Greenhouse gas emissions from laboratory-scale fires in wildland fuels depend on fire spread mode and phase of combustion

Author:

Surawski, Nic; Sullivan, Andrew ; Meyer, Mick; Roxburgh, Stephen; Polglase, Phil

Date of Publication:

2015-05-13

Publication Type:

Journal Article

Journal Title:

Atmospheric Chemistry and Physics

Volume:

15

Issue:

9

Pages:

5259-5273

Abstract:

Experimental fires were conducted in a combustion wind tunnel facility to explore the role of fire spread mode on the resulting emissions profile from combustion of fine ( 6 mm) Eucalyptus litter fuels. Fires were burnt spreading with the wind (heading fire), perpendicular to the wind (flanking fire) and against the wind (backing fire). Greenhouse gas compounds (i.e. CO2, CH4 and N2O) and CO were quantified using off-axis integrated-cavity-output spectroscopy (off-axis ICOS). A dilution system was employed with the off-axis ICOS technique to prevent spectral broadening of the CO emissions peak and to enable simultaneous quantification of N2O and CO. The forward rate of spread was 20 times faster and the Byram fireline intensity was 20 times higher for heading fires compared to flanking and backing fires. Emissions factors calculated using a carbon mass balance technique (along with statistical testing) showed that most of the carbon was emitted as CO2, with heading fires emitting 17% more CO2 than flanking and 9.5% more CO2 than backing fires, and about twice as much CO. Heading fires had less than half as much carbon remaining in combustion residues. Statistically significant differences in CH4 and N2O emissions factors were not found with respect to fire spread mode. Emissions factors calculated per unit of dry fuel consumed showed that combustion phase (i.e. flaming or smouldering) had a statistically significant impact, with CO and N2O emissions increasing during smouldering combustion and CO2 emissions factors decreasing. Findings on the equivalence of different emissions factor reporting methods are discussed along with the impact of our results for emissions accounting. The primary implication of this study is that prescribed fire practices might be modified to mitigate greenhouse gas emissions from forested landscapes by the preferential application of flanking and backing fires over heading fires. Future research could involve wind tunnel testing with more realistic fuel architectures and could also quantify particulate emissions with different fire spread modes.

Publisher:

Copernicus GmbH

Keywords:

biomass burning, bushfire, combustion wind tunnel, flaming combustion, smouldering combustion, heading fire, flanking fire, backing fire.

Field Of Research:

Environmental Chemistry (incl. Atmospheric Chemistry)

DOI:

https://doi.org/10.5194/acp-15-5259-2015

URL:

Link to Publisher's Version

Identifier:

EP146683

Publication Sub Type:

Journal article - Refereed

Language:

English

Attribution Statement:

Surawski, Nic; Sullivan, Andrew; Meyer, Mick; Roxburgh, Stephen; Polglase, Phil. Greenhouse gas emissions from laboratory-scale fires in wildland fuels depend on fire spread mode and phase of combustion. Atmospheric Chemistry and Physics. 2015; 15(9):5259-5273. https://doi.org/10.5194/acp-15-5259-2015