(adapted from MacRae et al., 2013)
The food system is a bigger contributor to GHG emissions than most decision makers recognize (30-34% of total consumption impacts [EC 2006] or total anthropogenic emissions [Vermeulen et al. 2012], see also Crippa et al., 2021). This makes the food system the greatest contributor to GHG emissions on the planet. Equally significant, such emissions do not always occur where analysts think and that means interventions to reduce emissions may be misdirected.
Canada, similarly to many industrial countries, does not actually collect food system emissions. It partially accounts for agricultural emissions, but those associated with other parts of supply chains are lumped into broader categories (e.g., manufacturing, retailing, household, waste). Creating a coherent picture, then, of food system emissions is a challenge and relies on triangulating data from numerous sources.
Although the public focus has been on food miles, several studies suggest that transport is not a main source of energy inefficiencies and emissions, with that honour going to agricultural production, processing and consumption (Kramer 2000; Weber and Matthews 2008; Foley et al. 2011; Garnett 2011).
Agriculture is certainly a significant contributor to Canada's total emissions. It accounts for at least 8% of national emissions and there has been a 21% increase in emissions since 1990. It is responsible for 70% of total national nitrous oxide emissions and 27% of total national methane emissions (National Inventory Report 1990-2014, exec summ). The big drivers are: N fertilizer manufacturing and use, and livestock populations and densities and livestock feed. All these emissions are underestimated because Canadian analysts have not conducted a full life cycle assessment of the agricultural sector.
Other sectors of the food system are also important contributors. Canada relies excessively on trucks to move domestically animal products, fruits and vegetables, and many grocery items and to and from the US and these are one of the least efficient modes of transport (Edwards-Jones et al., 2008), accounting for 10-20% of total food system emissions. The food system runs on heating and cooling motors and many of these are old and energy efficient (Garnett, 2006), accounting for 8-16% of food system emissions. Food processors emit significant levels of carbon dioxide associated combustion (most processed foods are cooked in some form), accounting for 10-20% of emissions. High levels of food waste across the food system generate significant emissions in two ways: first the energy embodied in the food is wasted with the food itself; and then there are significant emissions associated with waste handling and disposal (MacRae et al., 2016). The consumer end of the supply chain may account for 20-30% of emissions when waste is included, but this estimate is complicated by the reality that the cause of food waste is not the same as where it happens (see Food Waste, this section, and Goal 5, Reducing Food Waste).