SOMETIMES you want to make a decision that helps the planet. Maybe you鈥檙e selecting an electricity supplier, choosing whether to sign a petition against wind farms or wondering whether to install solar panels. The right option might seem obvious: who could argue with the green credentials of a solar panel, for instance? But such decisions are often harder than you think.
Often the problem comes down to hidden energy. Energy is most obvious when it is kinetic, producing a visible effect such as when you kick a ball or wrench open a door. But energy is also needed to make things, and is locked up, or 鈥渆mbodied鈥�, in all sorts of manufactured matter, from a metal pipe to a slice of pizza.
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Take buying a car 鈥� a big purchasing decision that could have a more significant impact on your carbon footprint than most. Say you鈥檝e decided to swap your old petrol-powered banger for a new, fuel-efficient version. If your current car was manufactured a decade ago, it might typically pump out about 1.8 tonnes of carbon dioxide a year, if you drive an average sort of distance of 12,000 kilometres. If you were to buy the most fuel-efficient model you can find on garage forecourts today, and drive a similar sort of distance, you鈥檇 emit about 1 tonne annually, according to company-declared emissions at least.
鈥淭hey might seem easy, but few green choices are as straightforward as they first appear鈥�
That seems like a worthwhile saving, but crucially we鈥檝e yet to consider the energy embodied in the car. It takes energy to run the machines that built it and to produce the materials that form it, and this also generates CO2. According to manufacturers鈥� figures, the process of making a car typically takes between 600 and 800 kilograms of CO2. Factor in making the steel for the body itself, and you can add in another tonne of emissions. Add in the carbon footprint of the aluminium components 鈥� which require five times more energy to smelt than steel 鈥� plus upholstery, glass, rubber and electronics, and your new car clocks in at around 6 tonnes of CO2, . You鈥檒l have to run it for at least eight years to recoup its carbon cost.
Faced with such figures, you might consider going the whole hog and buying an electric car. Here the same sorts of embodied emissions will be involved as with the petrol car, but at least there are no emissions from the exhaust, right? Sure 鈥� but if, when you plug the car into the mains, it is sucking power from a carbon-belching coal-fired power station, it has merely shifted its emissions elsewhere.
So beware: manufacturers will often try to play on your sense of environmental responsibility, but few green choices are as straightforward as they first seem. With a solar panel, what is the emissions cost of making the slab of highly purified silicon it鈥檚 probably made of? Or of the huge magnets that help harness the energy from a wind turbine?
Asking such probing questions can give you a whole new perspective on a range of decisions, for example what you eat. Say you live in the UK, and you have a choice of a locally grown tomato or one grown in Spain. It鈥檚 common to think the green option is to limit the food miles travelled and go for the local produce. But the embodied emissions associated with heating the hothouse in which the UK tomato was grown might easily 鈥� depending on how the Spanish tomato was freighted in, by air or by lorry 鈥� trump the embodied emissions associated with transport.
Such considerations rarely make our decisions easier. If you opted to ditch the new car entirely and cycle to work instead, for instance, what is the carbon cost of shipping in all those extra veggies to power your leg muscles? But then no one said saving the planet was easy.
Like this? Read: 鈥�Get smarter: 9 ideas to make your life better鈥�
This article appeared in print under the headline 鈥淣eed to know: Hidden energy鈥�
