We know it’s possible to fight fire with fire - it’s the principle of the counter-fire used to fight forest fires - but the idea of fighting fire with wood is not only counter-intuitive, it’s downright mind-boggling. However, if the results of Maxime Parot’s laboratory work are confirmed on a larger scale, we could one day see seaplanes dropping a gel made from molecules extracted from wood on the edge of forest fires to stop them spreading.
The postdoctoral fellow, a member of Alexis Achim’s team in the Department of Wood and Forest Sciences, presented the results of his work evaluating the effectiveness of a gel based on wood-derived molecules in fighting forest fires at the Faculty of Forestry, Geography and Geomatics Faculty Colloquium, held on campus on November 21 and 22.
This gel is made up mainly of water and cellulose, a polymer that represents around 50% of the mass of wood and which, in its natural state, is a fuel," recalls Maxime Parot. "More precisely, we use cellulose filaments that can be up to a few millimeters long, but only a few nanometers in diameter. The three-dimensional network formed by these filaments captures water molecules, delaying the gel’s combustion. In addition, we add an agricultural fertilizer, diammonium phosphate, which slows down the chain reaction that occurs when combustion takes place."
To evaluate the effectiveness of this gel, the postdoctoral fellow exposed small samples (10 cm X 10 cm X 1 cm) of black spruce to a 35 kW/m2 heat source. "Without gel, the wood catches fire after 40 seconds. When gel is applied to the wood, it takes a further 6 minutes for the wood to ignite. What’s more, the heat released by wood ignition is 44% lower than in tests carried out without gel. By adding lignin, another molecule present in wood, to our gel, we reduce the heat produced by 75%."
For a forest fire to start and spread, four conditions must be met, continues Maxime Parot. "You need fuel, oxygen, heat and a chain reaction. The gel we’ve developed prevents the fire from reaching the fuel (the wood), blocks the passage of oxygen, reduces heat production and slows the chain reaction thanks to diammonium phosphate. It therefore acts on the four elements essential to forest fires."
"Certainly it costs more than water, but you have to consider the savings that would be made by better protecting human infrastructure and forests."
-- Maxime Parot, about the gel made from cellulose There’s still a lot of work to be done to take this idea from the lab to the field, admits the postdoc. "First I need to do tests on larger wood samples using higher temperatures, to replicate what happens in the field when there’s a forest fire."
The economic analysis also remains to be done. "There’s no doubt that it costs more than water," he admits, "but you have to consider the savings that would be made by better protecting human infrastructures and forests." Savings that could rise rapidly given the increased frequency and intensity of forest fires expected as a result of climate change.
