impacts on catalytic exhaust control technologies. A copy of the report was previously provided to EPA and a copy is attached to our statement. Also attached to our statement is a report prepared by MECA entitled Demonstration of Advanced Emission Control Technologies Enabling Diesel-Powered Heavy- Duty Engines to Achieve Low Emission Levels. This report summarizes the test results of a program conducted by MECA evaluating several PM and NOx control technologies on a 1998 model year heavy-duty engine operated on fuels with sulfur levels at 368 ppm, 54 ppm, and zero ppm. This program demonstrated that over the full range of technologies, emission control performance could be improved significantly by reducing the sulfur level in the fuel. MECA is also participating with the U.S. Department of Energy (DOE) and the Engine Manufacturers Association (EMA) in a comprehensive test program designed to further assess the impact of sulfur at various levels on a number of different NOx and PM exhaust control technologies. We anticipate that the results of this test program will be available by the fall of this year. A number of organizations have endorsed an approach calling for a 30 ppm sulfur cap in 2004 and a near zero sulfur diesel fuel in the 2007 time frame. MECA believes there would be substantial benefits to such an approach, and we support such a program, provided adequate lead time exists for refiners to make the necessary improvements to the refinery process to ensure the availability of such fuel. Also, we believe every effort should be made to promote the early introduction of low sulfur diesel fuel. In that regard, we note that ARCO is initiating a pilot demonstration program in which it will provide diesel fuel with sulfur levels <5 ppm. Several different types of vehicles and control technologies will be evaluated on the low sulfur fuel. Several MECA member companies are providing technology and technical support for this pilot program. MECA also supports reducing, as soon as possible, the sulfur levels in diesel fuel for nonroad vehicles and equipment to levels currently required for on-road diesel fuel. Eventually, off-road diesel fuel should meet the same low levels established for on-road diesel fuel to allow utilization of the full range of exhaust control technologies which are expected to be used on onroad vehicles once low sulfur fuel is available. 2
RESPONSE TO SPECIFIC QUESTIONS POSED BY EPA Below are MECA s responses to those questions raised by EPA which are within our area of expertise. ISSUE 1: Fuel Changes other than Sulfur While air quality gains could be realized by improving other parameters of diesel fuel, without question the most beneficial fuel improvement is reducing the sulfur in diesel fuel. As noted above, low sulfur fuel would enable the use of the full range of catalyst-based exhaust control technologies; technologies capable of reducing PM emissions in excess of 90 percent, NOx emissions by 80 percent or more, and toxic hydrocarbons (HC) by 80 percent or more. In addition, low sulfur fuel would lower engine-out emissions and enhance engine life by reducing the corrosive gases involved in engine wear. If a diesel fuel quality program structured to encourage gas-to-liquid or other nonpetroleum blends would increase the supply of cost-effective low or zero sulfur fuel for use by diesel engines, then MECA certainly supports such an initiative. ISSUE 2: Experience Outside the United States The experience in Europe, where low sulfur fuel was mandated in 1998 to take effect in 2005, provides several useful lessons. First, once the standards were established, competition in the marketplace and tax credits promoted significant initiatives to pursue cost-effective compliance and early introduction of low sulfur diesel fuel. Indeed, once the requirements were established, a number of refiners announced plans for the introduction of low sulfur fuel well ahead of the mandated deadline. There has been an increase in the sale of what is being referred to in Europe as ultra low sulfur fuel (ULSD) (<10 ppm and <50 ppm sulfur) and the number of refineries producing this product. For example, Hart s Diesel Fuel News reported that all sales of diesel fuel in Great Britain would be ULSD (<50 ppm) by the end of 1999; current sales of ULSD is reported at 60-70 percent of the market in Great Britain. We anticipate that if EPA establishes low sulfur diesel fuel requirements, some refiners in the U.S. may also commit to the early introduction of low sulfur fuels. Incentives played a major role in the European refiners decision to introduce low sulfur diesel fuel early. The use of tax credits has proven extremely effective in creating the necessary incentives. While the use of tax credits historically has been met with political opposition, EPA should explore the concept and the full range of potential incentives that could be provided to encourage refiners to introduce low sulfur fuel before the mandatory deadlines. Second, in areas in Europe, such as Sweden, Finland, Denmark, Germany and Great Britain, where diesel fuel with very low sulfur is already available, diesel particulate filters are being commercially introduced on heavy-duty diesel trucks and buses. To date over 5000 vehicles 3
have be equipped with controls. Vehicles equipped with these filters are achieving PM reductions of up to 90 percent or more. Also, Volvo recently announced that it will offer a diesel particulate filter, which requires the use of low sulfur fuel, as a factory option for trucks and buses. Finally, Peugeot-Citroen (PSA), in announcing that it will introduce passenger cars in 2000 equipped with an integrated diesel particulate filter employing a fuel-borne catalyst, noted that its integrated emission control system would have better performance in NOx abatement when low sulfur fuel (30 ppm) is widely available. ISSUE 3: Sulfur-Tolerant Technologies As noted above, for the diesel engine to achieve low emission levels, catalyst-based control technologies will be needed and these technologies are adversely affected by the current level of sulfur in diesel fuel. For example, SO in the in the exhaust is converted to SO over a 2 3 precious metal catalyst. The SO rapidly hydrolyzes to H SO (a sulfate) as the exhaust leaves the 3 2 4 tail pipe. Without low sulfur fuel, we believe light-duty, diesel-powered vehicles will not be able to meet the proposed Tier 2 NOx and PM standards. Similarly, for heavy-duty diesel engines, low sulfur fuel is critical to enable very low emission levels to be achieved. While work continues to reduce the impact of sulfur on catalyst-based control technologies, a completely sulfur tolerant catalyst does not exist, nor do we anticipate that one will be developed. For a more detailed analysis on this issue, we refer EPA to the two above-referenced MECA technical papers. Also, we anticipate that the joint DOE/EMA/MECA test program (DECSE) referenced above, when completed, will provide extremely useful data on this issue. ISSUE 4: Sulfur-Sensitive Technologies With the appropriate limit on sulfur in fuel, we believe the full range of commercially available and emerging catalyst-based control technologies can be designed as part of the system to meet the applicable useful life requirements for both light-duty and heavy-duty applications. An issue that needs further evaluation is the impact of sulfur in lubricating oil on certain catalystbased technologies, such as the NOx adsorber. The extent of any impact will be related to the levels of sulfur in the lubricating oil and the amount of lubricating oil consumed. MECA would be happy to work with EPA in evaluating this issue. ISSUE 5: In-Use Emissions As noted above, exhaust control technology can, and, is being, designed as part of a complete and integrated system to provide effective emission control over the full range of vehicle operating conditions and to meet the applicable durability requirements. These efforts would be greatly enhanced by the availability of low sulfur fuel. For example, current sulfur levels limit the ability of an oxidation catalyst to light-off at very low temperatures and cause sulfate formation at high temperatures, thereby reducing the overall effectiveness of catalyst-based controls to reduce PM emissions. The choice of catalyst formulations is limited by the potential to make sulfate. 4
While effective catalysts have been designed for both diesel oxidation catalysts and diesel particulate filters with current fuel sulfur levels, the overall performance is significantly improved when low sulfur fuel is used. For certain catalyst-based diesel particulate filters, the presence of sulfur at current levels is a complete barrier to some commercially available technologies and limits the effective operating range and breadth of vehicle applications for other filter technologies. For lean NOx catalyst technology, lower sulfur fuel would enable the operating window for effective control to be expanded through the use of catalyst formulations that currently cannot be used because of the current levels of sulfur in diesel fuel. Issue 6: Selective Catalytic Reduction Issues related to ammonia slip, infrastructure, reductant maintenance, robustness and possible N2O can be, and, are being, resolved for SCR technology. The robustness and operating effectiveness of SCR on motor vehicle applications is currently being demonstrated in a multivehicle pilot program in which several vehicles equipped with SCR systems have maintained effective operating performance for extended mileage, in some cases over 200,000 or more kilometers (See SAE Paper No. 1999-01-0111). An effective strategy for controlling ammonia formation ( slip ) is to utilize an oxidation catalyst or a catalytic filter, which also provides PM and toxic HC emission control. But again, sulfur in the fuel inhibits the effectiveness of these oxidation catalyst and catalyst-based filter technologies. Also, lower sulfur fuel would enable SCR catalyst manufacturers to utilize the full range of catalyst formulations in order to expand the effective operating range of the SCR catalyst system (i.e., the use of precious metal catalysts, which are effective at reducing NOx emissions at lower temperatures, is limited by current sulfur levels). Compact SCR systems, which use an oxidation catalyst upstream of the SCR catalyst, seem to effectively address the N O formation issue. 2 ISSUE 8: Durability and Maintenance Impacts For diesel oxidation catalysts and diesel particulate filters designed to operate on 500 ppm sulfur fuel, performance, durability, and maintenance is not adversely affected. For some SCR systems, ammonia sulfate deposits accumulate downstream of the SCR catalyst requiring periodic washing. Lower sulfur will greatly enhance the durability of all catalyst-based control technologies. This fact is illustrated by the experience in Sweden with PM control technologies successfully operating for extended periods where low sulfur fuel is used. We anticipate that the DECSE program mentioned above will provide useful data confirming this conclusion. ISSUE 9: Diesel in Tier 2 MECA member companies are investing substantial R&D funds to develop, optimize and commercialize the catalyst-based PM and NOx exhaust control technologies that will be a necessary part of an integrated engine/control/fuel system designed to meet the Tier 2 standards. If low sulfur fuel is available, we believe these standards can and will be met. But without low sulfur diesel, the full range of control strategies will not be available and the prospects for compliance with the Tier 2 standards become very uncertain. 5
As stated above, while MECA s members continue efforts to reduce the impact of sulfur on catalyst-based technology, a sulfur-tolerant catalyst that would enable light-duty vehicles to meet the Tier 2 standards does not appear feasible. The early availability of low sulfur fuel would be extremely helpful in the introduction and demonstration of systems capable of making the diesel engine extremely clean. We would encourage the early introduction of low sulfur fuel as soon as possible. In that regard, we again note that one California refiner recently announced plans to make available a very low sulfur fuel, and a pilot test program to demonstrate the air quality benefits of this fuel is getting underway. ISSUE 10: Future Heavy-Duty Engine Standards While differences exist in controlling emissions from light- and heavy-duty diesel engines, the basic catalyst-based engineering and development considerations are similar. Obviously, one important difference is the extended durability requirements for heavy-duty engines. Consequently, the negative impacts of sulfur on certain sulfur sensitive integrated emission control systems, which is an issue for light-duty vehicles, will be more serious for heavy-duty applications. The current and 2004 on-road HDE standards require such modest levels of emission control that in all but a few cases, exhaust controls will not be required. Thus, sulfur is a nonissue as it relates to catalyst-based controls. Nevertheless, engine manufacturers have indicated that the current sulfur levels do adversely affect the likely non-catalyst control strategies that will be used to meet the 2004 standards. With low sulfur fuel and utilization of advanced engine designs and catalyst-based PM and NOx control strategies, we believe, with adequate lead-time, levels of <1.0 g/bhp-hr NOx and <0.01 g/bhp-hr PM standards can be achieved for HDEs. ISSUE 11: Retrofit Potential Currently, diesel oxidation catalysts and diesel particulate filters that are designed to operate on fuel with current sulfur levels are being successfully retrofitted on urban buses and commercial, industrial, and mining equipment and vehicles in the U.S. and around the world. These systems have demonstrated excellent durability. Sulfur sensitive technologies can be readily retrofitted on both on-road and nonroad engines. In Europe, where low sulfur fuel is available, diesel particulate filters have been, and are being, installed in Sweden, Great Britain, Germany, Finland, Denmark, and France. As noted above, many of the systems in Sweden have been operating for several years, and after extended mileage accumulation, are maintaining effective control. ISSUE 12: Future Nonroad Diesel Engine Standards Current nonroad emission standards are so lenient that they do not require the use of any 6
exhaust control technology. Even if the Tier 3 standards were set at the level of the 2004 on-road standards, we do not believe exhaust control technologies will be needed. If, however, sulfur were reduced to the current on-road diesel sulfur limits, oxidation catalyst could be employed which could reduce PM emissions by up to 30 percent and toxic HC emissions by up to 60 percent or more. If lower sulfur fuel were available, the types of integrated control strategies that are expected to be used on future on-road engines, could be applied to nonroad engines, and NOx, PM and toxic HC emissions could be cut to a fraction of the levels that will be emitted under EPA s current regulations governing nonroad engines. ISSUE 13: A Cap on Nonroad Fuel Sulfur Levels Regardless of whether sulfur levels in nonroad diesel fuel would increase as a result of lowering sulfur levels in on-road diesel fuel, a sulfur limit for nonroad diesel fuel should initially be established at the level currently required of on-road diesel fuel and eventually at the low levels we anticipate will be established for on-road diesel fuel in the future. ISSUE 14: Sulfur Reduction Methods Our only comment on this issue is that EPA should establish a requirement that prohibits refiners from blending up the level of sulfur in diesel fuel. When EPA established the regulations for leaded gasoline, the Agency expressly prohibited blending up the levels of lead in leaded gasoline. EPA did not establish a similar prohibition when it adopted in the early 1990s the limit on sulfur in diesel fuel. As a consequence, some refiners reached very low levels of sulfur in the processing and blended up the levels of sulfur in the fuel. ISSUE 22: Uncertainties The diesel engine has many significant benefits which will preserve a strong demand for its usage. If low sulfur fuel becomes available, we believe the diesel engine can become an extremely clean power train. To minimize any uncertainties, EPA should clearly define the sulfur reduction schedule as soon as possible, as well as the expected future emission limits for the diesel engine beyond the current 2004 on-road standards and the current standards applicable to nonroad engines. With adequate lead time and clearly defined requirements, the refining industry, the engine and vehicle manufacturers, and the emission control industry can commit the necessary resources to develop the respective products and technologies to meet those requirements in a timely and cost-effective manner. ISSUES 24 and 25: Phased Approach and Coverage While the preferred approach would be to introduce low sulfur fuel nationally at the same time to avoid a duel fuel infrastructure and the possibility of misfueling, we believe a phased approach can be designed to be effective. Significant air quality benefits would be realized from the early introduction of low sulfur fuel for targeted markets. Of course, care must be taken to assure the availability of low sulfur fuel for the intended markets, and steps must be taken to 7
insure that inadvertent or intentional misfueling does not occur. ISSUE 27: Ability to Accommodate Some Higher Sulfur Fuel If the exposure to high sulfur fuel is limited, the potential exists for catalyst performance recovery to be achieved through some method of regeneration (e.g., a sufficiently high exhaust temperature to purge the sulfur from the catalyst surface). Long term exposure to high sulfur levels will negatively affect all systems during high sulfur use. Regeneration methods may differ in their effectiveness depending on the system involved. CONCLUSION MECA strongly supports an EPA initiative to establish sulfur limits for both on-road and nonroad diesel fuel. If low sulfur diesel fuel is made available, we believe an important opportunity exists to substantially reduce PM, NOx, and toxic HC from the both on-road and nonroad diesel engines. We would be pleased to assist EPA in its consideration of this important issue. 8