Very little of global food is transported by air; this greatly reduces the climate benefits of eating local

People often think that eating ‘local’ – buying foods which are produced close to home – is one of the most effective ways to reduce our carbon footprint.

This is certainly true for foods that are transported by plane. But the reality is that very little of our food is.

Most food travels by sea, not by air

One simple way to compare the means of transport for food is summing up how many kilometers planes with food freight travel; and compare this to how many kilometers trains, ships, and trucks travel.

But this does not give the complete picture because a boat can carry much more food for a given distance than a truck can. To give an informative comparison, we use a metric called ‘food miles’; this is calculated as the distance each transport method covers multiplied by the quantity of food transported (by mass). This gives us a comparison of food miles in tonne-kilometers.

The chart here shows the share of global ‘food miles’ by transport method. This data is sourced from the work of Joseph Poore and Thomas Nemecek, published in the journal Science in 2018.[1]

As the data here shows, only 0.16% of food miles come from air travel. Most – nearly 60% – comes by boat.

You can see this data in absolute terms, in tonne-kilometers, in our chart on global food miles by transport method.

Whether food travels by sea or air makes all the difference

Transporting food by air emits around 50 times as much greenhouse gases as transporting the same amount by sea. More specifically, 0.023 kilograms of carbon dioxide-equivalents (CO2eq) per tonne-kilometer by sea, versus 1.13 kilograms CO2eq by air. We see these emission factors for different transport modes in the table.

For food that is transported by sea, transportation doesn’t actually add much to the carbon footprint. Since most of our food is transported by sea, transport emissions only account for 6% of the carbon footprint of food, on average.[3]

But for those food items that travel by air, travel distance does have a large impact. We should avoid air-freighted goods where we can.

Which foods are air-freighted? How do we know which products to avoid?

Foods which are air-freighted tend to be those which are highly perishable. This means they need to be eaten soon after they’ve been harvested. In this case, transport by boat is too slow, leaving air travel as the only feasible option.

Some fruit and vegetables tend to fall into this category. Asparagus, green beans, and berries are common examples of air-freighted goods.

It is often hard for consumers to identify foods that have traveled by air since they’re rarely labeled as such. This makes them hard to avoid. A general rule is to avoid foods that have a very short shelf-life and have traveled a long way (many labels have the country of ‘origin’ which helps with this). This is especially true for foods where there is a strong emphasis on ‘freshness’: for these products, transport speed is a priority.

Emission factors for freight by transport mode (kilograms of CO2eq per tonne-kilometer)[2]

Example: how does the footprint of vegetables change if they travel across the world by plane vs. boat?

Let’s take the example of asparagus.

If you live in the UK, you may have noticed on food labels that asparagus is often imported from Peru. They often come by plane. How does this affect their carbon footprint?

The average carbon footprint of asparagus is around 0.4 kilograms CO2eq per kilogram. Flying from Lima to London is around 10,000 kilometers. If we were to fly one kilogram of asparagus over this distance, this would emit around 11 kilograms of CO2eq [10,000km * 1.13 kilograms CO2eq per tonne-kilometer for flying / 1000 = 11.3 kg CO2eq per kg]. Suddenly the footprint of your asparagus changes from being a low-carbon food to a relatively high-carbon one, at almost 12 kg CO2eq per kg. It has a higher carbon footprint that a kilogram of chicken or pork.

It is the fact that it’s flown, rather than the travel distance itself that gives asparagus a large footprint in this example. If it traveled the same distance by boat, the travel emissions would be only 0.26 kg CO2eq per kg [10,000km * 0.026 kilograms CO2eq per tonne-kilometer for transport by boat / 1000 = 0.26 kg CO2eq per kg]. So its total footprint would be around 0.67 kg CO2eq per kg, which still makes it a low-carbon food option.

Endnotes

1] Poore, J., & Nemecek, T. (2018). [Reducing food’s environmental impacts through producers and consumers. Science, 360(6392), 987-992.

2] These emissions factors by transport mode are those applied in the analysis by Joseph Poore and Thomas Nemecek (2018), published in Science. These emission factors are sourced from [Ecoinvent v3.3, a comprehensive database that is commonly used in international life-cycle analyses (LCA). Emission factors can span a range of values depending on factors such as the efficiency of the vehicle used; packing/loading density of freight; and distribution between passenger and freight allocation in shared transport; amongst other factors.

[3] You might think that this figure of 6% is strongly dependent on where in the world you live – that if you live somewhere very remote, that the role of transport must be much higher. But this is not really the case. Let’s take the example of beef from a beef herd. The average footprint of this beef is approximately 60 kilograms of CO2eq per kilogram of beef. Let’s compare the transport footprint of buying from your local farmer (who lives just down the road from you), versus someone in the UK transporting beef from Central America (approximately 9000 kilometers away). Transporting food by boat emits 0.023 kilograms of CO2eq per tonne of product per kilometer. To transport the 9000 kilometers from Central America to the UK therefore emits 0.207 kilograms CO2eq [9000km * 0.023kg per tonne-kilometer / 1000 = 0.207 kg CO2eq per kg]. This is only equivalent to 0.35% of the total footprint of the 60 kilograms of CO2eq per kilogram of beef. If you buy from your local farmer – let’s assume you walk there, and have zero transport emissions – your beef footprint is 59.8 kilograms CO2eq per kilogram [we calculate this as 60kg - 0.2kg]. It makes almost no difference. Especially for foods with a large footprint, transport as a share of the food’s total emissions is fairly insensitive to the distance traveled.

Where this page came from

This page was imported from Our World in Data. “Very little of global food is transported by air; this greatly reduces the climate benefits of eating local” by Hannah Ritchie (January 28, 2020), published by Our World in Data under CC BY 4.0. Changed here: set as a page, its interactive charts shown as pictures. Data from third parties keeps its own licence.

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