Utilizing Fire Radiative Energy to Predict Organic Carbon and Elemental Carbon Emissions from Burns under Simulated Prescribed-fire and Wildfire Conditions
ROBERT PENLAND, Chase Glenn, Omar El Hajj, Anita Anosike, Kruthika Kumar, Steven Flanagan, Mac A. Callaham, E. Louise Loudermilk, Joseph O'Brien, Rawad Saleh, University of Georgia
Abstract Number: 322
Working Group: Combustion
Abstract
The Georgia Wildland-fire Simulation Experiment (G-WISE) involved performing burn experiments of fuel beds collected from 3 ecoregions in the Southeastern U.S.: Piedmont, Coastal Plain, and Blue Ridge. The Blue Ridge fuel bed contained surface fuels (fine and woody) and a duff layer, while the others contained surface fuels only. The fuels were conditioned to moisture contents representative of either prescribed fires (Rx) or drought-induced wildfires (Wild). Here, we present elemental carbon (EC) and organic carbon (OC) emissions and how they correlate with fire radiative energy (FRE) and FRE normalized by fuel mass loading (FREnorm).
For burns that involved ignition of surface fuels only, fuel consumption was linearly correlated with FRE (R-square = 0.90). However, burns that involved duff ignition fell outside the correlation (lower FRE for the same fuel consumption), indicating that duff exhibits less efficient combustion than surface fuels. Whereas OC emissions were linearly correlated with FRE for all burns (R-square = 0.73), EC emissions were linearly correlated with FRE (R-square = 0.72) for burns that involved ignition of surface fuels only. Again, burns that that involved duff ignition fell outside the correlation (lower EC emissions for the same FRE). EC/OC ratio was linearly correlated with FREnorm (R-square = 0.57), indicating that FREnorm is a practical metric for combustion conditions. FREnorm (and EC/OC) was lowest for burns that involved duff ignition. For burns that involved ignition of surface fuels only, FREnorm was lower for Rx compared to Wild.
Overall, these findings signify the importance of both moisture content and existence of duff in dictating combustion conditions and consequently, OC and EC emissions. Furthermore, the findings demonstrate the utility of FRE and FREnorm to determine OC and EC emissions, which can be applied in top-down emission inventories that rely on FRE retrievals from satellite observations.