EPA Proposes More Stringent Emissions Rules for Small Nonroad and Marine Spark-Ignition Engines

18 April 2007

The US Environmental Protection Agency is proposing new, more stringent exhaust emissions rules for the small spark-ignition engines in lawn and garden equipment and small recreational watercraft.

The engines and vehicles covered by this proposal are significant sources of air pollution. They account for about 25% of mobile source hydrocarbon (HC) emissions and 30% of mobile source carbon monoxide (CO) emissions.

Americans spend more than three billion hours per year using lawn and garden equipment. Currently, a push mower emits as much hourly pollution as 11 cars and a riding mower emits as much as 34 cars.

To meet the new exhaust emission standards, manufacturers are expected to use catalytic converters for the first time ever in many types of small watercraft, lawn, and garden equipment. After rigorous analysis and extensive work with diverse stakeholders, EPA determined that such a strategy was feasible and safe.

These proposed rules also include the first ever:

• Fuel evaporative standards for all the types of equipment and watercraft covered in the rulemaking;

• Standards for vessels powered by sterndrive or inboard engines; and

• Carbon monoxide standards for gasoline-powered engines used in recreational watercraft.

With these proposed rules, nonroad gasoline-powered engines, such as those used in lawn and garden equipment, would see an additional 35% reduction in HC and NO_x emissions beyond a 60% reduction that finished phasing in last year under an earlier rulemaking. Those engines would also see a 45% reduction in fuel evaporative emissions.

Additionally, recreational watercraft can emit as much as 348 cars in an hour. By 2030, recreational watercraft powered by gasoline engines would see a 70% reduction in smog-forming HC and NO_x, a 20% reduction in CO, and a 70% reduction in fuel evaporative emissions.

The standards for these products have been combined into one proposal because these engines and vehicles share many common characteristics. However, differences in design and use led the EPA to propose separate emission standards for each group.

Small Nonroad Spark-Ignition Engines and Equipment. This category includes spark-ignition (SI) nonroad engines rated below 25 hp (19 kW) used in household and commercial applications, including lawn and garden equipment, utility vehicles, generators, and a variety of other construction, farm, and industrial equipment.

EPA is proposing HC+NOx exhaust emission standards for this group of 10 g/kW-hr for Class I engines starting in the 2012 model year and 8 g/kW-hr for Class II engines starting in the 2011 model year. EPA expects manufacturers to meet these standards by improving engine combustion and adding catalysts. These standards are consistent with the requirements recently adopted by the California Air Resources Board (ARB).

For spark-ignition engines used in marine generators, EPA is proposing a more stringent Phase 3 CO emission standard of 5 g/kW-hr. This would apply equally to all sizes of engines subject to the Small SI standards.

When fully implemented, the proposed standards would result in a 35% reduction in HC+NOx emissions from new engines’ exhaust. The proposed standards would result in a 45% reduction in evaporative emissions.

Marine Spark-Ignition Engines and Vessels. This category includes spark-ignition engines used in marine vessels, including outboard engines, personal watercraft, and sterndrive/inboard engines.

EPA is proposing a more stringent level of emission standards for outboard and personal watercraft engines starting with the 2009 model year. The proposed standards for engines above 40 kW are 16 g/kW-hr for HC+NOx and 200 g/kW-hr for CO.

For engines below 40 kW, the standards increase gradually based on the engine’s maximum power. EPA expects manufacturers to meet these standards with improved fueling systems and other in-cylinder controls. These standards also are consistent with the requirements recently adopted by California ARB.

EPA is proposing new exhaust emission standards for sterndrive and inboard marine engines of 5 g/kW-hr for HC+NOx and 75 g/kW-hr for CO starting with the 2009 model year. EPA expects manufacturers to meet these standards with three-way catalysts and closed-loop fuel injection.

To ensure proper functioning of these emission control systems in use, EPA is proposing a requirement that engines have a diagnostic system for detecting a failure in the emission control system.

For sterndrive and inboard marine engines above 373 kW with high-performance characteristics (generally referred to as “SD/I high-performance engines”), EPA is proposing a CO standard of 350 g/kW-hr. EPA is also proposing a variety of other special provisions for these engines to reflect unique operating characteristics and to make it feasible to meet emission standards using emission credits. These standards are also consistent with the requirements recently adopted by California ARB, with some adjustment to the provisions for SD/I high-performance engines and with a CO standard.

EPA is also proposing “not-to-exceed” standards that require manufacturers to maintain a certain level of emission control when engines operate under normal speed-load combinations that are not included in the certification duty cycle.

EPA is proposing new standards to control evaporative emissions for all vessels using marine spark-ignition engines. The new standards include requirements to control fuel tank permeation, fuel line permeation, and diurnal emissions, including provisions to ensure that refueling emissions do not increase.

When fully implemented, the proposed standards would result in a 70% reduction in HC+NOx emissions, and a 20% reduction in CO from new engines’ exhaust. The proposed standards would result in a 70% reduction in evaporative emissions.

When fully implemented, the rules would result in an annual emission reduction of 630,000 tons of HC, 98,000 tons of NO_x, 6,300 tons of direct particulate matter, and 2.7 million tons of CO.

The total estimated public health benefits of this rule are about $3.4 billion by 2030. These benefits would prevent 450 premature deaths, 500 hospitalizations, and 52,000 work days lost annually. When fully implemented, EPA expects that technology needed to meet the standards will have the added benefit of saving about 190 million gallons of fuel annually.

The estimated costs of the new standards range from $9.5 million in 2008 to $620 million in 2037. These control costs are partially offset by estimated annual fuel savings of about $360 million in 2037 once standards are fully implemented. As a result, the net cost of the program in each year ranges from $6.4 million in 2008 to $260 million in 2037.

The new standards would apply as early as 2011 for most lawn and garden equipment (under 25 hp) and 2009 for watercraft.

Comments on the proposal are due Aug. 3, 2007.

Resources:

• Proposed Emission Standards for New Nonroad Spark-Ignition Engines, Equipment, and Vessels