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What is Retrofit?

Diesel engines are important power systems for onroad and offroad vehicles. These reliable, fuel-efficient, high torque engines power many of the world’s heavy-duty trucks, buses, and nonroad vehicles. While diesel engines have many advantages, they have the disadvantage of emitting significant amounts of particulate matter (PM) and the oxides of nitrogen (NOx) into the atmosphere. Diesel engines also emit toxic air pollutants. Health experts have concluded that pollutants emitted by diesel engines adversely affect human health and contribute to acid rain, ground-level ozone and reduced visibility. Studies have shown that exposure to diesel exhaust causes lung damage and respiratory problems and there is increasing evidence that diesel emissions may cause cancer in humans.

Companies that manufacture emission controls have responded to the challenge of reducing the air pollution from diesel engines. Through their efforts, cost-effective retrofit technologies have been developed to reduce harmful emissions. Within the various mobile source sectors (e.g., mining and materials handling, trucking, urban bus and school bus, ports, and construction), diesel retrofit technologies have demonstrated their ability to significantly reduce unwanted emissions at reasonable costs without jeopardizing vehicle performance.

Both the U.S. EPA and the California ARB have created diesel retrofit verification programs as a means to thoroughly evaluate the PM emission reduction capabilities and durability of a variety of diesel emission control strategies. Verification ensures that emission reductions achieved by a control strategy are both real and durable and that production units in the field are achieving emission reductions which are consistent with their verification.

Diesel Emission Reduction Strategies

Retrofit

Typically, diesel retrofit involves the addition of an emission control device to remove emissions from the engine exhaust. Retrofits can be very effective at reducing emissions, eliminating up to 90 percent of pollutants in some cases. Some examples of emission control devices used for diesel retrofit include diesel oxidation catalysts, diesel particulate filters, NO_x catalysts, selective catalytic reduction, and exhaust gas recirculation. Devices to control crankcase emissions also exist.

Repower

Repowering involves replacing an existing engine with a new engine. This strategy is most effective for use in diesel-powered equipment with a useful life longer than that of the engine. Repowering provides an opportunity to install a new engine (or a new engine equipped with exhaust emission controls) that meets much lower emission standards than the original engine, often in conjunction with fuel economy benefits and lower maintenance costs. Repowering can also include converting diesel-powered equipment to electrical power.

Rebuild

All diesel equipment requires periodic maintenance. Routine maintenance and repairs help to ensure that engines operate at maximum performance and emission rates do not exceed the designed standard. Major maintenance intervals provide an opportunity to have the engine rebuilt using more modern, cleaner parts and exhaust emission controls that provide an immediate emission reduction benefit.

Refuel

A variety of alternative fuels can be used in diesel engines. Some require little or no modification to the engine while others require engine conversion or replacement. Some of the alternative fuels include emulsified diesel, biodiesel, natural gas, propane and ethanol. In addition to these fuels, use of diesel fuel with lower sulfur content can help to reduce emissions.

Replace

Replacement involves retiring higher polluting equipment from service before it would otherwise be retired. Newer equipment that meets more stringent emission standards is purchased to replace the retire equipment, sometimes in conjunction with retrofit devices or alternative fuels.