Emission control technologies make tighter standards possible
12 Since the time the Regulation 13 NOx emission limits were chosen, the marine industry has continued researching emission control technologies for marine diesel engines. Engine manufacturers are exploring ways to transfer land-based diesel engine technologies to marine diesel engines and are developing new marine-specific technologies. These include combustion optimization (timing retard, combustion chamber geometry, and swirl), advanced fuel injection controls, improved charge air characteristics (jacket-water aftercooling, raw water aftercooling, separate-circuit aftercooling), electronic controls, exhaust gas recirculation (EGR cooling, soot removal), exhaust aftertreatment devices (oxidation catalysts, particulate traps, selective catalytic reduction), and water emulsification. 4 Test data acquired by US EPA in connection with the domestic marine diesel engine control program suggest that the use of these technologies results in significant reductions in NOx emissions. Wartsila NSD has also been experimenting with technologies for very large ocean-going propulsion engines. They estimate that direct water injection technologies can achieve a 50 to 60 percent reduction in NOx emissions. This technology can be used with all fuel types and is available for retrofit operations. Selective Catalyst Reduction (SCR) techniques can achieve 85 to 95 percent reductions in NOx. In addition, Sweden has achieved NOx emissions reductions in excess of 90% for numerous vessels that have applied different technologies as a result of its national program implemented in January 1998.
13 US EPA estimates that a conservative application of these technologies can result in meaningful emission reductions from new marine diesel engines. For example, the US EPA Tier 2 limits are equivalent to a 20 to 25 percent reduction from the Regulation 13 levels, and phase in over 3 years, beginning in 2007. These limits are projected to achieve an additional 7 percent reduction in NOx emissions as early as 2010, increasing to 15 percent in 2020. While the United States domestic commercial marine diesel engine rule did not consider alternative standards for very large engines, it is clear that meaningful emission reductions could be achieved if new low NOx engine technologies were applied to those engines as well.
14 In summary, the above information suggests that it is appropriate for the Committee to begin considering a second tier of emission limits for marine diesel engines at or above 130 kW. A second tier of standards, set at 25 to 30 percent below the Regulation 13 limits, will ensure meaningful NOx reductions and associated reductions in ozone formation. Alternatively, a second tier of standards that flattens the current NOx curve and lowers the overall limits can be considered. These tier 2 standards can be developed to go into effect in 2007, allowing a 7-year period of stability for the current Regulation 13 limits and permitting engine manufacturers to adjust their engine designs to include these new emission control technologies. This second tier of standards could also include market incentives to encourage manufacturers to produce even cleaner engines.
4Final Regulatory Impact Analysis, infra.
