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List of State Officials - Robert Ehrlich, Governor; Michael Steele, Lt. Governor; Kendl Philbrick, MDE Secretary 

Volume 2, Number 1

May 2006

eMDE is a monthly publication of the Maryland Department of the Environment. It covers articles on current environmental issues and events in the state. Additional monthly features include: MDE public meetings and hearings schedule, enforcement and compliance notes, and permitting activity. 

Diesel Retrofits Help Clean Regions' Air

By Lonnie Richmond

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Photo of exhaust system 

Photo of diesel engine 

Photo of exhaust system 

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Each day, tens of thousands of heavy-duty diesel vehicles travel Maryland roadways. These vehicles – tractor-trailer rigs, dump trucks, buses, and emergency equipment – emit large amounts of nitrogen oxides (NOx) and particulate matter (PM) into the region’s airshed. These diesel exhaust emissions pose risks to both human health and Maryland’s environment.

NOx is a precursor to the summertime problem of ground level ozone and also contributes to the nitrogen pollution to the Chesapeake Bay. Ozone pollution typically affects everyone in the same way, causing eye and throat irritation, coughing and difficulty with breathing. PM can be inhaled deeply into the lungs, causing lung tissue damage, impaired breathing and aggravation of respiratory illnesses. Exposure to PM can also cause adverse risks to the cardiovascular system including increased risk for heart attacks and cardiac arrhythmias.

However, there are positive changes on the horizon for our air quality. Starting with model year 2007, all new heavy-duty diesel highway vehicles exceeding 8,500 pounds (gross vehicle weight) must meet new federal emissions standards. The new vehicles will emit 90 percent less NOx and PM.

Millions of diesel vehicles produced before 2007, however will remain on our nation’s roadways over the next 20 or so years. These vehicles could continue to emit large amounts of air pollutants during their lifespan, but there is a solution. Making these legacy vehicles cleaner lies with four “Rs” – replace, repower, rebuild and retrofit.

Retrofit is Most Cost Effective
Replace (the vehicle), repower (a new engine), rebuild (the existing engine) are costly means of getting older vehicles to reduce emissions. The most cost-effective solution is to alter a vehicle with diesel retrofit technology equipment. Commonly used retrofit equipment includes diesel oxidation catalysts (DOC), diesel particulate filters (DPF), and closed crankcase ventilation filtration (CCVF) systems.

A DOC replaces a vehicle’s original muffler and is the most cost effective of retrofit equipment. These devices can greatly reduce vehicle emissions of PM, carbon monoxide and hydrocarbon. The cost of installing DOC equipment ranges from $900 to $1,500 per vehicle.

DPFs, also called PM traps, replace the original muffler of a vehicle, but are costly ($7,000 to $8,500) and require the use of use low-sulfur diesel fuel. These retrofit systems reduce PM emissions by 60 to 90 percent and carbon monoxide and hydrocarbon emissions by 90 percent. Beginning with 2007 model year vehicles, most diesel engines will have DPFs as standard equipment.

Crankcase filtration systems reduce the PM, carbon monoxide and hydrocarbon emissions that could potentially enter the driver and passenger cabin areas of the vehicle and also reduces engine oil consumption. These systems are relatively inexpensive with costs ranging from $750 to $1,000 per vehicle.

Funds Available
The Maryland Department of the Environment’s (MDE) Mobile Sources Control Program (MSCP) is actively promoting the use of retrofit technology. They discovered early on that many fleet managers were not aware of current diesel retrofit technology, or the fleet owners lacked funding to install the devices. MSCP campaigned to promote awareness of the technology through workshops, presentations and networking. MSCP also sought federal grants to help local fleets purchase and install retrofit technology.

One of MSCP’s first outreach efforts was holding a workshop two years ago for school bus fleet owners and operators. Today, MDE has 13 active projects with state, county, and municipal fleets. These projects are retrofitting school buses, transit buses, trash and dump trucks, ambulances and fire trucks.

Two of the larger projects involve retrofitting vehicles for the City of Baltimore and school bus fleets in central Maryland. The project for the City of Baltimore will retrofit 106 trash trucks and 23 dump trucks with DOC and CCVF devices by the end of this year.

School Bus Retrofit
Another large project involves 400 school buses operated by Anne Arundel, Montgomery and Prince George’s counties. These projects, slated for completion by the fall, will reduce student and operator exposure to several pollutants found in diesel exhaust.


©2006 Copyright MDE


Editorial Board
Maryland Department of the Environment
1800 Washington Boulevard, Baltimore, MD 21230