PhD Oral Defense of Patrick Brassard, Department of Bioresource Engineering
Like every sector of activity, the agriculture sector will need to develop and apply solutions to mitigate greenhouse gas (GHG) emissions in order to limit the temperature increase to 1.5 °C above pre-industrial levels, which was an objective stated in the Paris agreement in 2015. In the province of Quebec (Canada), agricultural soils generate 26.9% of the total emissions in the agricultural sector. Most of them are in the form of N2O emissions resulting from the nitrification and denitrification of mineral N. Research studies demonstrated that biochar amendment to soil can contribute to the reduction of GHG emissions, and particularly N2O. Biochar is the solid product of the thermochemical decomposition of biomass at moderate temperatures (350 – 700 °C) under oxygen-limiting conditions, which is generally achieved through pyrolysis. About 50% of the carbon (C) in biomass is found in biochar after pyrolysis, and most of this C would be sequestered in soil for more than 1000 years according to many researchers. However, not all biochars are created equal as their properties will depend on both biomass properties and pyrolysis operating parameters. Therefore, biochar with specific properties should be designed for a specific application. Soil properties and environmental conditions will also have an impact on the effect of biochar in soil.
The main objective of this doctoral research project was to produce engineered biochars with specific properties and to evaluate their potential to be used as a tool to mitigate climate change.