A Closer Look At Biodiesel Emissions

Filed by Erika Engelhaupt

The scientists who came together this week in Brazil work in many areas of chemistry, as well as engineering, agronomy, and plant genetics. But I noticed that they were united not just by an interest in biofuels, but also by an ideal of sustainability. Whether they were discussing green chemistry or improving feedstocks, they were enthusiastic about using renewable resources in a sustainable way.

I don’t know whether everyone here would label themselves as an environmentalist, but this is certainly an environmental ideal.

One aspect of this sustainable vision is for biofuels to provide not only a carbon-neutral but also a clean, nonpolluting source of energy. To achieve this goal, scientists need to first understand how the pollution created by burning biofuels differs from that created by petroleum-based fuels. Then, those emissions must be minimized.

lilian.jpgOne enterprising Ph.D. student in Brazil is working on this issue by measuring the emissions produced by a variety of biodiesel blends. Her work earned special recognition in a student poster competition here at the symposium.

Lílian Lefol Nani Guarieiro, a Ph.D. student at the Universidade Federal da Bahia, won with her poster, “Determination of C1-C4 Carbonyl Compounds from Car Engine Exhaust Using Biodiesel/Diesel Mixtures.” She is shown in the photo to the left with her poster, which was selected from among those submitted by graduate students from Brazil at the poster session Wednesday night.

Guarieiro is the Brazilian half of a pair of graduate students who will begin developing their own international collaborations. Dante Simonetti was selected as the American student, and he claimed as his prize the chance to attend this tour and biofuels symposium (see Steve’s entry, “Dante’s Catalysis”).

Guarieiro and her graduate adviser, Jailson Bittencourt de Andrade (shown in the photo below), will receive a trip to attend the ACS national meeting in Boston this August, paid for by Bradley Miller’s National Science Foundation Discovery Corps project. There, they will present the poster at a biofuels symposium and will be recognized at a dinner hosted jointly by the petroleum and fuels divisions of ACS.


Guarieiro’s project examined aldehyde emissions from various biodiesel blends made from soy oil. She found that some emissions tripled when the percentage of biodiesel in a blend was 20% or greater. Acrolein and acetaldehyde emission levels increased significantly, and formaldehyde also showed this pattern. Propanol and butanol had smaller increases.

The results point to an important issue, Guarieiro says, because these emissions could adversely affect air quality. The volatile organic compounds can contribute to smog formation, and formaldehyde and acrolein are mutagenic.

Most surprising was how abruptly emissions increased at the 20% blend ratio (see figure below) compared with blends containing 10% biodiesel or less. The chemistry behind the sharp increase is not entirely clear, but Guarieiro and de Andrade point out that biodiesel contains fatty acids that are absent in petroleum diesel, and this leads to different chemical reactions in various blends.


The project focused on emissions that are unregulated in Brazil and in much of the world. “We need to investigate this more,” Guarieiro says. She is currently studying other biodiesel blends made with sunflower and castor oil, and her next step will be to study the chemistry behind the pattern she observed. She hopes to eventually find ways to reduce emissions, perhaps by improving catalysts for biodiesel systems.

“She’s doing work that is extremely important for the development of biofuels,” says Edwin Olson, a biofuels chemist from the University of North Dakota and one of the judges. Also judging the competition were Dante Simonetti of the University of Wisconsin, Madison, and Kathleen Hapeman of the U.S. Department of Agriculture.

Congratulations, Lílian!

4 Responses to A Closer Look At Biodiesel Emissions

  1. Andres C. says:

    I’d like to know more about these emissions;
    does it means that biodiesel represents more air contamination?
    can we use biodiesel in motors anyway?

  2. jeff says:

    Your contribution to the subject of biodiesel emissions is vital to the further development of safe and environmentally sound protocols. I too am currently developing HC and particulate traps that should reduce NOx output. I am an undergraduate working toward a BS in engineering. Any info on further developments would be greatly appreciated in Northern California. The goal here is also to educate and successfully curb a potential landslide of pollution produced by biofuels.

  3. Buzz Lynds says:

    We have heard of the increased emissions from biofuels, and your findings are indeed striking. We have been working on emission reduction from another angle, making the fuels more combustible whereby not only decreasing exhaust emissions, but increasing efficiency. We have also tested with biodiesel and saw similar results. Thank you for your work and we look forward to hearing more from your research.

  4. Biodiesel fuels have an almost unlimited resources base for production.

    While the creation of biodiesel may have begun with experiments into the use of corn and soybeans, today’s technology goes far beyond that. We can use the virgin oils created by all sorts of different plants, many of which we use in our kitchens today.

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