Says Chris Goodall, author of How to Live a Low-carbon Life, “Driving a typical UK car for three miles adds about 0.9 kg of CO2 to the atmosphere. If you walked instead, it would use about 180 calories. You'd need about 100grammes of beef to replace those calories, resulting in 3.6 kg of emissions, or 4 times as much as walking. ”
Recent research, summarised in the New Scientist magazine (18th July 2007), suggests that modern methods of intensive beef production generate large amounts of greenhouse gases. This is not a new hypothesis: we have gradually become aware of the huge amounts of grain needed to feed our animals, and of the troublesome amounts of energy needed to produce the fertiliser needed to get our cereals to grow. The scientist David Pimentel has suggested that it takes seven times as much grain to feed all meat animals in the US as it does to directly feed the human population. The new research suggests that one kilogramme of meat creates the equivalent of over 36kg of global warming gases.
The average person in the UK eats about 12 kilogrammes of beef a year. So eating a typical amount of beef generates 0.4 tonnes of emissions. After including the impact of international aviation, each UK citizen is responsible for about 12 tonnes of emissions from all sources, including industry. A simple sum shows that beef, a relatively small part of many people's diet, accounts for between 3 and 4% of the typical UK person's carbon footprint.
This is bad enough. But looked at another way, the impact of our food production becomes even clearer. A simple calculation shows that industrial food production is more destructive of the global atmosphere than driving a car. In particular, if one walks to the shops, and eats something after the walk to put back the calories lost in the exercise, then it would generally be better to drive instead of walk. The greenhouse gas content of the top-up food may well be greater than the emissions from the car.
Walking three miles uses about 180 calories. Replacing the energy used, assuming you don’t want to lose weight, would mean eating about 100 grammes of beef. Of course, it depends on the cut of meat, and how much fat it contains, but this figure is reasonably typical of beef in British shops. The scientists in Japan give a figure of 36 kg of emissions for a kilo of meat, so a portion of 100 grammes equates to about 3.6kg. This is the first part of the calculation – it shows that one 3 mile walk generates 3.6kg of emissions if one replaces the energy lost with beef.
What if one drove the 3 miles instead, and so didn’t need the extra food? The average UK car emits about 290 grammes (0.29kg) of CO2 for every mile travelled. A 3 mile trip therefore generates 0.87 kg of emissions. This is about a quarter of the equivalent emissions from walking. And if there are two of you, and you share the car, then walking would be eight times as bad for the climate.
The troubling fact is that taking a lot of exercise and then eating a bit more food is not good for the global atmosphere. Eating less and driving to save energy would be better.
Modern agriculture is extraordinarily energy intensive. And it is not just energy. Cows belch gallons of methane every day and methane is a fiercer global warming gas than CO2. Manure and fertiliser also give off smaller quantities of nitrous oxide, which has over 300 times the impact of CO2.
Intuitively we recognise that major industries such as aluminium smelting generate climate changing emissions. But making a kilogramme of aluminium – one of the most energy intensive processes used today – creates only about 6kg of CO2 if fossil fuel is used compared to 6 times as much for food.
Says Goodall, “We need to become accustomed to the idea that our food production systems, particularly those involving ruminant animals and their methane burps, are equally damaging. As the man from Ryanair says, cows generate more emissions than aircraft. Unfortunately, he is right. Of course this doesn’t mean we should always choose to use air or car travel instead of walking. It means we need urgently to work out how to reduce the greenhouse gas intensity of our foodstuffs.”
Gudrun Freese | alfa
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