For most of us, food shopping involves the local supermarket and in that respect Tristram Stuart isn’t any different, except you won’t find Stuart at the checkout instead he’ll be round the back rummaging through the supermarkets bins for his food. Stuart is one of a growing band of freegans who protest against global waste – Stuart’s got a point about waste:

Most people would admit that wasting food is not good. But surely, they’d say, the problem can’t be that serious? Isn’t rooting around in rubbish bins a somewhat extreme – and unpleasant – reaction? Stuart would disagree. In his new book, Waste: Uncovering the Global Food Scandal, he sets out in forensic detail exactly why we should all be worried by the problem. In his view, food waste is the big unspoken environmental crisis of our times, right up there with more familiar concerns such as deforestation, water scarcity, even global warming.

Addressing food waste, he says, is a vital step when it comes to sorting out many of these other problems, and it’s hard to disagree with his logic. If we waste less food, we’ll need less land to grow it on, and hence will cut down fewer trees; we’ll use less water to irrigate that land and less carbon to transport and process the food it produces. On a more basic level, food waste is an issue of equality. If we didn’t waste so much food, there would be more available, which means fewer people in the world would go hungry.

Much of the evidence that Waste uncovers is startling. In Britain, we are remarkably profligate with our food. Most of us are probably used to laughing about our personal failings – that packet of pre-washed lettuce turned to mulch in the fridge, that half-eaten loaf gone mouldy in the bread bin. But when such individual wastefulness is aggregated, the figures become less amusing. A 2008 survey by the waste organisation Wrap, based on studying a sample of household bins, found that we collectively throw away 6.7m tonnes of food each year. (Stuart, in fact, says that the Wrap figure is too high, because it includes things like orange peel, but his estimate for “avoidable food waste” is still 5.4m tonnes.)

An easier way to get a handle on this is to think in terms of individual items. As a nation, we chuck away 484m unopened yoghurt pots each year, 1.6bn untouched apples (or 27 per person) and 2.6bn slices of bread. That doesn’t even include the food we waste at work or leave on our plates in canteens and restaurants. All in all, we chuck away roughly a quarter of the food we buy.

What many of us don’t properly realise is that this consumer waste represents just the tip of the iceberg. Although individuals contribute a massive amount to food waste, even more occurs further back along the supply chain. A huge amount is wasted during or immediately after harvesting, especially in developing countries, where poor transport and other infrastructure mean that food often perishes before it gets to market.

Then there are the unwieldy and complex workings of the global supply system: to get from its source to our plates, much of the food we eat undertakes a journey of epic proportions, involving carts, ships, planes and lorries, warehouses, processing plants and supermarket distribution centres. At each stage of this journey – inevitably, perhaps – a proportion gets wasted. When all this is added together, Stuart says, it is possible to estimate that more than a third of global food supplies is wasted (with the proportion in rich countries being as much as 50%). At the same time, nearly a billion people on the planet live close to starvation. William Skidelsky, The Observer.

See food waste is killing us – still I couldn’t rummage through the bins like Stuart.