University of Rochester

Jesse L. Rosenberger Seminar Series

The Hidden Threat from Using Wood Pellets: CO off-gassing and the solution

Philip Hopke, PhD Adjunct Professor, Department of Public Health Sciences, University of Rochester Medical Center, Bayard D. Clarkson Distinguished Professor Emeritus, Institute for a Sustainable Environment and Department of Chemical and Biomolecular Engineering, Clarkson University

Friday, December 1, 2017
3:00 p.m.–4:00 a.m.
108 Goergen Hall, University of Rochester River Campus

UR photo


The off-gassing of carbon monoxide (CO) from stored wood pellets has been identified as a significant problem potentially resulting in adverse occupational and residential exposures. The mechanism for the production of CO from wood pellets has not been fully identified. In this study, a multiple step process has been hypothesized. The reaction is initiated by the autoxidation of unsaturated compounds including fatty acids and terpenes by molecular oxygen.  As a byproduct of these reactions, hydroxyl radicals are formed.  Then, the bulk of the CO results from the reactions of hemicellulose and hydroxyl radicals. To understand the mechanistic pathway of CO off-gassing, a number of experiments were conducted in which CO was measured and evolved organic compounds were analyzed using GC-MS. These studies identified a number of short and long chain aldehydes from the evolved gases that indicates the autoxidation mechanism. However, there is insufficient mass of these unsaturated compounds in wood to support the mass of off-gassed CO.  The role of hydroxyl radicals was investigated using a radical scavenger and its role in CO production was confirmed.  Thus, if the autoxidation initiation can be eliminated, then CO off-gassing from pellets would be substantially reduced.  Destruction of the reactive compounds with ozone led to a suppression of CO formation suggesting an approach to process the wood fiber that would result in low or no CO emission wood pellets. The process has now been tested at both laboratory and production scales and no-emissions pellets are now possible.


Dr. Philip K. Hopke is the Bayard D. Clarkson Distinguished Professor Emeritus at Clarkson University and Adjunct Professor in the Department of Public Health Sciences of the University of Rochester School of Medicine and Dentistry.   He was the founding Director of the Center for Air Resources Engineering and Science (CARES), and the Director of the Institute for a Sustainable Environment (ISE).  Dr. Hopke was the Chair of EPA’s Clean Air Scientific Advisory Committee (CASAC), President of the American Association for Aerosol Research (AAAR), and was a member of the more than a dozen National Research Council committees and a recent member of the NRC’s Board of Environmental Studies and Toxicology.  He is a fellow of the International Aerosol Research Assembly, the Association for the Advancement of Science and AAAR.  He served as a Jefferson Science Fellow at the State Department during the 2008-09. Professor Hopke received his B.S. in Chemistry from Trinity College (Hartford) and his M.A. and Ph.D. degrees in chemistry from Princeton University. He came to Clarkson in 1989.