CO2 footprint of food: Notion of 'seasons' all but obsolete
Which strawberries have the higher carbon footprint, those grown in the blazing suns of Africa and jetted into Europe, or those grown in bleak midwinter albeit under glass and heated by local energy? The answer might surprise you, writes Ian Duncan.
I grew up in berry country. Acres of fields surrounded my home town of Alyth and I have many memories of picking strawberries.
For those of you who have never picked berries, this might seem like a gentle recollection of youth.
For those of you who have, it will register as some sort of low paid summer indenture. Ankle-high bushes bleeding crimson juice that could barely be removed with bleach. No fun for a tall teenager. Strong sun or strong rain. And at the end of it all, you had earned enough money to buy a new school uniform for the year ahead.
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Setting aside the realities of the berry harvest - which coincidentally is now mainly in the hands of migrants from eastern and central Europe - I was recently struck by a berry important issue.
The other week I found myself in an 'hypermarché' in Brussels. There I found a punnet of locally-grown strawberries, and since it was February, I think I was fair in assuming that they were grown in a glasshouse. The previous week I had found a similar punnet of strawberries in Edinburgh, this time imported from Egypt.
When I was growing up, the berry season ended just about the same time as the summer holidays (which is no coincidence). Thereafter, strawberries could only be enjoyed in jam. Nowadays we eat berries all year round, the notion of 'season' all but obsolete.
So, here is a question for you: which strawberries have the higher carbon footprint, those grown in the blazing suns of Africa and jetted into Europe, or those grown in bleak midwinter albeit under glass and heated by local energy?
In Belgium, some 500 acres of glasshouses are devoted to berry culture, with computer-controlled irrigation, fertilisation, and a (CO2-enriched) climate. Each square foot of greenhouse yields one pound of strawberries. The Belgian winter season delivers three yields (higher than the comparable yield for a traditional 'summer' season), with no berries lost to pests or weather. Some 3.5 per cent of all strawberries consumed in the EU are grown in Belgian glasshouses.
Now contrast this with Egypt, from which my Edinburgh supermarket-bought berries originated. There the season lasts from November to February. With an average temperature of 18 degrees, no artificial heat is required to nurture the berries. The loss to pests can be higher, but horticulturalists address this through greater use of pesticides.
So, the key question, all things being equal, do the berries grown in Africa and flown to Europe in a jet plane have a higher or lower carbon footprint than berries grown in Europe under hothouse conditions?
Well, studies demonstrate that strawberries grown under glass emit on average 4kg of carbon for every 1kg of fruit produced. For every 1kg of strawberries grown under natural sunlight, the equivalent quantity of carbon emitted is only 0.8kg.
Added to this, of course, is the carbon cost of transport. To transport 1kg of strawberries on a jet plane from Egypt to Scotland would result in 0.19kg of carbon emitted. This figure fluctuates with the distance between country of origin and country of consumption.
So the total carbon emission figure for 1kg of strawberries grown under an Egyptian sun is 0.99kg per 1kg of fruit produced, effectively a quarter of the carbon emission of the hothouse berry.
Of course, the lowest figure of all in terms of carbon emissions would be strawberries grown close to market under natural conditions. That means that the lowest carbon emissions are from Scottish strawberries grown in season. Out of season, if you want strawberries, there is always jam.
And for those of you interested in the eating in season, Eat Seasonably (http://eatseasonably.co.uk/) have produced a handy guide.