Greenhouse Gas Emissions From Fire

Reliable estimates of carbon emissions from planned and unplanned fires are required to assess the impact of smoke on the atmosphere.

This research by Dr Tina Bell and Dr Malcolm Possell, both from the University of Sydney, aimed to further develop knowledge of greenhouse gas emissions from fuel reduction fires and their potential impacts on the carbon balance of forested ecosystems.

The research involved the development of a new laboratory method that can detect and measure a range of emissions from burning vegetation. The program was initially planned to determine the role of one of the most important components of fire behaviour – fuel moisture content – on smoke emissions and fuel flammability.

Findings showed that vegetation containing more moisture produced less carbon dioxide and more carbon monoxide than drier vegetation, and that none of the gaseous components of bushfire smoke that were measured using the experimental setup were produced in toxic quantities. The differential emissions recorded from wet and dry fuels could provide a mechanism for fire managers to manipulate the emissions from planned burns in the future. The study also showed that an introduced weed, African lovegrass, was much more flammable than the native Australian grasses.

Testing of several species of eucalyptus showed limited differences in flammability attributes or carbon emissions among species, but there were greater differences detected among tropical and savanna grasses, providing some boundaries to the level of generalisation that can be made.

This project has improved the understanding of the relationships among fuel type and condition and burning conditions on emissions of gases, and will help advise how best to manage fires to minimise their ecological and economic impacts. This is an important area to investigate as the carbon costs of fuel reduction fires are yet to be determined and will likely have considerable economic value in future.

Three postgraduate students at the University of Sydney were also connected to this study. Vicky Aerts’s PhD looked at how smoke from prescribed burning and bushfires affected agricultural and native plant physiology. She tested the effect of smoke from Sydney Blue Gum (Eucalyptus saligna) leaves on strawberry plants, finding that it had only a temporary effect and the plants fully recovered.

Felipe Aires investigated the leaf traits and combustion features of invasive woody plants in forests of eastern Australia, focusing particularly on olives. His research will help decision makers take the right course of action when fighting fires in invaded areas.

The PhD work of Valerie Densmore explored how woody legumes, typified by wattles, can play a central role in restoring ecosystems following bushfires. She showed that when their seeds are exposed to heat they germinate quickly, helping to stabilise soil and return nitrogen to the system. The knowledge gained from her research is important to predicting ecosystem resilience and fuel recovery following fire.