PM 2.5 Emissions Reduction for Two-Stroke Engines

Small particulate emissions, such as those that fall within the PM2.5 classification, have a substantial negative effect on air quality and human health. Significant sources of PM2.5 emissions are small two-stroke engines that are used in outdoor power equipment such as leaf blowers, chain saws, and string trimmers, as well as larger two-stroke engines used in recreational vehicles such as all-terrain vehicles (ATVs), motorcycles, snowmobiles, and marine outboard motors. These engines account for roughly 25 percent of the PM2.5 emissions from the 2020 NONROAD emission inventory. Furthermore, because the operators of these engines typically are very close to the source of the PM2.5 emissions, the health effects will be heightened relative to other PM2.5 sources. PM2.5 emissions from small handheld tow-stroke engines have decreased in recent years as a result of EPA regulations on these engines. However, these emissions are still very high compared to conventional four-stroke engines. In addition, further substantial decreases in PM2.5 emissions are not likely because the remaining emissions are almost exclusively due to the oil added to the fuel for necessary lubrication of the two-stroke engines. The innovation proposed is to reduce PM2.5 emissions from current two-stroke engine levels by a factor of 5 or greater by modifying the two-stroke engine. The project objective is to demonstrate that Aerodyne Research’s PM2.5 reduction approach can be achieved while maintaining very good durability of the two-stroke engine and maintaining the gaseous emissions performance throughout the rated life of the engine. The project also will demonstrate the cost effectiveness of the PM2.5 emissions reduction approach. Successful Phase I and II programs will provide a strong boost for wide commercialization of this technology because both the effectiveness of the PM2.5 reduction approach and the durability of the engines that use this approach will have been demonstrated. The potential commercial applications of the PM2.5 emission reduction technology are very large. Two-stroke engines are used in a wide variety of applications, and this technology is applicable to all two-stroke engines. The benefits of this technology are broad, ranging from greatly reduced health effects for users of portable power equipment to improved air quality throughout the United States and overseas.