Should I Stop Eating Meat? Part III
Creating ‘example diets’ and comparing their CO2e numbers to other activities
Part of a series. Part II here.
Context is everything
What’s the point in comparing these numbers within the context of diets if we have no way of comparing these numbers with all the other aspects of our lives? Who really cares if chowing down on meat breakfast, lunch and dinner for a year is ‘worse’ for the environment if our choice to drive rather than bus our daily commute dwarfs that?
Now it’s time to try and build these comparisons. To do this we’ll make heavy use of the work of Mike Berners-Lee (MBL) and his amazing book How Bad Are Bananas? (HBAB). We’ll:
- use PN2018’s numbers to build some annual CO2e numbers for ‘representative diets’
- use MBL’s numbers to come up with some generic comparisons
- for the sake of some (much needed) introspection, use my last year to come up with a few specific numbers for me
It is worth pointing out that we need to be comparing like-for-like. The numbers from PN2018 are from an LCA and so we should only compare these numbers to other numbers that have been computed along the same lines i.e. capturing both direct and indirect emissions to prevent comparing ‘footprints’ to ‘toe prints’. This was the mistake originally made in the 2006 FAO paper when the comparison was made between livestock vs transport. Only the emissions from exhausts were considered for transport, rather than the embodied CO2e that exists in manufacturing cars, building roads from cement etc. Small point, but important to note to prevent skewing comparisons. Lucky MBL has done all the work for us.
Example Diets
So that we can make some simple comparisons, and under our previous assumptions about meat only featuring in a diet for protein content, let’s make a few more (fairly realistic) assumptions:
- based on standard portion sizes from perusing the supermarket and USDA guidance when we talk about ‘a meal’ it’ll be referring to 50g worth of protein as a standardised measure
- let’s assume that ‘beef’ is just a straight average of beef and dairy herd beef
- meals outside of those that we focus on are all the same — everyone still eats their greens etc.
Using this then, we can compare annual kg CO2e footprints of various diets. Let’s define the following diets ranging from ‘heavy meat eating’, which is eating meat 10x per week, all the way to ‘vegan’ where those 10 meals have been substituted for non animal-based alternatives.
Right. Data dump. So what does this show?
- the left-most column at the top is our global average kg CO2e estimates from PN2018 for a 50g protein portion of each food type
- the top right table is our assumed weekly frequency of consumption of each food in each diet e.g. a ‘Heavy Meat’ diet contains 3x weekly beef, 4x weekly chicken etc
- the bottom right table then shows the annualised kg CO2e of these food choices and then their sum e.g. an ‘Avg Meat’ diet emits 2,378kg each year just from considering those 10 meals. The overall footprint of the whole diet will be a bit larger. But we don’t need to worry about that because we’ve assumed it’s the same add-on for all diets.
Can we make any immediate observations?
- using the numbers we have and the constructed diets, annual CO2e decreases as we consume less meat
- this might not be the case if the diets were constructed slightly differently e.g. a pescatarian chomping down on cheese and prawns may outweigh a conscientious white meat eater
- looking at the ‘Heavy Meat’ diet, eating 4/10 meals of red meat makes up 75% of the CO2e footprint for those 10 meals
But as mentioned the above numbers are not for a whole diet, just the 10 meals we have chosen to look at. What we really care about is the difference between these 10 meals i.e. what is the difference in annual CO2e from eating these 10 meals according to the ‘Heavy Meat’ diet compared to e.g. veggie/vegan? For that we construct a matrix of diet changes below.
This shows the annual kg CO2e differences between these diets e.g. the ‘Vegan’ diet ‘saves’ 3,760kg CO2e each year vs the ‘Heavy Meat’. Do these numbers seem ballpark sensible? Yes.
- on average what we eat makes up 25% of our carbon footprint
- the UK average footprint is around 14,000 kg each year
- by that logic, we would expect the CO2e for a whole diet to be around 3,500kg each year
- the remaining diet footprint (outside of the 10x meals) can be assumed to clock in at around an extra 1,500kg each year from fruit/veg/carbs
So our numbers look potentially slightly high, but by and large they’re in the right ballpark and there are no obvious blunders or calc errors (given ‘Avg Meat’ clocks in then at around 3,800kg total including all other consumption). Now we have some numbers for the changes from diets, let’s calculate some numbers to compare them to from the other things we get up to.
Cruisin’ Around
What about all those fumes spewing from exhausts and airplane jet engines? How do they stack up against the numbers we’ve calculated above?
Return Long Haul Flight: 3,500kg
This is assumed around 10,000 miles and like flying return from London to California/Buenos Aires/Hong Kong in economy class (fancier classes have a higher footprint as they take up more space on the flight).
Return Short Haul Flight: 500kg
This is assumed to be like a city break-esque journey of around 1,000 miles like flying return from London to Barcelona/Milan/Berlin.
10 mile (5 each way) daily commute in avg UK non-electric car instead of bus: 1,740kg
Obviously we need to get around, especially to and from work, and so the comparison here is getting a bus instead of driving. Also important is that congestion, as MBL points out, roughly triples the emissions through:
- a doubling of your own
- increasing those of those around you by adding to the congestion
I’ll assume here that 75% of the commute is un-congested with 25% congested. The bus comparison will be using MBL’s calcs for those of a half-full London Routemaster. The car calcs also include the embodied emissions of the car i.e. the (correct) assumption is that you wouldn’t need the car or the embodied carbon in it.
7,000 miles driving around Europe in a 2nd hand 2004 VW Golf: 2,450kg
A personal example from me of buying an old second hand car (avoiding the embedded emissions in the car manufacture if it was going to scrap) and whizzing around Europe in it.
What about fashun honeeyyyyyy?
There have been various attempts to produce an LCA type study of the fashion industry’s carbon footprint with some estimates putting it globally at 10% of total emissions. There are many problems with the fashion industry, particularly ‘fast fashion’, but when it comes to purely CO2e it doesn’t seem to stack up too badly. Nevertheless, let’s create a few examples to contextualise.
Modest Shopping: 137kg
Assume that we buy:
- 5 new t-shirts/tops each year
- new shoes each year (across running shoes, work shoes, trainers etc)
- new jumper each year
- new jeans/trousers each year
- new jacket every other year
Shopaholic: 1,320kg
Assume that we buy:
- new t-shirt/top every week
- new shoes every month
- new jumper every month
- new jeans/trousers every other month
- new jacket every 3 months
So how do these roughly come out in terms of CO2e? We can make use of MBL’s numbers along with a few estimates here and here to help corroborate our ballpark estimates. It’s worth noting that the more ‘fast fashion’-y it is the more likely that the footprints could be higher due to flying of the materials instead of the much lower carbon shipping alternative.
Everything else
And finally a few select examples from me to round off the picture and give us hopefully what is now a fairly wide range of comparatives before we display this with some nice visuals.
Dropping your phone: 63kg
Or any other way of carelessly wasting your iPhone. Phones are made from stuff and that stuff needs mined/created, assembled and retailed.
Using a tote bag every day for 5 years (instead of a plastic bag): 16.75kg
Despite reducing the use of single use plastics, totes are not exactly a good solution. In fact, they’re a bad one. But a bad one that you can sell for £20.
Drinking 1l of bottled water a day instead of tap water: 146kg
I have and never will understand people’s obsession with bottled water but for the sake of argument this could also be just buying bottles of water/coke when on the go.
Weekly Friday takeaway margarita pizza: 115kg
A tradition my mates indoctrinated me into during Lockdown 1.0 in a bid to determine South London’s best pizza. The assumption here is that you live 2 miles from the pizza place and get a standard margarita pizza. The cheese is what largely makes up the footprint here. White ‘pizzas’ tend to have more cheese. So if ever you needed another reason to swerve them, there it is.
4 pints at the pub on a Friday: 189kg
Yeeeeeesssss laadddsss. There isn’t a massive difference on whether it’s in a pub or from a supermarket but interestingly given the weight alcohol is one of those areas where the distance it has to travel does have a (noticeable) impact on its CO2e. As MBL points out, for that reason tinnies over bottles are the environmental choice due to their less hefty build.
Daily takeaway oat milk cappuccino: 145kg
Exactly as described. A takeaway coffee in a takeaway cup every day for a year (although the takeaway cup doesn’t add much). Similar to the above tote vs plastic, bringing your own reusable cup doesn’t change the CO2e picture much (probably worsens it actually unless you’ve been reusing already since 1982).
Breaking your mate’s laptop at an afterparty: 326kg
Carelessness costs. In the case of a 13inch MacBook pro, it costs both economically and environmentally. Fortunately, this is one area where capitalism comes to the rescue as there are cheaper ways to waste the planet than buying and chucking beer over Apple’s finest produce.
So how does it all stack up?
Let’s try to recruit some visuals now to help us visualise all the above numbers before trying to make some conclusions.
So before diving into comparisons let’s make sure the above is crystal:
- the chart shows the kg CO2e per activity with each category (other, travel, fashion) colour grouped
- horizontal lines mark on the calculated annual ‘CO2e savings’ of a select few dietary changes from our above matrix of changes
How exciting!!! It feels like (in theory) we are close to answering our original question. It’s worth remembering that we’ve made some assumptions to get to this point (that are about to go under the cosh), but still we have some pretty insightful comparisons. Under the assumptions that we have made:
- yes, it seems like dietary change is one of the largest things you can do as an individual to reduce your impact on global warming through CO2e
- no, it’s not clear as day — it looks like depending on your transport habits there are other activities that could make a substantial difference
- reducing meat consumption from lots-to-some has a bigger impact than modest-to-veggie and veggie-to-vegan
- tote bags are fashion statements not environmental solutions
- carelessness with your possessions (iPhone, Mac) could ‘cost’ you the savings you made from a year of forgoing Greek yoghurt and mozzarella-laced pizza.
But overall, yes. Under the assumptions we’ve made, yes it does matter. It’s clear that ‘travel’ also sticks out with those relatively large looming orange bars, especially when we compare to the other non-diet related items, but we have some conclusions which is pretty cool. Now the task is to see if those conclusions persist once we start removing the assumptions and bringing the analysis closer and closer to the real world. Or if the picture returns to become murky again. Let’s go one by one and see.
