Why Eating Local Makes a Difference in Your Carbon Footprint

In January 2020, I wrote a post titled "One Less Thing to Worry About in Your Carbon Footprint: Whether Your Food Is Local" based on one of our favorite sources: Our World in Data. The online research site says "the goal of our work is to make the knowledge on the big problems accessible and understandable."

At the time, Our World in Data's senior researcher Hannah Ritchie wrote about reducing the carbon footprint of your food:

"‘Eating local’ is a recommendation you hear often – even from prominent sources, including the United Nations. While it might make sense intuitively – after all, transport does lead to emissions – it is one of the most misguided pieces of advice.... GHG emissions from transportation make up a very small amount of the emissions from food and what you eat is far more important than where your food traveled from."

Ritchie concluded that what you eat is far more important than where it came from, because of the huge carbon footprint in some foods like red meat compared to others. "Whether you buy it from the farmer next door or from far away, it is not the location that makes the carbon footprint of your dinner large, but the fact that it is beef," wrote Ritchie.

This is, of course, absolutely true, as can be seen by the graph, where the beef bar at top overwhelms every other food and the red bar representing transport is almost invisible.

But over the course of 2020, when I was writing a book on living a 1.5-degree lifestyle, I kept revisiting this question of local food and it troubled me. As I noted in the earlier post, "Our household rule is that if it grows here (in Ontario, Canada) then we wait until we can eat the local version, but I still get to have a grapefruit for breakfast and some guacamole at lunch." But did this research mean that California strawberries and lettuce were back on the menu?

Our World in Data often bases its work on earlier published research, reinterpreting it and reformatting it for the modern age, noting on its about page that "a key part of our mission is therefore to build an infrastructure that makes research and data openly available and useful for all." Much of this post was based on the work of Joseph Poore and Thomas Nemecek and their 2018 study on the global impacts of food production, which mentioned transport emissions, but I couldn't find where they clearly identified them.

Ritchie also mentions Christopher Weber and Scott Matthews's 2008 study "Food-Miles and the Relative Climate Impacts of Food Choices in the United States." This study comes to the same conclusion as Ritchie:

"Transportation as a whole represents only 11% of life-cycle GHG emissions, and final delivery from producer to retail contributes only 4%. Different food groups exhibit a large range in GHG-intensity; on average, red meat is around 150% more GHG-intensive than chicken or fish. Thus, we suggest that dietary shift can be a more effective means of lowering an average household’s food-related climate footprint than 'buying local.' Shifting less than one day per week’s worth of calories from red meat and dairy products to chicken, fish, eggs, or a vegetable-based diet achieves more GHG reduction than buying all locally sourced food."

Again, no argument here, but this was written back in 2008 when everyone was talking about local food, when living the 100-mile diet was the talk of the town, and people were discussing this as a one-or-the-other thing. The authors are trying to demonstrate again that what you eat matters a lot more than where it came from.

But much depends on the food. Although table C demonstrates that red meat has the biggest climate impact on an average household and that delivery and freight are thin little bars on the left, note that fruit and vegetables have a pretty big impact. Take out red meat and dairy and they become dominant.

Continue to table B and out the total contribution of transportation, fruit and vegetables actually contribute more than meat, and it is almost entirely by truck. The study states: "Final delivery (direct t-km) as a proportion of total transportation requirements varied from a low of 9% for red meat to a high of around 50% for fruits/vegetables." (If you are wondering why gas pipelines are on the chart, it's for the contribution to fertilizer production.)

So when you are eating fruits and vegetables, you are eating a lot more diesel, but according to the authors, it is still a small proportion of the total footprint of the food that we eat. Or is it?

The Impact of the Cold Chain

When you get to the "Discussion and the Uncertainties" in the results, the authors note: "Refrigerated trucking and ocean shipping of fresh foods are more energy-intensive than the average intensity of trucking or ocean shipping. However, neither of these uncertainties are likely to change the overall results of the paper substantially."

One might argue that it changes the results significantly. While studying the issue for my sustainable design class at Ryerson University, my student Yu Xin Shi found refrigeration accounts for 20% of the fuel used in transportation and that 3% to 7% of the global leakage of HFC refrigerants (a major greenhouse gas) came from the transportation of food. She found that a single head of lettuce spent 55 hours on a refrigerated truck. Her source was was work by Professor Jean-Paul Rodrigue of Hofstra University.

I asked Rodrigue for a comment and the professor tells Treehugger:

"You are asking for technical details that I cannot provide as an indirect source of information since I have not made these calculations. This said, the ocean shipping of refrigerated goods is substantial... It may be a safe assessment that the footprint of cold chain logistics may be underestimated, but by how is at this point quite an ordeal."

So I cannot conclusively say how much diesel is in my salad from California, but do believe that it is higher than what ends up in the Our World in Data chart. As such, I think it is not correct to say that eating locally doesn't matter — and, depending on what you eat, it can matter a lot. From a carbon footprint point of view:

1. Cutting back on red meat and dairy has the most immediate and dramatic impact. Whether they are local or not is almost irrelevant.
2. For fruit and vegetables, eat seasonal first; hothouse tomatoes can have a higher footprint than chicken.
3. But also for fruit and vegetables, the transportation footprint is significant, as much as 50%. They are such low carbon foods that it isn't huge, but there are still alternatives and it is still better to eat local and seasonal than to truck strawberries and lettuce from California.

We are not talking about much when we are living a typical North American lifestyle that emits 18 tonnes of carbon per year, but when you get down to counting grams trying to maintain a 1.5-degree lifestyle and emit less than 2,500 kilograms per year, it can add up. I don't think we should ever say that food miles don't matter, because they add up too. I can't put a hard number on it, but local food still matters.