Fuel Consumption and Air Quality
By Dr. Kevin Robertson, Fire Ecologist
Getting accurate measurements of how much smoke and particulate matter is released from prescribed burning is increasingly important for guiding appropriate air quality regulations. One of the steps for determining particulate emissions from burning is estimating fuel consumption. The Fire Ecology Program has been measuring fuel consumption as part of various research projects, including the Stoddard Plots (1-4 year fire intervals), Pebble Hill Fire Plots (1-7 year fire intervals), Wade Tract burns, and research conducted with Florida A&M University, to study smoke emissions.
Federal and state agencies use computer models to estimate emissions from burning, but the models are only as good as they are accurate. We are working to test the accuracy of the commonly used models and to provide raw data to the modelers to help them make improvements. For example, our data will be provided to the Smoke Emissions Intercomparison Project (SEMIP), funded by the federal Joint Fire Sciences Program, which aims to compare and improve current computer models by collecting new data from participants such as Tall Timbers.
In the example below, our fuel consumption measurements are compared to those predicted by the First Order Fire Effects Model (FOFEM). Results show that fuel consumption predicted by FOFEM when burning 1 year after fire (1 year rough) are twice that of the actual amounts in native longleaf pine and old-field pine forests. However, for 2-4 year roughs the model predictions are about the same as the measured amounts on average. For all burns combined, fuel consumption was over-estimated by about 33%. Improving these models, and their estimates of particulate emissions, will help guide fair policies regarding the ability to use prescribed burning under air quality regulations.
Comparison of fine fuel consumption predicted by FOFEM vs. measurements in the field during prescribed burns. Circular symbols are burns in native longleaf pine-wiregrass forests and square symbols are burns in old-field shortleaf-loblolly pine forests. White symbols are 1-year roughs, gray symbols are 2-year roughs, and black symbols are 3-4 year roughs. The dashed line is the expected 1:1 relationship and the solid line is the regression curve for all burns together.