Where I live, we all had one of the below stickers slapped on our black bins near the end of last year. Now, the overall sentiment of reducing food waste I completely agree with. However, I was very struck by the bold statement on this sticker that wasted food ‘accounts for more emissions than flying!’ – what??! Surely this cannot be true, I thought...
I always like to do my own sums in such situations, so first I followed up the link on the sticker to the website outofdate.org.uk: They make this comparison with flying on their ‘Environment’ page, where they point out that 25-30 per cent of greenhouse gases are created by food production alone, and say ‘to put this in context, wasted food produces six times the amount of greenhouse gas emissions as global aviation’ – which they illustrate with a handy pie-chart, as replicated here. BUT, oh dear: they’ve totally messed up their calculation here by confusing emissions from wasted food with emissions from food production as a whole, and in doing so vastly exaggerated the global emissions from wasted food.
By how much have they exaggerated this comparison with their calculation error? I’ve been drilling down into the various big numbers given for different types of food and working out what these really mean in terms of per-household emissions. In the ‘Facts’ section of the website, bread, potatoes, poultry and tomatoes are all explored in terms of how many hundreds of thousands of tonnes of CO2e emissions they generate. CO2e stands for ‘carbon dioxide equivalent’ which is a measure that scientists have devised in order to include not just carbon dioxide (CO2) but also other greenhouse gases which are methane, nitrous oxide and ozone. The term expresses them collectively in terms of CO2 based on their relative global warming potential – thus giving a fuller picture of the impact of any particular activity, not just the pure carbon dioxide emissions.
The figure given for wasted bread is 318,000 tonnes of CO2e emissions per year for the whole of the UK; 1 tonne is 1000kg. There are 28.3 million households in the UK, so dividing the total UK figure by 28.3 million, this equates to an average figure of 11kg of CO2e emissions per household, per year, for their wasted bread. Similar figures are given on the website for potatoes, poultry and tomatoes, which when converted to ‘per household’ figures come to 11.5kg, 14kg, and 4kg CO2e emissions respectively for the typically wasted amounts of each of those food items, per household per year.
Although both are expressed in kilograms, the weight of the food itself and its amount of CO2e emissions are not directly related – it all depends of course on how each food item is produced and transported. For instance, potatoes are deemed to have emissions roughly half their actual weight, whereas poultry’s CO2e emissions seem to be nearly four times the weight of the poultry itself. So, although the website does give a total figure for the weight of food waste in the UK (which works out to 159kg per household, per year) it’s very hard to be accurate about what that equates to in terms of CO2e emissions: best case, if all the waste were like potatoes, then it would be around 80kg CO2e; worst case, if all the wasted food were like poultry, then it would be around 620kg CO2e emissions per household, per year. The true figure for average household annual food waste emissions will be somewhere in the wide range between 80kg and 620kg CO2e emissions.
OK, so how does all that compare to whatever flying our typical household might be doing every year? Checking against a flight carbon calculator (I’ve used the ICAO one): if our typical household contains four people and they take, say, one family holiday by plane from London to Malaga, their return flights would create emissions of 1100kg CO2e in total. So that's 100 times the emissions of the whole of their presumed annual bread wastage. It’s nearly double our most pessimistic estimate of their total food waste emissions, and more than ten times our most optimistic estimate. And that’s just one short-haul flight for the whole family. What if they fly to Europe more than once a year? What if they go somewhere long-haul? What about extra business trips? Well in that case their household emissions from flying would completely dwarf anything they might save by making sure all the bread and bananas get eaten up. The bottom line is: flying generates huge amounts of avoidable greenhouse gas emissions. These annoying stickers seem to give the false impression that flying isn't so bad after all, as long as you eat a toasted crust every now and then rather than binning it. So wrong!
The final thing to point out regarding food waste emissions is that of course those emissions from food production are exactly the same whether you and your family eat the food or not! If we all continue to buy the same amount of food each week but just make sure that it does all get eaten up, then the only thing that will change is our waistlines. You cannot save emissions from reducing food waste unless you do actually buy less food as a result of reducing what’s wasted. We all need to eat to live, and it’s great to try and do so as sustainably as possible. But don’t let fretting about food waste distract you from tackling the really big culprits in terms of your personal, avoidable emissions, and that is transport in general, with flying as the very biggest emitter.