And you thought the carbon footprint debate was simple!
The carbon emitted in producing green beans in Kenya and importing them can work out as less than is emitted by driving to the supermarket to buy locally produced beans
I'm old enough to remember a world when carbon didn't dominate discussion. I knew about the carbon cycle from my school days, how plants absorb carbon dioxide, keep the carbon to build themselves, and then exhale the oxygen for you and me to breathe. It was all so clear, all so tidily explained.
The 21st century has started with a carbon footprint. We all have one, businesses have one, countries have one. And the one thing we've learnt through television, radio and print media is that putting carbon compounds into the atmosphere is a bad thing.
If the more extreme doomsday pundits are to be believed, this careless behaviour of unhesitatingly emitting carbon compounds, even when we breathe, is contributing to a global warming so sudden, that soon all the ice on the planet will melt and our coastal cities will be under 50 metres of sea water.
As in all debates, there are those who take the opposite view, but the general consensus is clear: if we continue to emit carbon compounds through industry and transport, the world will get warmer and sea levels will rise.
Throughout this debate we've begun to ask ourselves what we can do to avert a crisis. Fingers have been pointed at the transport industries, especially the growth in airline traffic, and energy sources like fossil-fuel electricity generating plants. Changing major systems like these can't be done quickly, so what can we the consumers do to play our part?
One of the strategies that has been vigorously proposed by ecologists has been avoiding food miles. If you've managed to miss this particular debate, it goes like this: food transported from far-off countries should be avoided in favour of local produce.
Since less fuel will be used in distributing local food, less carbon will be released into the atmosphere. Some supermarkets have begun putting little aeroplane symbols on produce that has food miles, to help the consumer decide whether or not to buy it.
Like the bleat of the sheep in Animal Farm, this has become a mantra -- food miles baaaaad, local food good. It's very simplicity is its attraction. We can do our bit to prevent global warming simply by buying food that has fewer food miles.
If only life were that simple. When it comes to food production and distribution there's complexity inherent in the systems that isn't immediately apparent. Consider this. If the supermarket you drive to is more than three miles away, then you'll emit more carbon compounds from your car than it took to bring a packet of beans from Kenya.
Okay, you're not going to go to the supermarket for just a packet of beans, but it does make a point. What you need to consider is that local food can sometimes be less carbon-friendly than imported foods.
If you live in Ireland and want to eat green beans you have two choices -- imported beans or locally grown beans.
The green beans from Kenya have got here using aviation fuel and thus have carbon dioxide emissions tied to them. But when you examine this closer, you find that in Kenya, bean production is almost entirely done with manual labour, the only fertiliser is cow dung and the only heat used to make the beans grow is sunlight.
Simple irrigation systems with gravity-feed waters the plants and many Kenyans get gainful employment in food production.
Weigh that up against beans that are grown under glass, that use heating systems, use agricultural machinery that burns diesel, use pumps to irrigate and use oil-based artificial fertilisers, then we come to the counter-intuitive conclusion that in this case at least, the Kenyan beans account for less carbon emissions than our local ones.
The problem is that the concept of food miles is just too simple; it can help us understand how much carbon has been emitted in the transport of the food, but it doesn't help us assess how much carbon has been emitted during the entire process of that food's production.
Take the humble apple. It seems a no-brainer that local apples are going to have less carbon emissions attached to them than those flown in from overseas. Apples mature as autumn fruits, they are picked in September and October. During those months you can buy locally produced fruit that will have very little carbon emissions attached to it.
But as the months go by, that autumn glut of fruit is stored in chill warehouses which, of course, use fossil-fuel energy to power them.
When you do the maths on this you find that by the following August those stored apples will account for more carbon emissions than apples shipped in from Australia and New Zealand. So to be carbon-conscious, you should buy local apples in the autumn, winter and spring, and imported apples during the summer.
Much the same applies to lettuce. During the winter lettuces are grown here under glass or in polytunnels and they need to be heated. Any heating system other than solar will produce some carbon emissions, so lettuces grown outside in hot countries will be carbon-friendlier than those produced under glass here. In the winter buy imported lettuce, in the summer months buy local. In these cases your best strategy to combat global warming depends on the seasons.
Last year the Soil Association, the body that certifies foods as organic, made an announcement that it was going to stop endorsing organic foods that had been transported by air. Recently it has dropped this plan, and it continues to endorse imported organic foods that meet its ethical standards.
The simple clarity that food miles are bad is increasingly being challenged. It's not that the concept is wrong, it's just that it's too simplistic.
A new idea that's being promoted is a carbon label, which tells the consumer how many grammes of carbon dioxide have been emitted to produce a product from start to finish.
In the UK, Tesco has begun putting carbon labels on around 30 of its own-brand products, ranging from vegetables, to fruit juice, to crisps and light bulbs.
Clearly these aren't simple calculations. To quote Graham Sinden of the Carbon Trust: "You have to take into account emissions that occurred in the farmyard, for example. Cows and sheep produce methane, which is a far more damaging greenhouse gas than carbon dioxide. Similarly, fertilisers produce nitrogen oxides that are also dangerous. Then you have the issue of transport and processing.
"Cooking is another factor. That requires heat that in turn releases carbon dioxide. After that you need to store products. That often requires refrigeration, which requires electricity, which releases carbon dioxide.
"Estimating how long a product will be kept in a store and how efficient is its refrigeration is not easy to assess, but it has to be done.
"Then you have to work out how long your product will be kept at home once it has been purchased. You also have to estimate how efficiently it will be cooked.
"And finally you have to work out how much carbon is involved in its packaging and how much will be emitted in disposing of those wrappers and labels once discarded."
Being an eco-warrior has got more complicated.
Even if carbon labelling can be done, we're still left with another ethical dilemma -- can we really continue to keep poor countries poor by refusing to buy their produce on the basis that transporting it has too high a carbon cost?
- Paolo Tullio
