Vehicle miles traveled (VMT) and population trends are the primary activity measures for estimating mobile source emissions. As seen here, historical growth is expected to continue for the foreseeable future in Texas.

As the old saying goes, you shouldn’t compare apples to oranges. But sometimes evaluating them together can yield interesting information about fruit in general — as long as there’s a valid way to accurately assess the two relative to one another.

Each of Texas’ 254 counties is different from the others, from highways to air quality. To protect the public health, the Federal Clean Air Act requires the Environmental Protection Agency (EPA) to set limits on the amount of certain air pollutants. Air pollution can cause various health threats, from simple throat inflammation to respiratory and cardiovascular disease. Areas that exceed EPA standards are said to be in “nonattainment.” These areas risk losing federal funding if they fail to demonstrate compliance within a given period of time.

The Texas Commission on Environmental Quality (TCEQ) is responsible for ensuring that Texas meets EPA standards, but until now, the agency had no way of reliably tracking air quality trends across the state. To support TCEQ, the Texas Transportation Institute (TTI) has created a first-of-its-kind methodology that allows the direct comparison of Brewster County, in arid West Texas, to Orange County on the mouth of the Sabine River.

“With the tool developed by TTI researchers, TCEQ can identify mobile source air quality trends that are county specific but methodologically consistent,” explains Dennis Perkinson, program manager for TTI’s Transportation Modeling Program. “In short, our model allows the agency to project the potential pollution in a specific county and then compare that county with others statewide.”

TTI created the methodology to cover all counties, whether they’re currently in nonattainment or not. The model covers 50 years, from 1990 to 2040, to capture data from both the early emissions control programs and the expected effects of new vehicle standards, as well as growth in the number of vehicles on the road. Researchers rely on actual or estimated vehicle miles traveled (VMT) as the primary activity measure for making predictions of on-road mobile source emissions. For future analysis years, VMT becomes a function of historical VMT and the population projections supplied by the Texas State Data Center.

“These analyses of long-term trends support a proactive approach to air quality management that can help preserve the environment and protect public health, from Houston to Wink, Texas,” says Perkinson. “Small towns and big cities — everyone wants clean air.”

The real value of the methodology is that it provides consistent estimates, which means better analysis is possible on a larger scale. And better analysis can lead to smarter policies for the Lone Star State.

“It is our hope that this analysis will make it easier for TCEQ to examine the big picture of air quality throughout Texas,” says Perkinson.

TTI Associate Research Engineer Joe Zietsman (right) is leading a research project aimed at converting landfill gas to fuel for refuse trucks in India.

The thriving province of Maharashtra is one of the most populous and prolific industrial centers in India. With a population of over 96 million residents, it is particularly vulnerable to energy demands and pollutant emissions. The Texas Transportation Institute (TTI) is currently leading an effort to evaluate the feasibility of using the gases generated by Maharashtra landfills as a fuel source for its refuse trucks and municipal buses. This research is being performed for the U.S. Environmental Protection Agency (EPA) in partnership with the National Environmental Engineering Research Institute (NEERI), Mack Trucks Inc. and the Texas State Energy Conservation Office (SECO).

“Energy scarcity in all forms is a big issue in India,” says Deputy Director and Head of NEERI Rakesh Kumar. “Any attempt to get energy sources, particularly from unconventional sources, is most welcome. Landfill methane and its use for buses or refuse trucks provide an example of closing the loop of energy generation and its use.”

The world’s primary sources of energy are conventional fuels such as oil, natural gas and coal. The most apparent negative impacts of these conventional fuels are global warming, poor air quality and adverse health effects. Considering the impacts of conventional fuels, and their finite availability, noncoventional sources of energy are under development throughout the world.

One such nonconventional alternative is using landfill gas as a liquefied natural gas (LNG) fuel source for heavy-duty refuse trucks. The process involves converting methane gas, which is naturally produced by landfills, into LNG using a sophisticated chemical process. This process has been used with success in a pilot application in Burlington, New Jersey. The research team is seeking a solution to the problem of how to trap the escaping methane from Indian landfills.

“Landfills in India are very different from the sanitary landfills in the United States in that they are open pits without any gas collection systems,” says Joe Zietsman, TTI associate research engineer and director of the Center for Air Quality Studies. “In the sanitary landfills here in the United States, we cover them and are able to recover the trapped landfill gas using underground piping systems.”

A refuse truck pulls up to an LNG fueling station.

The researchers are working on a design to capture the escaping methane by first gathering the refuse into a large pile, covering it with a thin membrane layer and finally collecting the gas using pipes inserted from above, as opposed to the conventional underground systems used in the United States. The captured landfill gas will then be “cleaned” through a sophisticated chemical process to produce the LNG that can be used as vehicle fuel. In addition to powering refuse trucks operating at the landfill, the LNG can also be used to power local bus fleets.

If implemented, this approach will provide the citizens of Maharashtra a cost-effective fuel source and cleaner skies. “Methane is a greenhouse gas that remains in the atmosphere for more than 10 years. It is also 20 times more effective as a greenhouse gas than carbon dioxide,” says Zietsman. “To be able to recycle this harmful gas into a clean-burning fuel is a win-win proposition for everyone.”

“The EPA’s Methane to Markets Partnership is an international initiative that advances cost-effective, near-term methane recovery and use as a clean energy source. The project initiated by TTI and its partners fits perfectly with the overall program, and we are very excited to see the results and hopefully move closer to implementation,” says Rachel Goldstein, EPA’s Methane to Markets contract manager.