Reactive nitrogen (Nr) is a primary plant nutrient fertilizer that plays a critical role in agricultural production. For the past century, the availability of Nr in soil has become increasingly important to farmers as they attempt to grow the crops that contribute to nitrogen fixation, the process by which microorganisms convert nitrogen from the atmosphere into a form usable by plants.  

While the increased use of Nr has been effective in agricultural production, it has also contributed heavily to air pollution. In September, Sibeal McCourt, a PhD candidate in McGill’s Department of Geography, and Graham MacDonald, associate professor in the same department, published a study quantifying Canadian Nr emissions from food production and consumption, and comparing them to fossil fuel-related emissions. 

McCourt and MacDonald developed a national nitrogen footprint and more specific provincial metrics in order to gain a more nuanced understanding of each province’s contributions to Canada’s nitrogen emissions. These footprints look at virtual nitrogen factors (VNF), which refer to the total losses of Nr to the environment from the production of food.

The study accounts for Nr emissions released due to Canadians’ consumption and economic activities. They measured the total (in Gg Nr yr−1) and per capita (kg Nr capita−1 yr−1) N footprints for a three-year average in 2018, using a top-down approach that encompasses both individual consumption patterns and broader country-wide activities. The objectives of this study were to estimate the Canadian and provincial VNFs as part of the N footprint of food, study the driving factors in N emissions, and compare variations between provinces. 

“I found it surprising that fossil fuels could be the main contributor to N footprints in certain provinces,” McCourt said in an interview with The McGill Tribune. “Previous studies indicated that fossil fuels do contribute to N footprints, but the biggest source is from food consumption, particularly meat.”

Canada’s estimated total N footprint is 995.7 Gg Nr yr−1, with an average national per capita footprint of 27.1 kg Nr capita−1yr−1. The study revealed clear distinctions between provinces regarding total N footprints, per capita N footprints, and the main sources of Nr. For example, Prince Edward Island, with the smallest provincial population, produced 3.5 Gg Nr yr−1 and Ontario, with over 14 million people, produced 311.8 Gg Nr yr−1. Ontario’s per capita footprint clocked in at 22.0 kg Nr capita−1; however, Saskatchewan’s was by far the largest at 50.3 kg Nr capita−1 yr−1. This is due to Saskatchewan’s reliance on the production and use of fossil fuels for energy and because much of the province’s land is dedicated to commercial agriculture. McCourt and MacDonald found that the major drivers across all provinces were wastewater treatment, beef consumption, and transport. 

“Canada produces and exports a lot of food and fuel, and we also consume a relatively large amount of resources per capita,” McCourt said. “Having a better understanding of how both of these types of activities impact our environment will improve our sustainability.”

This research was conducted as part of McCourt’s PhD project, and the findings from this study will be used to further her research into emissions accounting in Canada. McCourt hopes to compare Canada’s reported provincial and national N emissions to the results she has come up with, and see what this could mean for the future of sustainable policy development.

“Hopefully this information will improve Canadians’ awareness of their environmental impacts,” McCourt said. “It’s important to hold companies and governments responsible for their environmental impacts so that we as consumers have more sustainable options available to us.”