Food: the free lunch of climate change

29 November 2019

Changes to diet and food sourcing are the closest thing to a free lunch in the battle against climate change

Reduce red meat, waste less, and shop seasonally to cut your food-print in half and save up to 1.5 Tonnes CO2e per year. Cheaper, healthier, lower carbon.

Agriculture’s contribution to our carbon footprint

One of the best descriptions I’ve found of the impact of food on our carbon footprint is in There is No Planet B, by Mike Berners-Lee, which, along with his earlier book ‘How Bad are Bananas’, is required reading for anyone serious about reducing their personal carbon footprint.

Mike estimates the total carbon footprint of agriculture at nearly one quarter of the global total of humanity’s emissions (23% to be precise), split approximately as follows:

*Source: There Is No Planet B, Mike Berners-Lee, my categorisation*

The immense impact of rearing animals for food can immediately be seen from this categorisation. Direct methane emissions from the effluxions of cows and sheep plus the impact of deforestation for raising animals (mainly beef herd) makes up one-third of the global food footprint. This is before the carbon cost of growing feed for these animals and heating barns for overwintering and so on. The combined impact of eating meat probably accounts for half the carbon footprint of our species.

We need to eat less red meat and more vegan or vegetarian

Mike’s analysis also shows a clear hierarchy of impacts, which can broadly be put into the following categories, ordered by greenhouse gas emissions per 50g of protein:

Of course we don’t eat just beef or just nuts. We need to look at the impact of different typical diet mixes. The potential impact of all of these changes on the carbon footprint of a typical diet has been analysed by www.shrinkthatfootprint.com and can be found here. They estimate the total annual carbon footprint of different types of diet as follows:

These figures are based on typical US diet, but I’ve seen similar impacts from different studies for UK diets also. Some important conclusions can be drawn from this analysis in terms of the priority order of dietary actions to combat climate change:

Eat less beef. The overall carbon cost of beef herd as a protein source is an astonishing 25x the impact of direct sources such as nuts, pulses etc. Cutting out or minimising beef burgers, steaks, etc is clearly the first step, particularly given the knock-on impact of growing beef consumption on deforestation. Beef should be seen as an occasional treat.
Eat less red meat. Lamb is better than beef, in significant part because it does not drive deforestation. But it is still 10x the impact of vegan protein sources. For this purpose, farmed crustaceans (mainly prawns in the western diet) are similarly problematic.
A diet without red meat captures around half the typical potential carbon savings. Substituting pork and chicken, and farmed fish, in place of red meat, will result in major carbon savings. Eggs and diary are lower still at around 2kg CO2e per 50 g of protein.
Vegan and vegetarian are best. The vegan diet is the most efficient as it requires no feeding of animals in the supply chain (which results in major energy leakage). A vegan diet cuts the average carbon food-print by one-third. However, people moving to a diet that is more vegan, more vegetarian, and which largely cuts out red meat will capture most of the available dietary gains and significantly cut their food-print.

We need to waste less

Estimates of how much food we waste in Europe range from 5% to 25%. A central estimate from the Food and Agriculture Organisation of the United Nations is around 10%. Cutting out our own personal food waste is an easy win through adopting just a few simple habits:

Only cooking and serving the amount we will eat.
Saving and reusing left-overs, regularly checking our fridge for items to be used up.
Storing left-overs in air-tight containers to maximise useable life.
Treating ‘best before’ dates with the healthy scepticism they deserve.

In restaurants, think about asking for a small portion if you aren’t hungry or signal your dislike of food waste by asking them to pack up leftovers for you to take away.

Many councils now run composting services for food waste, to prevent it going to landfill. This may have the unintended consequence of making food waste seem less bad. Any food waste should definitely be composted rather than put in the bin, because in landfill it will rot in a way that produces the very damaging greenhouse gas, methane. By contrast, methane emissions will be lower in a good composting facility. However, composting should not be viewed as a free pass. First, energy has been wasted in producing the food, and this has a carbon consequence. Second, the composting process itself results in greenhouse gas emissions.

We need to shop seasonally

We are now used to being able to buy everything all the year round. This has resulted in vast and complex food supply chains involving food travelling vast distances to arrive at our plate and in the development of artificial hothouse environments to produce summer fruit and vegetable off-season. There has been a lot of focus recently on reducing air miles and shopping locally. But producing food out of season is actually much worse. In his book How bad are bananas? Mike Berners-Lee identifies that 1kg of Tomatoes can have a carbon footprint of anything from 0.4kg to 50kg:

0.4kg if organic loose tomatoes of a traditional variety grown locally in July
9.1kg overall average
50 kg if cherry tomatoes grown in a hothouse in March

Astonishingly, per kg of weight, hot-housed cherry tomatoes have twice the footprint of beef steak! As a result, shopping seasonally is probably even more important than shopping locally. Although we hear that local sourcing is best, this is only right for food that is in season. Out of season food, grown using artificial heating, is almost certainly worse than getting it from the nearest warm climate where it is in season (e.g. Spain or North Africa).

The benefits of shopping seasonally enable us to access food from around the world, provided it is shipped not flown. Foods like bananas, sweet potatoes, apples, oranges are typically shipped, because they travel well. Shipping adds little to their carbon footprint. By contrast avocados are typically air freighted and so environmentally much more damaging.

To assess the carbon impact of our food we e can look at the country of origin and ask ourselves two questions:

Could it have been grown naturally in the country at this time of year without need for artificial heating?
If it’s from overseas, will it have been shipped or flown here? Packaging provides a clue: heavily packaged food will almost certainly have been air-freighted.

Mike Berners-Lee estimates that eating seasonally and avoiding hot-housed and air-freighted food might easily save 10% on the carbon footprint of the typical UK diet. In How bad are bananas? Mike provides a helpful list of foods that are seasonal by month in the UK as well as foods that can generally be eaten year-round by virtue of being shipped rather than flown in from overseas.

Healthier, cheaper, and more sustainable

Pulling this all together, the average UK citizen should be able to roughly half the carbon footprint of their diet by making simple changes in three areas:

These simple steps can result in a significant carbon saving without a major reduction in quality of life. We don’t need to jump to extremes. Most of the benefits are gleaned from significant shifts in the proportions of what we eat rather than outright bans. Overall, we should be able to halve our footprint from food, saving 1 to 1.5 Tonnes CO2e per annum.

Reducing carbon footprint of our food consumption is one of the few areas where there are few troubling second order or rebound effects. Eating in a more sustainable way is also likely to be cheaper and healthier. So there really is such a thing as a free lunch.

This blog if part of a series sharing our learning and experiences as we adopt a Middle Class Approach to Decarbonisation