Cows, cars and climate change
Last year’s summary of carbon dioxide levels in the atmosphere up to 2013 gives one pause for thought. There was a bigger increase in CO2 in the atmosphere from 2012-13 than had been recorded for nearly 30 years. Despite all we know, carbon is increasing faster than ever, and faster than imagined in IPCC’s ‘worst case’ scenarios. Last year CO2 in the atmosphere passed 400ppm for the first time for three months, this year it is likely to average over 400ppm for the whole year, perhaps for the first time in several million years.
In a meeting last year, I was discussing what interventions could conceivably make a significant reduction in our personal carbon budgets that wouldn’t need a radical (and thus scary) lifestyle change. Many of us know consumption of different foods produces different amounts of greenhouse gases (GHG), and I thought that changing consumption of meat could have a large impact. When I looked at the figures in detail, I was surprised by how large this impact could be.
A top-down view of global emissions
Agriculture, including forestry and other land uses (“AFOLU”) is a very major component of our emissions. According to IPCC, global greenhouse gas emissions are 49Gt CO2e (i.e. methane and other greenhouse gases converted to equivalent units of CO2). Of these 14% are for the transport sector (that’s 6.86Gt), and 24% are from AFOLU (so that’s 11.76Gt).
Looking at the transport sector’s emissions, in the US, 42% is due to domestic cars (EPA fastfacts data sheet: 787/1834mt), in the UK its 52% (64/123mt: DECC figures) and in the EU it’s about 41% (670/1650mt, EU data). Car ownership is higher in the EU and North America than many parts of the world, so it is likely that somewhere less than 50% of global transport will come from cars (i.e. <3.43Gt).
In contrast, livestock produce 7.1Gt of agriculture and forestry’s 11.76Gt. These figures are made up from methane from cow digestion (44%), land-use conversion to produce feed (27%) and 29% from cattle feed (grain, soya etc). Of this, about 4.6Gt CO2e is from cattle.
Thus, simply on a global basis, emissions from cattle probably exceed car emissions. This finding was reinforced by the Chatham House report (Livestock: Climate Change’s Forgotten Section) published in December.
Car for cow
Such a macro-analysis clearly has limitations. Because data for the US is widely available, and because I was quizzed by a US car journalist, I then looked at this from a “bottom-up”, household-level perspective.
USDA data, available online, shows that an average American’s per capita annual meat consumption is 59lb beef, 48lb pork, 70lb chickens. A recent paper suggests that the CO2-equivalent (CO2e) emissions per kg of meat are 32.15kg for beef, 3.91kg for poultry and 5.91kg for pork. (Another recent paper provides a similar estimate for beef at 31kg CO2e per kg meat.)
That suggests an average American’s meat consumption produces about 1.12 tonnes of carbon – the lion’s share of this is 862kg from beef.
Now let’s look at the data for domestic car use. According to US Federal Highway’s Agency, on average, each US car drives 12334 miles per year (19862km). A modern compact fuel efficient car is about 0.11kg CO2e per km. A two-car family would therefore, on average, emit about 4.37 tonnes of carbon from driving their 24668 miles. If that two-car family had four people in it (imagine parents and two teenagers), their meat emissions would be essentially the same at 4.44 tonnes.
Beef’s greenhouse gas footprint is very large (as Eshel’s paper highlights) because they are very inefficient at converting anything other than grass into meat. Increasingly, and especially in the US, demand for meat is leading to animals being fed concentrated food. On a global scale, enough calories to feed four billion humans are now being fed to livestock.
This concentrated diet turns beef cows into the resource-hungry SUVs of the livestock world.
But in many parts of the world, livestock production is nutritionally, economically, socially or environmentally important. In the UK, for example, much less concentrated food is used, so the GHG emissions per kilo of meat are typically lower than in the US but are still high compared with other foodstuffs. So, although in the UK cutting a family’s meat consumption may not have the same carbon savings as in the US, it would nonetheless be significant. It’s far too blunt a conclusion to suggest a vegetarian diet is the answer, but reducing our meat consumption may be a preferable option.
The larger point is that all our consumption (whether for food, water, cars or other goods) requires energy, and by changing patterns of consumption we can change emissions. For the US analysis, a family eating half the meat could make the same GHG saving as getting rid of a car, and this may have less of an impact on lifestyle and therefore be easier to achieve.
The person from the US car industry ended up shouting at me down the phone: “My industry has been under enormous pressure to reduce GHG emissions, and every driver knows about the need for efficiency. Why isn’t the same pressure being put on me to change my diet?” Quite.
This is an edited version of Tim Benton’s blog that first appeared on the Global Food Security website.
About Tim Benton
Tim Benton is GFS Champion and an interdisciplinary researcher working on issues around agriculture-environment interactions. Formerly, he was Research Dean in the Faculty of Biological Sciences, University of Leeds, and Chair of the Africa College Partnership, an interdisciplinary virtual research institute concerned with sustainable agriculture in sub-Saharan Africa. He has worked on the links between farming and biodiversity (and ecosystem services) for many years.