Total greenhouse gases
The total from food is taken to be 2.2 tonnes CO2 equivalent per person
The components are:
|Component||UK million tonnes||Tonnes per person||Avoidable tonnes per person|
|meat and dairy consumption||24||0.4||0.4|
|Processing of food||11||0.18||0.15|
|Decomposition of food||13||0.22||0.2|
Other estimates are:
|Per person per year||Source||Notes|
|0.6 tonnes CO2||||for food and drink|
|1.4 tonnes CO2||||'Food and catering'|
|1.9 tonnes CO2 equ.||||(The Cabinet Office report) from a UK total of 116 Mt CO2 equivalent for food - 110 Mt plus an allowance of 6 Mt for the balance of imports over exports (21 less 15 Mt)|
|2.0 tonnes CO2 equ.|||
|2.1 tonnes CO2 equ.||[CG, 10]||the main difference from source  is in the inclusion of methane and nitrous oxide as an equivalent amount of CO2.|
• Use of fertilizers generates nitrous oxide on breakdown in the soil. This is 27 Mt CO2 equivalent .
• Manufacture and transport of fertilizers generates 9 Mt CO2 .
• This total of 36 Mt CO2 equivalent for UK fertilizer use is equal to 0.6 tonnes CO2 equ. per person. It should be scaled up to allow for UK food production being less than Uk consumption. Overall UK production is only 60% of UK consumption , but for meat, the figure is 80-90%. Since meat production is much more energy intensive than fruit and vegetables, the scaling up will assume a figure of 85% giving an estimate 0.7 tonnes CO2 equ. per person).
So switching to organic food can reduce an individual's carbon footprint by 0.7 tonnes CO2 equ.
Meat and dairy foods
• Production of meat and dairy products generates methane from animals and slurry, which amounts to 19 Mt CO2 equivalent .
• CO2 from meat and dairy farm operations amounts to 3 Mt CO2 .
• This total of 22 Mt CO2 equiv from meat and dairy production should be scaled up to allow for UK meat and dairy production being equal to around 90% of UK consumption , giving an estimate of 24 Mt CO2 equivalent (0.4 tonnes per person).
So switching to a vegan diet can reduce an individual's carbon footprint by 0.4 tonnes equ.
• UK road transport of food generates 7 Mt CO2  + 
• Road transport outside UK & sea transport generates 7 Mt CO2  +  (2/3 and 1/3 respectively)
• Air freight generates 3 Mt CO2 
• The total of 17 Mt CO2 is equivalent to 0.3 tonnes per person.
So switching to buying local food could save most of this total e.g. 0.25 tonnes per person.
• The manufacture of food packaging generates 10 Mt CO2 
• The methane and CO2 from decomposition of biodegradeable packaging in landfill sites is 4Mt CO2 equ. 
• The total of 14 Mt CO2 is equivalent to 0.23 tonnes per person.
Buying minimally packaged foods could save most of this total i.e. 0.2 tonnes per person.
[Composting organic packaging could save a proportion of it]
• The processing of food generates 11Mt CO2  (0.18 tonnes per person).
Avoiding processed food could save most of this i.e. 0.15 tonnes per person
In the UK, about one third of the food bought is thrown away, and at least half of this is food that could have been eaten . Inedible food includes potato peelings, bones, banana skins and teabags. Edible food can be discarded because too much is prepared, or because it has gone past its use-by date and so on.
Another way of looking at this is that relative to food eaten, on average another 25% is wasted, and a similar amount is inedible food.
If this 25% waste is reduced by half to 12.5%, then the edible food bought falls from 125% of what is eaten to 112.5%, and all emissions connected with food fall by one tenth - and the total amount discarded (edible plus inedible) falls by one quarter.
If someone throws away more food than average by half as much again, then the edible food bought rises from 125% of what is eaten to 137.5%, and all emissions connected with food rise by one tenth - and the total amount discarded (edible plus inedible) increases by one quarter.
Landfill decomposition of food
• The rotting of unused food in landfill sites releases gases (methane + CO2) that total 13 Mt CO2 equ  (0.22 tonnes per person)
Composting or re-using food residues could save most of this i.e. 0.2 tonnes per person. This amount would be more or less depending on how much edible food is wasted.
Greenhouse gases that are not avoidable
These comprise 
• methane from tilling and soil management (4 Mt CO2 equ.)
• CO2 from arable farm operations (3 Mt CO2)
• operation of retail stores (4 Mt CO2)
These total 11 Mt CO2 equ (0.2 tonnes per person)
• UK food production is only 60% of UK consumption 
• Food exports from the UK are worth around £6.5bn - with cereals and fish making the largest contribution .
• Food imports are worth almost £20bn, vegetables and fruit being the largest category .
• The origin of UK food is (2006, based on unprocessed farm-gate prices) :
29% Europe (EFTA)
5% N. America
4% S. America
Units & Abbreviations
Mt: million tonnes (referring to the UK total)
CO2 equ. : CO2 equivalent
Figures given are per year
See Reference List