You Might Be Wasting Food, Even If You’re Not Throwing It Away

, scientific adviser, Climate and Energy | November 29, 2017, 10:24 am EST
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When I was a child, I was often told not to waste food. Phrases like “Clean your plate or no dessert,” and “Just cut out that little spot. It’s a perfectly good banana,” and “Don’t put that in the back of the fridge. It’ll spoil and then we’ll have to throw it out.”

Now, half a century later, food waste has grown from family stories into a worldwide policy issue. A common estimate is that 40% of food is wasted. Scientific papers analyze consumers’ feelings about the sensory and social qualities of meals, and reducing waste is becoming just as much a concern as local, organic, and community-supported. This issue is critical. Yet an important part of the food waste problem remains unseen.

This additional waste involves not the food that is thrown out because no one eats it—but the food we do eat.

Recent studies by an international group of researchers led by Peter Alexander of the University of Edinburgh have shown just how important this additional kind of waste is. Alexander and his colleagues have published a series of papers that give detailed, quantitative analyses of the global flows of food, from field to fork and on into the garbage can. The results are striking. Only 25% of harvested food, by weight, is consumed by people. (Measuring food by its energy values in calories or by the amount of protein it contains, rather than by its dry weight, does increase the numbers but only a bit—to 32% and 29% respectively.)

But beyond these overall figures, Alexander and colleagues point to the importance of two kinds of waste in the ways in which we do eat our food, but in an extremely inefficient way. One is termed “over-consumption,” defined as food consumption in excess of nutritional requirements. (For the purposes of this discussion, I am referring to food consumption in excess of caloric requirements. However, it is critical to note that calories consumed only tells a small part of the story. A complete analysis would include the quality of the foods consumed and the many systemic reasons why we “over-consume”—including the structure of the food industry, the affordability of and access to processed foods relative to healthier foods, etc. But that is the subject for several books, not one blog post.)

Even using a generous definition of how much food humans require—e.g. 2342 kcals/person/day, compared to the 2100 kcal used in other studies—Alexander et al. find that over-consumption is at least comparable in size to the amount of food that consumers throw out (“consumer waste”). This is show in the graphic below, in which in each column, the uppermost part of each bar (in dark purple) represents over-consumption and the second-to-the-top section (light purple) shows consumer waste.

Losses of harvested crops at different stages of the global food system. The four columns represent different ways to measure the amount of food: from left to right, by dry weight, calories, protein, and wet weight. Source: Figure 4 of Alexander et al., 2017, Agricultural Systems; DOI: 10.1016/j.agsy.2017.01.014.

So, it turns out that for many people, reducing consumption could improve health while also potentially saving food and therefore also the many resources that go into growing and distributing it.

But neither overconsumption nor consumer waste are the largest way we waste the resources that can be used to produce food. That turns out to be livestock production—the dark red sections in the graphic above. Livestock are an extremely inefficient way of transforming crops (which they use as feed) into food for humans, with loss rates ranging from 82% (in terms of protein) up to 94% (by dry weight) once all of the feed they consume during their lifespans is considered. It’s not food that goes into our garbage or landfills, but it represents an enormous loss to the potential global supply of food for people just the same.

The reasons have to do with ecology: when we eat one level higher on the food web we’re losing about 90% of the edible resources from the level below.

Achieving the ultimate goals of reducing food waste—for example, reduced environmental consequences and ensuring more people have access to foods that meet their nutritional requirements—of course will require additional and critical steps. For example, additional food doesn’t help if it isn’t nutritious or can’t be accessed by the people who need it. Also, spared land doesn’t help if that land isn’t managed in a way that contributes to a healthier environment. However, thinking more about all types of food waste can help us to find better ways to protect our natural resources while producing and distributing healthy food for all.

The results of these new analyses should expand what we think of when we hear the words “food waste.” Yes, it includes the food we buy but don’t eat—the vegetables we leave on our plates and the bananas we throw into the compost bin—and it’s very important to develop habits and policies to reduce this waste. But we also need to confront the wastefulness in what we do eat, by asking: how much and what kind of food should we be buying in the first place?

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  • Ville Karinen

    Important article. But does it make sense systemically, if we will eat the plate empty? That way we will be more likely to take too much next time as well.

    It would nice to have easy blood sugar measurement before meal and during that as well, combined to analysis of food before it is on our plate, or eating little by little, like sushi or tapas meals. The plate might be a bad innovation, or plates should be modular.