Keene State undergrads study biodiesel particulate toxicity

Two undergraduate research teams at Keene State College are studying the toxicity of biodiesel particulates from exhaust emissions and their impact on human health—research considered to be graduate-level work.

“We began this project using exposure as our measurement of health,” explained Associate Professor of Environmental Studies Nora Traviss. “We examined whether or not the pollution created by biodiesel combustion resulted in higher exposure for workers than the pollution created by petroleum diesel. It was very much an exposure assessment.”

Traviss and her research team mounted particle impactors in operators’ cabs in machinery at the Keene Recycling Center, collecting samples of both petroleum diesel and biodiesel exhaust. The impactors can separate out different sizes of extremely tiny particles, allowing researchers to see what the drivers are breathing—a real-world approach rather than laboratory simulation. “The exhaust we're collecting is diluted in the air, it's going through chemical reactions from the sunlight, and it's combining with other molecules in the air,” Traviss said. “We're studying the quantity of the particulate matter the driver is breathing and its unique chemical composition, which we hypothesize will be different from particles collected directly from the tailpipe.”

Her team found the amount of particulates in biodiesel exhaust is lower than those from petroleum diesel, but their chemical composition is different, raising another question: Are those particulates more toxic than their petroleum-based counterparts? Traviss refocused her research to look at toxicity rather than just exposure levels.

Traviss received a $400,000 grant from the National Institute of Health’s Academic Research Enhancement Award Program to continue her work, and assembled an interdisciplinary team to conduct the research, drawing in two environmental studies majors, Rachel Klaski and Tara Pratt; chemistry major Patrick Kelley; biology major, Andrew Bosco; and a research associate with a degree in biology, Nathan Martin. Traviss enlisted the help of Assistant Professor of Physics Steven Harfenist and Associate Professor of Chemistry James Kraly to do the work in-house and give more Keene State science students valuable research experience.

Harfenist is using a transmission electron microscope at Dartmouth College to get images of the particulates to determine the physical differences in size and shape of biodiesel and diesel particles.

“From the images, we can get information through statistical analyses of size and shape distributions regarding the way in which the particles were formed (directly from the combustion process and/or through aggregation), which tells us something about how well the fuel was burned as well as how the particulates can affect human lung tissue,” Harfenist explained. “The agglomerate particles are about 1-2 micrometers long, and the primary particles they are composed of are approximately 10 nanometers. Bombarding materials with electrons helps us image them, but also can cause the materials to give off x-rays characteristic to particular elements, so we’re interested to see what types of elements we can detect while imaging them. The TEM creates an electron beam that passes through a number of magnetic lenses and then passes through our sample, showing an image of up to one million times magnification.”

Kraly and his team of student researchers—chemistry major Mike Cavaccas, biology and chemistry major Niko Brown and chemistry major with emphasis on environmental studies Ethan Hotchkiss—analyze the particles for their chemical composition.

“Part of the challenge is the number of chemicals we are screening for,” Kraly said. “We're trying to measure as many as four- to six-dozen compounds from each filter—37 different organic acid constituents, and it requires a very systematic approach.” His team screens for four different classes of compounds—polycyclic hydrocarbons, fatty acid methyl esters, and hopanes/steranes—with a total of 69 standard chemicals.

“There are other people looking at biodiesel particulate matter, but they're mainly at the grad school level,” Traviss said. “We're doing everything we're doing with undergrads. The National Renewable Energy Lab finds it really interesting that we're doing this work at the undergraduate level, and we've collaborated with them on various analyses. A lot of researchers look at one aspect, but we're looking at the physical, the chemical, and the toxicological—all in one lab, which is also very unusual, and all within one school.”

Once Kraly’s team analyzes the chemical composition of the particulates, Traviss’ group takes the particles and runs toxicological tests. “We use epithelial cells from human lung tissue that we grow and culture,” she explained. “We dose the lung cells with different concentrations of the particles to see how it affects them. We really need to know the chemical composition to relate it to the results that we get in our cell studies, because, if we get results that say one fuel or the other is really toxic, we must determine which compound class is producing this toxicity. How does this play out in the real world? If we were to find out that one or the other fuel produces a certain chemical or effect that's toxic, this would help inform engine manufacturers that they should design their engines to reduce the particulate matter. Maybe they need to invest in more aftertreatment technologies to burn off such compounds as PAHs or fatty-acid methyl esters.”

Click here to view a chart on the analysis of organic compounds associated with biodiesel exhaust.