New research by University of Utah chemical engineer Kerry Kelly and Chemical engineering faculty Dr. Geoff Silcox suggests that a wood stove emits 50,000 to 100,000 times as much direct particulate as a gas furnace, and 60,000 to 250,000 times as much of the volatile organic compounds that act as particulate precursors.

Utah’s Wasatch Front suffers from periodic episodes of poor air quality in the form of fine particulate matter (PM2.5) during winter-time pollution episodes (i.e., inversions). These episodes create significant health and quality-of-life concerns, particularly on days when the concentrations exceed the National Ambient Air Quality Standards. During the winter of 2013/2014 Salt Lake County exceeded EPA’s National Ambient Air Quality Standards for PM2.5 on 31 days.

In partnership with the Utah Division of Air Quality and the Environmental Protection Agency, two chemical engineering researchers, Kerry Kelly and Professor Geoff Silcox, used 4-years of PM2.5 composition data and source signatures together with multivariate data analysis techniques to identify the contributors to the Wasatch Front’s PM2.5. They compared their results to the Utah Division of Air Quality’s inventory, which is used to set state air quality policy, and their results suggested that the state inventory underestimated the contributions from wood smoke and cooking. Based on their results and newly released guidance from the EPA, wood burning is now estimated to contribute 5 – 10% to winter-time PM2.5 levels. Although burning wood is a less common method for home heating than natural gas, for the same amount of heat, it generates orders of magnitude of more pollution.

Their research, which was published in May in the Journal of the Air and Waste Management Association , has led to a lively debate about wood burning along the Wasatch Front. It has led to increased awareness of the importance of wood burning, legislation to help individuals who use wood as their sole source of heat convert to natural gas, and increased enforcement of existing wood-burning restrictions. Utah Division of Air Quality investigated 311 wood burning complaints in 2013/14 compared to 86 complaints in 2012/13. Governor Herbert even mentioned this study in his state of the state address. This awareness about sources of PM2.5 emissions will lead to better ways of controlling sources resulting in better wintertime air-quality along the Wasatch front.

View of Salt Lake City from Twin Peaks during an inversion, January 21, 2013 when PM2.5 concentrations in Salt Lake City were approximately 45 ug/m3 (National Ambient Air Quality Standards is 35 ug/m3).
Graph: Sources of PM2.5 on winter-time inversion days (2007 - 2011).  These results are the average of two different source attribution methods.
Graph: Sources of PM2.5 on winter-time inversion days (2007 – 2011). These results are the average of two different source attribution methods.

Photos provided by Kerry Kelly.