There are many choices we can make to decrease our carbon and land footprints, and food is a big part of it – especially at Christmas

Comment: Did you know that food and agriculture make up 26 percent of global consumption-based greenhouse gas emissions? But not all foods are equally burdensome. Some foods, particularly those from cows, emit much higher levels of greenhouse gases than plant-based alternatives.

Meanwhile, many of these foods also take up more land to produce, and therefore put more pressure on habitat loss, ultimately driving biodiversity loss.

And while the planet continues to warm because of ineffective policy and a lack of political consensus, food remains one of the key components to change that lies very much in the hands of individuals in the global north.

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Using methods such as Life Cycle Assessment (LCA), environmental scientists are able to estimate the potential of lifestyle choices to affect global warming, biodiversity loss, and water depletion and contamination.

LCA allows us to create an inventory of environmental impacts linked to the flow of resources along a supply chain. For example, it can capture the extraction of mineral fertilisers and pesticides, energy, and water used for a farming operation; the materials used in packaging; the fossil fuels used to transport those farmed products to the consumer, including the energy to refrigerate and cook the food; and finally, the energy to transport any wastes to landfill or recycling centres.

Many of these activities are obscured from the consumer’s view, but with LCA the entire environmental footprint of the foods we eat can be estimated and communicated to help us make more informed choices.

With Christmas approaching many people around the world will be celebrating, eating richer and more environmentally burdensome foods. Researchers Dr Thomas Elliot, Leopold Wambersie, and Professor Annie Levasseur at École de technologie supérieure (in Montreal, Canada) estimated the relative environmental impacts we can expect to have from typical Christmas foods, along with some lower-impact alternatives.

First, we assessed an average omnivore diet, which emits 15kg CO2-eq per day while needing 16m2 per day of agricultural land to produce that food. Vegans or people on plant-based diets emit 5kg CO2-eq per day, and require around 5m2 per day of land. These rates are equivalent to 4kg CO2-eq and 5m2 per kg of food for the omnivore, and 2kg CO2-eq and 2m2 per kg of food for the vegans.

Then we considered what types of festive foods people eat during Christmas, such as roast ham, turkey, pork pie, and fruit cake. We also considered a vegan roast Wellington, a vegetable pie, and a vegan Christmas cake.

Climate change and land use footprints of Christmas foods

All these dishes have higher impacts than the entire daily average for a person eating a typical omnivore diet, confirming the foods people eat during Christmas push our environmental footprints up. The carbon footprint and land use are linearly correlated; more land used generally means more greenhouse gas emissions. For instance, the roast ham emitted more than three times the carbon than the vegan Wellington and used more than 4.5 times the land area. In fact, the roast ham had the highest carbon and land use footprints out of the meals we modelled, demonstrating the carbon and land intensity of pork meat. Pork pie, followed by roast turkey, were the next worse, trailed by the foods that do not contain meat. The vegan Christmas cake, for example, produced less carbon and used less land than the vegetarian fruit cake that contained eggs and butter, although in this case the relative differences were less striking.

Fruit cake climate change contribution by ingredients

Digging deeper, the pork meat made up 54 percent of the pork pie by weight, but contributed 81 percent of its greenhouse gas emissions.

Pork pie climate change contribution by ingredients

Meanwhile, the vegan vegetable-based pie, which had a third of the environmental impacts compared with the pork pie, generated more than three quarters of its impacts from the pastry crust, its contents of potatoes, mushrooms, and tofu being so environmentally benign by comparison.

Vegan pie climate change contribution by ingredients

Looking to the future, the global citizen will need to contribute no more than 2.9 tonnes of CO2-eq per year to meet the 1.5C Paris agreement threshold. This is equivalent to about 8kg a day, for all goods and services, not just food. In terms of servings from our Christmas dishes, one portion of the glazed roast ham already uses half that carbon budget. A combined meal of a serving each from the roast ham, the pork pie, and the fruit cake and eggnog would tally about 70 percent of an individual’s daily carbon budget, leaving only a small allocation for all other activities such as heating, transport, and presents. On the other hand, a person who ate a serving each of the vegetable pie, the squash Wellington, and the vegan cake would only use about 14 percent of their daily carbon budget, and a fairly small parcel of land.

There are many choices an individual can make to decrease their carbon or land footprint, but food makes a big part of these impacts. At Christmas when we tend to eat more and richer foods, it pays to keep in mind how much those choices take from the planet and to become aware of the favourable environmental profiles of plant-based alternatives. 

You can read more about how we model carbon footprints of food and cities in the papers here and here

– Additional research and reporting by Leopold Wambersie, PhD student at École de technologie supérieure.

Dr Thomas Elliot is a postdoctoral fellow at École de technologie supérieure in Canada.

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