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The new paper helps define these risks by finding the network of chemical steps that take place when biofuels are burned. An invited overview for Angewandte Chemie, one of the world’s premier chemistry journals, the paper draws on landmark research conducted by Westmoreland and his co-authors from research institutions in the United States, Germany and China. “By studying individual chemicals that make up biofuels, we were able to explain what emissions result from burning real biofuels,” Westmoreland says. “We can measure the individual intermediates and chemical reactions, helping us craft models that reveal what chemicals are emitted, and in what amounts, by various biofuels. These models can be used to design new engines, new fuels and new policies that foster environmentally sustainable and efficient energy solutions. “This is important for regulation, where policy makers are weighing the environmental and health costs versus the energy benefits of different biofuels, but it is also essential to decision makers in the business community. Industry does not want to invest in developing biofuels and related technologies that can’t pass policy muster, and this research will help them make educated investment decisions.” The paper draws on information the researchers have collected about the chemicals produced when biofuels are burned, and how those chemicals change during the combustion process. These insights stem from the use of a novel experimental apparatus the researchers built at Lawrence Berkeley National Laboratory and a second system in Hefei, China - which provide unprecedented detail as to exactly what is happening at a molecular level when biofuels are burned. The paper, “Biofuel combustion chemistry: from ethanol to biodiesel,” is the featured cover article in the May 3 issue of Angewandte Chemie. The paper was co-authored by researchers from NC State, Bielefeld University in Germany, Cornell University, Sandia National Laboratories, the University of Science and Technology of China and Lawrence Livermore National Laboratory. The research was funded by the U.S. Department of Energy, the U.S. Army Research Office, and Deutsche Forschungsgemeinschaft, among others. NC State’s Department of Chemical and Biomolecular Engineering is part of the university’s College of Engineering.
DOE/Sandia National Laboratories - press release:
Biofuel chemistry more complex than petroleum
LIVERMORE, Calif. - Understanding the key elements of biofuel
combustion is an important step toward insightful selection of
next-generation alternative fuels. And that's
exactly what researchers at Sandia and Lawrence Livermore national
laboratories are doing. The journal Angewandte
Chemie devotes its May 10, 2010, cover to a paper co-authored by
Sandia's Nils Hansen and Lawrence Livermore's Charles Westbrook, which
examines the essential elements of biofuel combustion.
The paper, "Biofuel combustion chemistry: from ethanol to biodiesel,"
examines the combustion chemistry of compounds that constitute typical
biofuels, including alcohols, ethers and esters.
Biofuels, such as ethanol, biobutanol and biodiesel, are of increasing
interest as alternatives to petroleum-based transportation fuels.
According to Hansen and Westbrook, however, little research has been
done on the vastly diverse and complex chemical reaction networks of
biofuel combustion. In general, the term biofuel
is associated with only a few select chemical compounds, especially
ethanol (used exclusively as a gasoline replacement in spark-ignition
engines) and very large methyl esters in biodiesel (used as a diesel
fuel replacement in diesel engines). The biofuels are oxygenated
fuels, which distinguishes them from hydrocarbons in conventional
petroleum-based fuels. While much discussion
surrounding biofuels has emphasized the process to make these
alternative fuels and fuel additives, Hansen and Westbrook are the
first to examine the characteristic aspects of the chemical pathways
in the combustion of potential biofuels. In
collaboration with an international research team representing
Germany, China and the U.S., Westbrook, Hansen and former Sandia
post-doctoral student Tina Kasper used a combination of laser
spectroscopy, mass spectrometry and flame chemistry modeling to
explore the decomposition and oxidation mechanisms of certain biofuels
and the formation of harmful or toxic emissions. Hansen's experiments
were conducted in part at the Chemical Dynamics Beamline of the
Advanced Light Source at the Lawrence Berkeley National Laboratory.
To understand the associated combustion reactions and to identify
recurring reaction patterns, Hansen and Westbrook agreed, it is
important to study prototypical variants of potential biofuels.
Their study was funded in part by the Department of Energy's Office of
Science, which supports fundamental research, including research aimed
at understanding, predicting and ultimately controlling matter and
energy at the electronic, atomic and molecular levels in order to
provide the foundations for new energy technologies and to support DOE
missions in energy, environment and national security.
Abstract: Biofuels such as bio-ethanol, bio-butanol, and biodiesel are of increasing interest as alternatives to petroleum-based transportation fuels. Liquid fuels are likely to be necessary long into the future because of their portability and high energy density. Biomass-derived liquid fuels offer the long-term promises of fuel-source regenerability and reduced climatic impact. Current discussions emphasize the processes to make such alternative fuels and fuel additives, the compatibility of these substances with current fuel delivery infrastructure and engine performance, and the competition between biofuel and food production. However, the combustion chemistry of the compounds that constitute typical biofuels, including alcohols, ethers, and esters, has not received similar public attention. This review highlights some characteristic aspects of the chemical pathways in the combustion of prototypical representatives of potential biofuels. The discussion focuses on the decomposition and oxidation mechanisms and the formation of undesired, harmful, or toxic emissions, with an emphasis on transportation fuels. New insights into the vastly diverse and complex chemical reaction networks of biofuel combustion – a consequence of the inherent chemical functions of the fuels - are enabled by recent experimental investigations and complementary combustion modeling. Understanding key elements of this chemistry is an important step towards intelligent selection of next-generation alternative fuels.
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