Diets and Methane Emissions

Eimear Leahy

Seán Lyons

Richard S.J. Tol

Motivation

• Agriculture is responsible for 30% of the world's GHGs (CO2, N2O, CH4)

“producing 0.25kg of mince releases as much greenhouse gases to the air as driving an average car for 14km”

“going vegan is 50% more effective than switching to a hybrid car in reducing greenhouse gas emissions”

“if every American skipped one meal of chicken per week and substituted vegetarian foods instead, the carbon dioxide savings would be the same as

taking more than a half-million cars off U.S. roads”

Motivation ctd• Meat Production alone = 18% of all GHGs (UNFAO, 2006)• Livestock accounted for 92% of all methane emissions from

agriculture in the USA in 2003 (bacteria from ruminants)– Methane makes the second largest contribution to anthropogenic

climate change after carbon dioxide– Meat production set to double by mid century– UK average consumption is 50g per day, which is more than the

recommended amount

“In Ireland reducing methane emissions produced by farmed animals by 20% is the equivalent of taking 25% of Ireland's cars off the road for a year”

• No point in reducing production in one country and replacing consumption with imports

Literature• No study of vegetarianism using household data

• A few minor studies/polls carried out by vegetarian organisations -usually very small, unrepresentative samples

• Meat expenditure patterns and determinants of meat consumption have been studied in several countries using household expenditure data

– Ireland by Newman et al (2001)– USA by Nayga (1995)– UK by Burton et al (1994)– Japan by Chern et al (2002) – Mexico by Gould et al (2002)

• This is the first paper to estimate the number of vegetarian households in multiple countries

Data and Methodology

• Living Standard Measurement Studies– Albania, Azerbaijan, Bosnia, Bulgaria, Kosovo, Serbia,

Kyrgyzstan, Tajikistan, Brazil, Peru, Guatemala, India, South Africa, Tanzania, Ivory Coast, East Timor, China

• Household Income and Expenditure Data– Ireland, France, Nepal, Jamaica, USA, UK, Vietnam, Russia,

Singapore, Australia, and Germany

• 120 observations (country-year) in total, from some 600,000 micro-data

• Consumption versus Expenditure• Problems with recall and infrequency of purchase

Infrequency of purchase

• Only include households that have done a “full shop”

foodsharei =(foodexpi/nid)/(Incomei

t)

• Find mean and standard deviation of foodshare for each income decile

• Omit from analysis if

foodsharei <[avgsharej - (0.5*sdsharej)]

USA

• The US Consumer Expenditure Survey reports expenditures for 1 or 2 weeks

• Divides food purchases into 9 categories– cereal and bakery products, meat products, fish products, eggs, milk

and dairy products, processed fruit or vegetables, fresh fruit or vegetables, sweets, non alcoholic beverages and miscellaneous food and oils

• Omitted from analyses if expenditure in 6/9 groups = 0• Remaining sample: >5,000 households per year• Find % of households that report zero

expenditure/consumption on meat products• “At home” consumption only

Results: Per Capita Income

0%

10%

20%

30%

40%

50%

60%

0 5000 10000 15000 20000 25000 30000 35000

Per Capita Income PPP

% V

eg h

ou

seh

old

s

Results: Per Capita Income

0%

10%

20%

30%

40%

50%

60%

0 5000 10000 15000 20000 25000 30000 35000

Per Capita Income PPP

% V

eg h

ou

seh

old

s

Latin America, Central Europe, Vietnam, Nepal

East Timor, Ivory Coast, India, Eastern Europe

Results: Per Capita Income

0%

10%

20%

30%

40%

50%

60%

0 5000 10000 15000 20000 25000 30000 35000

Per Capita Income PPP

% V

eg h

ou

seh

old

s

Russian Federation

China, Africa

Results: Per Capita Income

0%

10%

20%

30%

40%

50%

60%

0 5000 10000 15000 20000 25000 30000 35000

Per Capita Income PPP

% V

eg h

ou

seh

old

s

Australia

USA

Per Capita Income: World

0%

10%

20%

30%

40%

50%

60%

0 10000 20000 30000 40000 50000 60000

PPP Per Capita Income

% V

eg

ho

us

eh

old

s

Meat Production

0%

10%

20%

30%

40%

50%

60%

0 50 100 150 200 250 300

Per Capita Meat Production

% V

eg h

ou

seh

old

s

IrelandUSA, France, Brazil, UK

East Timor

Meat Production

0%

10%

20%

30%

40%

50%

60%

0 50 100 150 200 250 300

Per Capita Meat Production

% V

eg h

ou

seh

old

s

Central Europe, Latin America, Asia

India, Peru, Eastern Europe

Results: Religion

0%

20%

40%

60%

80%

100%

Guatem

ala Peru

Tajikis

tan

Franc

e

Ivory

coas

t

German

yBra

zil

Alban

ia

Irelan

d

ChinaSer

bia

Russia

Vietna

m

Jam

aica

Tanza

nia UK

Bulgaria

South A

frica

Bosnia

USA

Timor L

este

Kyrgyz

stan

Azerb

aijan

India

Nepal

% Veg Households % Hindu

Extensions

• Results above are for all-vegetarian households• There are mixed households as well• Methodology

– Observe expenditure for one person households– Predict meat and non-meat expenditure for each

household given its income– Derive probabilities of the share of meat in total food

expenditure, conditional on the hypothesized number of vegetarians

– Compare probability to observed meat-share

Vegetarians in Mixed households

0%

2%

4%

6%

8%

10%

12%

14%

0% 3% 6% 9% 12% 15% 18% 21% 24% 27% 30%

share of meat in total expenditure

prob

abilit

y

Two person household

Share of meat expenditure if

one of the two is a vegetarian

Share of meat expenditure if

neither of the two is a vegetarian

Conclusions

• There are over 900 million vegetarians• 94% of these are vegetarians of necessity• The remaining 6% are vegetarians of choice• In the medium term, the number of vegetarians will fall

and methane emissions rise• In the long term (and in the medium term in the OECD),

rising vegetarianism will curb the growth in methane emissions

Per Capita Income: World

0%

10%

20%

30%

40%

50%

60%

0 10000 20000 30000 40000 50000 60000

PPP Per Capita Income

% V

eg

ho

us

eh

old

s