Using a $1 million grant from the U.S. Environmental Protection Agency, the Texas Diesel Testing and Research Center at the University of Houston will retrofit school buses with a system that attempts to diminish the negative impact their diesel emissions can have on the environment.
UH researchers will supervise the installation of Nett Technologies’ BlueMAX Selective Catalytic Reduction System on 10 area buses. Then, over the course of the next two years, they will analyze the system’s ability to reduce smog-causing Nitrogen Oxides (NOx) and sooty particles being released through emissions using a series of real-world tests.
“Retrofits are a cheaper alternative to completely replacing dirty diesel engines that contribute to non-attainment areas, such as Houston, being unable to meet air quality requirements,” said Rachel Muncrief, the lead investigator on the grant and a research assistant professor of chemical and biomolecular engineering at UH. “The EPA is responsible for verifying the efficiency of retrofits before giving their approval for them to be utilized to get emissions credits. In-use testing projects such as these are an important part of the EPA’s decision-making process when evaluating whether a technology should be verified.”
Evaluating retrofit devices has been a focus of UH’s diesel center since its 2003 start. The EPA will use their data on this emerging technology, set to be verified next month, to determine whether its scope of verification can be expanded, said M.A. Mannan, business manager for Nett Technologies.
“This testing could allow more engines and types of vehicles to be included in our verification,” said Mannan from the company’s Ontario, Canada headquarters. The diesel center is already in the process of testing five non-road construction vehicles using the same NETT system.
Just as they initially did with the off-road construction vehicles, researchers will conduct a series of baseline tests to determine the level of pollution created by the buses prior to retrofitting. Once complete, the system will be installed.
It is designed to convert NOx not only into water, but nitrogen gas—a naturally occurring substance in the air we breathe—by adding a reductant, in this case urea, to the exhaust stream. Sensors measure the amount of NOx present in the exhaust stream and determine the quantity of urea needed to produce a chemical reaction that reduces the NOx as it passes over the catalyst, thus releasing a smaller amount of toxins into the environment.
At least twice during the study, they will conduct on-road tests using their portable emission measurement system as well as hook the buses up to their chassis dynamometer. This kind of treadmill for vehicles will allow researchers to measure emissions in house. Both tests will help them to determine just how close the system can come to reducing NOx as well as particulate matter and other pollutants produced by the buses.
“Houston has a high population density, poor air quality and is in an ozone non-attainment area due, in large part, to the significant amount of NOx emitted by diesel powered vehicles and equipment,” Muncrief said. ”Retrofits have the potential to significantly reduce the total annual NOx emissions in the area.”
Muncrief will work with diesel researchers Michael Harold, professor of chemical and biomolecular engineering, and Charles Rooks, director of the diesel center, on the project.