Biomass Burning Emissions - Composition, Uptake, and Evolution
Creators: Loebel Roson, Max
Publisher: name: University of Alberta Library
Year: 2023

<p>Biomass burning, from wildfires to cooking stoves, is a major contributor to atmospheric pollution on a global scale, affecting the quality of the air we breathe. Emissions from biomass burning are both health and climate affecting, and vary considerably in composition depending on how the fuel is burned. Currently, millions depend on biomass fuels for energy production, cooking, and heating purposes. And yet, we still do not fully understand the composition of biomass burning emissions, their evolution once travelling through the atmosphere, or their impacts. The effects of biomass combustion are compounded for people living in developing regions such as Sub-Saharan Africa, where reliance on unrefined biomass like wood or cow dung is widespread. Usage of unrefined fuels and inefficient stoves aggravates the impacts of biomass burning; impacts which can only be accurately predicted with a comprehensive understanding of emission composition. The matter is also urgent, considering that wildfire incidence and severity is expected to rise in the coming years.</p>

<pre><code>The goal of this thesis is to forward our understanding of biomass burning emissions from understudied fuels, from composition to evolution in the atmosphere. In Chapter 2, I discuss the composition of biomass burning emissions through the study of wood and cow dung fuels combusted in a tube furnace capable of highly reproducible burns. I report that the composition of the base fuel directly impacts that of the emissions, which for dung comprise a complex matrix of light-absorbing and nitrogen-containing compounds. Additionally, I detail that levoglucosan and its isomers galactosan and mannosan - tracers generally used to source-apportion wood burns - are also emitted from burning cow dung, and report their emission factors. I conclude that the effects of biomass burning in regions which rely on dung fuels could be underestimated. And, that on a per-mass basis, the climate impacts of dung burning are likely greater than wood.

In Chapter 3, I apply novel analytical and statistical techniques to the study of biomass burning emissions. Here, I describe which burn parameters, such as heating temperature, air flow rate, or fuel type, contribute to altering the composition of the emissions. This was achieved through the coupling of two-dimensional gas chromatography mass spectrometry (GC×GC-MS) and principal component analysis (PCA). While GC×GC-MS separates the emissions, PCA identifies which components are characteristic to each burn parameter. I report that the major driver for differentiation between emissions are flow rate and temperature. As well, I show that low flow rate combustion of cow dung is associated with more diverse emissions, including health-affecting furans and thiazoles. This chapter demonstrates that coupling GC×GC-MS and PCA can effectively deconvolute biomass emissions too convoluted to otherwise characterize; a combination of techniques which has not been applied to the study of biomass burning emissions in a laboratory setting previously.

In Chapter 4, I focus on the evolution of anhydrides in the atmosphere. Specifically, I discuss how anhydrides can reactively uptake to the surface of biomass burning emissions, and report the uptake coefficients of phthalic anhydride under increasing loading masses. I detail how electrophilic anhydrides can react with a variety of nucleophiles present in biomass burning emissions to form larger water-stable products, including with the tracer levoglucosan. This mechanism might explain how volatile compounds like anhydrides end up irreversibly partitioned to the particle-phase in the atmosphere, improving our understanding of the evolution of burn plumes.

Overall, this thesis provides novel data and methods for the study of biomass burning and its emissions. The information provided within will help differentiate emissions from previously understudied biomass fuels, and ultimately, aid in the creation of atmospheric models to predict the impacts of biomass burning.
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