Contract sweepers have likely heard about the Environmental Protection Agency's (EPA) emission regulations, but regulations taking effect in 2010 will have an impact on the trucks you buy and, at least in California, on the trucks you already own.
Finalized in 2001, the EPA's Highway Diesel Rule required that harmful pollutions from engines be reduced by more than 90% beginning with 2007 model year engines. For 2010, the EPA will tighten the emissions standard by requiring new diesel engines to emit no more than 0.2 grams of nitrogen oxides per horsepower-hour.
In order to comply with EPA regulations, engine manufacturers are incorporating one of two technologies in their new engines: Selective Catalytic Reduction or Exhaust Gas Recirculation. Most engine manufacturers are using Selective Catalytic Reduction technology in their engines, says Brian Giles of Elgin Sweeper.
Selective Catalytic Reduction
Selective Catalytic Reduction (SCR) is a technique for reducing nitrogen oxides (NOx) by injecting a fine mist of urea plus water through a catalyst into the engine's exhaust stream. This creates a chemical reaction turning the nitrogen oxides into nitrogen and water vapor. When heated during the SCR process the urea mix, also called diesel emission fluid or diesel exhaust fluid (DEF), turns into ammonia and carbon dioxide. These by-products, natural elements of the air we breathe, are then discharged through the tailpipe.
With SCR the nitrogen oxides reduction process takes place after combustion. Some of the benefits SCR is said to have include: enhanced thermal efficiency and fuel economy, reduction of heat rejection and cooling system stresses, and possible emissions reduction up to 90%.
Because SCR requires the use of urea, trucks with this technology will require an onboard tank to hold the urea. Failure to maintain this tank and urea levels might result in a reduction in torque output for the sweeper.
EPA mandates that engine manufacturers limit the vehicle speed to 5 mph if the system detects any attempt to tamper with or defeat the system, says Charlie Cox, an emissions technology consultant with Ironman and a speaker on this topic at the upcoming National Pavement Expo West, Dec. 3-5 in Las Vegas.
A nitrogen oxides sensor will also be needed to ensure the urea level is not neglected. The engine's computer management system will be able to detect "fake" diesel emission fluid, warn the driver when the diesel emission fluid level is low, and will disable the engine if it detects any attempt to tamper with or defeat the SCR system, Cox says. Urea freezes at 12°F, so trucks that operate in colder environments may also need heated storage for the urea tank.
Exhaust Gas Recirculation
Exhaust Gas Recirculation (EGR) technology recirculates exhaust gases back into the engine air intake cylinder and burns them again. EGR takes some of the exhaust gas from the diesel engine, cools it and blends it with fresh air, then recycles it back through the engine to dilute the amount of oxygen in the intake charge. This process reduces the temperature of combustion and lowers the formation of nitrogen oxides. The reduction in oxygen mixed with the use of cooled EGR can reduce emissions up to 90%.
EGR technology does not require any tanks to be added to a vehicle, but the addition of EGR coolers increases the overall engine size, and additional heat loads from the recycling and reburning of exhaust could increase the amount of cooling capacity required.
Effects on sweeping
So how do these new engine technologies affect contract sweepers? It depends on what type of truck you are running and whether or not you work in California. Twin-engine sweepers feature an on-highway engine in the front and an off-highway engine in the back. Since the front engine is an on-highway engine, it will need either SCR or EGR to comply with the 2010 regulations. However, the back, off-highway engine is less critical to the contractor at this point and will probably not need SCR or EGR technology until Tier 4 requirements in 2012, Giles says.