8/8/2019 Environmental Impact of Vegans Versus Conventional Diets in the UK

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Environmental

impactof vegan versus conventional diets in the UKStephen WalshI

t has long been recognised that

vegans need less land, water andenergy to meet their dietaryneeds. It is also increasinglyrecognised that vegan diets causeless global warming impact.However, quantifying how muchless is not straightforward as itrequires a lot of information onthe impact of different foods.

In 2006, a 400,000 study sponsoredby DEFRA reported on theenvironmental impact of agriculturaland horticultural commodities

produced in the UK1. The results havesince been slightly updated and thelatest spreadsheets (last updated in2007) are available from the authors.The analysis that follows is based onthese updated figures.

This DEFRA study provides a solidreference point for examining theenvironmental impact of differentdiets in the UK. The strengths of thestudy include: the breadth ofproducts considered using a consistentapproach; the focus on the UK; andthe wide range of environmentalimpacts considered.

The DEFRA study calculated theimpacts associated with a givenquantity of selected products at thefarm gate. DEFRA also publish figuresfor the annual supply of the sameproducts (including imports) goingback to 1985.2 I combined these twosources of information with figures forUK population to get an estimate ofthe total greenhouse gas impact of

livestock consumption per person inthe UK from 1985 to 2007, measuredin kilograms of carbon dioxideequivalents per year (on a 100 yearhorizon).

The modest dip in the early 1990s wasdue to a drop in consumption of beef.

To get to a realistic comparison of theimpact of various diets, we need toexpress the consumption of each foodin terms of calories as when substitutingone food for another we should keepthe total number of calories the same.

There is good data available from theUnited Nations Food and AgricultureOrganization (FAO) on the mix offoods available in the UK up to 20033.The FAO data is for supplied caloriesrather than consumed calories whichare much lower due to food wastage.Total food calories per person per dayin the UK for 2003 were 3450 kCal.

The DEFRA reports1,2 consider eachmajor type of meat (pig, cow, sheepand chicken) separately, allowing the

impact of variations in the type ofmeat consumed to be considered.I matched the percentage of caloriesfrom each animal food to the FAOsupply figures as closely as possible.

Some adjustment was needed toattribute calories reported as non-dairyanimal fats to specific meat products.

The main plant foods for humanconsumption considered in theWilliams et al report1 were potatoes,bread wheat and British grown tomatoes(a very untypical high-impact plant food

due to the use of heated greenhouses).Fortunately, soya and rapeseed wereincluded as animal feeds as part oftheir analysis of animal products.

As rapeseed is produced mainly as anoil crop, all the impact of the rapeseedis attributed to the oil in my analysis.Overall plant food consumption wasrepresented by a mix of soya, rapeseed,wheat and potatoes rather thanfollowing the more detailed breakdownin the FAO statistics. Wheat usedirectly matched the FAO figures;

rapeseed oil matched total vegetableoil and nut use; 10% of calories in thevegan diet were attributed to soya; andthe balance of calories was attributedto potatoes.

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This simplification of the plant part ofthe diet is unlikely to have distorted the

results as there is relatively little variationin the impacts of different field-grownunprocessed plant foods per calorie:sugar appears to have a lower impactthan potatoes while fruit and vegetableshave a higher impact.

Conventionally grown foods are used inthe analysis that follows as these aremuch more common than organicallygrown foods. The main difference fororganic food in the DEFRA report is ahigher arable land requirement due to

lower crop yields.

The fraction of calories contributed byeach food to each of the diets that Ianalysed is shown in the table above.

The key results are shown inthe table right. Impacts aremeasured in terms of landand water requirementsand in terms of the globalwarming effect measured inkg of CO2 equivalents. It

should be noted that the

figures in the second tableare based on theproduction of food and donot include food transport,abattoirs, bakeries,packaging, shops orrefrigeration and cooking athome. Production andtransport of animal feeds isincluded.

Greenhouse gas impacts are usuallycalculated in terms of CO2 equivalents

over a 100 year horizon but if we aremore concerned with the immediatefuture then a 20 year horizon is moreappropriate.

Replacing cow and sheep meat withpoultry and pig meat leads to significantreductions in land requirements and ingreenhouse gas impacts. Replacing allmeats with dairy products also leads toa significant decrease, though dairy haslimited advantage over poultry and pigmeat and indeed is worse in terms of

short-term global warming effect.A more typical lacto-vegetarian diet withabout 15% of calories from dairy productsshows more advantage over a conventionalUK diet, while a vegan diet has thelowest environmental demands of all.

Food

1 Williams A.G. et al. Determining the environmental burdens and resource use in the production of agricultural and horticultural commodities. Main Report. Defra ResearchProject IS0205. Bedford: Cranfield University and Defra; 2006. http://randd.defra.gov.uk/Document.aspx?Document=IS0205_3959_FRP.doc (accessed 28 September 2009).

2 Agriculture in the UK 2008 Tables and Charts: Tables 5.13-5.17 and table 5.19) https://statistics.defra.gov.uk/esg/publicat ions/auk/2008/excel.asp (accessed 28 September 2009)

3 FAOSTAT Food Balance Sheets (UK, 2003 selected) http://faostat.fao.org/site/368/DesktopDefault.aspx?PageID=368 (accessed 28 September 2009)

Note: Stephen's figures have already been used by The Times on 27 October.

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The figures may slightlyunderestimate the benefits of avegan diet as the DEFRA data2 may

miss some imported processed meatsand the Williams et al report1 doesnot quantify the impact of fish,

which provides about 1% of UKcalories. Also the impact of animal

use on deforestation and other landuse change was not considered.Meat processing and storage may bemore energy intensive than plant

food processing and storage. On theother hand, a less basic vegan dietincluding foods grown in heated

greenhouses or transported by airwould offer much less benefit interms of global warming, though it

should still have advantages in termsof land use.

Based on the DEFRA report1, a vegan

diet based entirely on organic foodswould have little or no advantagein land use over a conventional UKdiet but would in other respects havesimilar advantages to a conventionallygrown vegan diet. Some otherreports give more favourable resultsfor organic farming and vegan-organic methods may give differentresults to conventional organicmethods.

Overall, producing a basic vegan diethas about a third of the resourcedemands and global warming impactof a conventional diet a substantialadvantage, particularly in terms ofland requirements as human foodproduction dominates land use.