Carbon footprinting: time to pick up the pace

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Euan Murray grew up on a sheep farm in southern Scotland; now he is in charge of “carbon footprinting” for corporate clients of the Carbon Trust. “If I ask my old man, ‘What’s the carbon footprint of a sheep?’ he looks at me as though I’m mad,” he explains. “But he can tell me the stocking density, what he feeds the sheep, and he can answer those questions as part of running his business.”

Quite so. Carbon footprinting, the study of how much carbon dioxide is released in the process of producing, consuming and disposing of a product, is all about the specifics. This is a refreshing change from the politics of climate change, which is all about the generics. We hear promises from our leaders of big change in the future, without any credible plans right now.

I first approached Murray to ask him about the climate change impact of a cappuccino. Loyal readers may recall that a year and half ago, I wrote about the question, pointing out that meeting any of these grand targets in a sensible way would require billions upon billions of small decisions. The cappuccino’s climate change impact depends on whether the café is double-glazed, the decisions the staff and I take to get there, the diet of the methane-producing cow that produced the milk and the source of power for the espresso machine. Last week I pointed out that there are around 10 billion products in a modern economy; that means that the problem of reducing carbon dioxide emissions is “simply” the problem of reducing carbon dioxide emissions from a cappuccino, 10 billion times over.

In the case of the cappuccino – or at least, a typical, generic cappuccino – the climate change impact probably comes from the milk. I say “probably” because we don’t know for sure. Murray’s best guess was based on his work on milk chocolate. Milk makes up one-third of a chocolate bar by mass, but is responsible for two-thirds of the climate-change impact of the entire production and consumption process. Switching to espresso might be in order; so, too, might a different diet for the cows. It is hard to make generic recommendations, though: even the particular soil on which the grass grows on which the cows feed alters the climate change calculus.

The carbon-footprinting process often produces surprises. An environmentally conscious consumer in the crisps aisle of the supermarket will probably be thinking about packaging or “food miles”. The Carbon Trust reckons that about 1 per cent of the climate impact of a packet of crisps is from moving potatoes around. The largest single culprit is the production of the nitrogen fertiliser, and half of the climate impact in general takes place at the agricultural stage. The point is not that agriculture is always the problem, but that it is very hard for a well-meaning consumer to work out what the green purchasing decision actually is. For this reason, the Carbon Trust has a carbon labelling scheme. The trouble is that many consumers simply do not care enough to pay more or choose a less enjoyable product simply because of the low carbon label.

A government role is necessary, then, but it is even harder for governments to regulate such fine details. All this is why economists continue to advocate some kind of carbon price, which would give an incentive to everyone involved in these complex supply chains to trim carbon dioxide emissions. A modest and credible price for carbon is slowly becoming the conventional policy wisdom. It is a shame we still don’t have it.

By Tim Harford

Tim Harford’s new book, “Dear Undercover Economist” (Little Brown), will be published on August 7.