The trucks will have a Selective Catalytic Reduction (SCR) system which uses liquid urea to reduce oxides of nitrogen (NOx) emissions by as much as 75% without decreasing fuel economy.
The aqueous urea -- a reducing agent -- is injected into a 120-pound catalyst mounted behind the cab in the exhaust flow. Inside the catalyst, a chemical reaction reduces a significant portion of the NOx to nitrogen and water vapor. Injection is managed by a controller connected to the diesel engine's electronic control unit. The urea is a clear liquid which is non-flammable, non-toxic, and non-hazardous liquid is contained in a 30-gallon tank on the truck.
The SCR technology is the SINOx system developed by Siemens-Westinghouse. It has already been tested extensively in Europe on Mercedes-Benz and MAN trucks.
The California demo is expected to begin in late spring and run for three years or 500,000 miles, whichever comes first. The trucks are spec'd with 12-liter Detroit Diesel Series 60 engines and have a special 30-gallon compartment for urea built into the fuel tank.
The trucks will be owned and operated by flatbed fleet Valley Material Transportation, Inc. of French Camp, CA. By evaluating the SCR system in normal operating conditions, Freightliner hopes to assess the potential of the catalyst under real-world circumstances.
In addition to emissions, fuel economy and durability testing, the Institute of Transportation Studies at the University of California-Davis will conduct a comprehensive study to investigate trucking industry acceptance, infrastructure needs, technical feasibility and the cost-effectiveness of the system. The systems installed on the test vehicles cost around $30,000, but Freightliner expects production versions to be closer to $2,500.
Urea is commonly used on farms as fertilizer, so some tanks already exist. But additional filling stations would need to be installed around the country to make the SCR system feasible.
Clean air agencies including the California Air Resources Board, the San Joaquin Unified Air Pollution Control District, and the Sacramento Air Pollution Control District are helping to pay for the demonstration.
Freightliner is working on a number of other research projects in emissions reduction. The company already offers a line of alternative-fuel commercial vehicles, including trucks powered by propane, liquid natural gas (LNG) and compressed natural gas (CNG).