Effect of Fuel Structure and Species on Grassy Fuel Ignition: Insights From Bench Scale Experiments and Thermogravimetric Analysis

Grassy vegetation represents a significant fuel source in multiple fire-prone regions around the globe. These fuels are a major component of surface fuel beds and are therefore typically the first layer of the wildland fuel strata that ignites. Thus, understanding the drivers of successful grassy fuel ignition is key to developing a comprehensive description of the process leading to fire spread. In the wildland-urban interface, hot metal particles produced by powerline failures or mechanical equipment operations are a leading ignition source for these types of fuels. The goal of this study is to develop improved understanding of the role of fuel species and physical characteristics on the ignition behavior of grass fuels when exposed to hot metal particles. Three common California invasive grass species were studied in their natural configuration as well as in configurations in which fuel particles have been shredded or made into a powder. Overall, it was observed that the ignition temperature was lower in fuels in their powder form than fuels in a shredded or natural form. Furthermore, the findings here align with prior works, indicating that the presence of chemical compounds such as lignin and proteins may hinder ignition. Consequently, wheatgrass fuels, which have higher lignin and protein content, consistently required higher temperatures to ignite (460°C) compared to Avena (370°C), Bromus (348°C), and excelsior fuels (350°C), which contain these compounds in lower concentrations.