PROJECT green fleet:  emission reduction

technologies and terms

There are many ways to upgrade or ‘retrofit’ a diesel vehicle. Technologies range in cost, level of maintenance required and emission reductions achieved. Below is a summary of pollution control technologies offered through Project Green Fleet. 

DIESEL RETROFIT

A diesel retrofit is any technology, device, fuel or system that when applied to an existing diesel engine achieves emissions reductions beyond what is currently required by federal regulations at the time of the engine's certification.

DIESEL OXIDATION CATALYST (DOC)

A DOC is a device that catalyzes a chemical reaction to reduce pollution from the tailpipe of a diesel vehicle. The DOC can be installed ahead of the existing muffler or as a unit combined with a muffler. Much like a catalytic converter on a car, once a DOC is installed, it rarely requires maintenance.

CLOSED CRANKCASE FILTRATION SYSTEM (CFS)

A crankcase filtration system (CFS) closes off the crankcase circuit by filtering engine blow-by gases and then returning the exhaust to the combustion cycle. It will reduce engine oil consumption (up to 6 gallons per year) and improves in-cabin air quality. A filter is replaced after 500 hours of operation or after each oil change, which is the only ongoing maintenance associated with this piece of equipment.

FUEL-OPERATED HEATER (FOH) 

A fuel-operated heater (FOH) is a small heater that is run as an alternative to the main bus engine. It prepares the engine to start and provides heat for drivers and passengers, and lowers emissions by reducing idling time and limiting fuel use.  

DIESEL MULTISTAGE FILTRATION SYSTEM (DMF)

The DMF uses a two-stage metallic filter to trap and reduce diesel particulate matter (PM), hydrocarbons and carbon monoxide. Each filter stage consists of alternating layers of a corrugated metal and a porous sintered metal fleece. The DMF is designed to be maintenance free, but must operate with a minimum exhaust temperature in order to be effective.

DIESEL PARTICULATE MATTER FILTRATION SYSTEM (DPF)

The DPF is a ceramic device that collects particulate matter in the exhaust stream and oxidizes it into less harmful components using the high temperature of the exhaust. DPFs reduce emissions of particulate matter, hydrocarbons, and carbon monoxide by up to 90 percent. While DPFs yield the highest emission reductions, they also have the highest level of maintenance and require periodic cleaning by a special machine. The frequency of cleanings depends on the ability of the exhaust temperature to be maintained over 200 degrees C. Lower exhaust temperatures result in more particulate matter accumulating on the filter instead of burning off.

AUXILIARY POWER UNITS AND GENERATOR SETS (APU/GS)

APU/GS devices supply cooling, heating, and electrical power to vehicles that would otherwise require the operation of the main drive engine. This reduces unnecessary idling while the vehicle is temporarily parked or remains stationary.

DIESEL ENGINE REBUILD

A diesel engine rebuild involves refurbishing an existing diesel engine to improve efficiency. Engine rebuilding can significantly reduce emissions in some cases.

DIESEL ENGINE REPOWER

A diesel engine repower is the replacement of an old engine with a new cleaner-running engine that is certified to a more stringent set of emissions standards.

BATTERY AIR CONDITIONING SYSTEMS (BAC)

A battery air conditioning system uses batteries to power and independent cooling system on long haul, Class 8 trucks. This system allows the vehicle operator to turn off the main diesel engine, using the BAC to keep the cabin cool and reduce emissions. Typically, a BAC is integrated with a fuel operated heater to also supply heating.

Technologies implemented by Project Green Fleet are verified by the U.S. Environmental Protection Agency or California Air Resources Board.

Participants

4,600 Cleaner Engines and Counting!

Project Green Fleet has installed pollution control equipment on thousands of Minnesota school buses, heavy-duty trucks, and other diesel vehicles.

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