Berners-Lee et al., 2012
https://faunalytics.org/wp-content/uploads/2015/05/GHG_Diets.pdf
Abstract
We calculate that the embodied GHG content of the current UK food supply is 7.4 kg CO 2e person1 day1 , or 2.7 t CO 2e person1 y1. This gives total food-related GHG emissions of 167 Mt CO2 e (1 Mt¼10 6 metric tonnes; CO 2 e being the mass of CO 2 that would have the same global warming potential, when measured over 100 years, as a given mixture of greenhouse gases) for the entire UK population in 2009. This is 27% of total direct GHG emissions in the UK, or 19% of total GHG emissions from the UK, including those embodied in goods produced abroad. We calculate that potential GHG savings of 22% and 26% can be made by changing from the current UK-average diet to a vegetarian or vegan diet, respectively. Taking the average GHG saving from six vegetarian or vegan dietary scenarios compared with the current UK-average diet gives a potential national GHG saving of 40 Mt CO 2e y1. This is equivalent to a 50% reduction in current exhaust pipe emissions from the entire UK passenger car fleet.
Keeping calories the same, they calculated the GHG of the average UK diet, then for 6 scenarios:
- Replacing all meat with dairy ("dairy heavy veggie")
- Adopting the average self reported diet of a US veggie ("actual veggie diet")
- Replacing meat with whole plant foods, keeping dairy the same as UK average ("thoughtful veggie")
- ditching all meat and dairy, and scaling up all foods equally to make up lost calories (i.e. not replacing animal products, just consuming more of everything else). This includes alcohol and sweets. ("undiscriminating vegan")
- Adopting the average self reported diet of a US vegan ("actual vegan diet")
- Replacing meat and dairy with whole plant foods ("thoughtful vegan")
Modelled 6 veggie/ vegan scenarios and found that all of them cost less compared to the average British diet, with savings on weekly food bill ranging from 5.0% to 14.6%. Largest savings were seen in diets that are arguably less realistic (one simply replaced all protein from meat with protein from dairy products for example). Following a hypothetical veggie diet resulted in significant food bill savings of 12.3%, and using real consumption data from US veggies (UK data was not available at the time) still resulted in an 8.8% decrease.
| Scenario type | Scenario | Cost at checkout (£ p/person/day | Cost saving vs staus quo | % cost saving |
|---|---|---|---|---|
| Baseline | Current average per capita UK food supply of 3458 kcal day−1 | £6.59 | £0.00 | 0.00% |
| Vegetarian | 2: US average vegetarian diet, normalised to UK food supply per capita energy | £6.01 | £0.58 | 9.65% |
| Vegetarian | 3: UK average diet with meat energy replaced by “healthy” non-dairy alternatives, normalised to UK food supply per capita energy | £5.78 | £0.81 | 14.01% |
| Vegan | 4: UK average diet with meat and dairy energy replaced by all plant-based alternatives, normalised to UK food supply per capita energy | £5.65 | £0.94 | 16.64% |
| Vegan | 5: US vegan diet, normalised to UK food supply per capita energy | £6.26 | £0.33 | 5.27% |
| Vegan | 6: UK average diet with meat and diary energy replaced by “healthy” plant-based alternatives, normalised to UK food supply per capita energy | £5.99 | £0.60 | 10.02% |
| Vegetarian | Average | £5.90 | £0.70 | 11.83% |
| Vegan | Average | £5.97 | £0.62 | 10.64% |
Diet data was from 2010 National Diet and Nutrition Survey (NDNS, 2010)
To calculate the GHG emissions embodied in each category we used estimates of greenhouse gas emissions up to the point of sale at a mid-sized supermarket chain in the northwest of England. The 61 foodstuff categories are those used by the retailer for operational management and accounting
purposes and are listed in Fig. 1. This chain has 26 stores and, although positioned in the market as one of the UK’s premium supermarket brands, we assume that the greenhouse gases embodied in its product range are representative of those sold by all other food retailers in the country.