What a waste of potatoes

Food waste is a hot topic, and the humble potato is a disproportionate victim of our wasteful ways. In England, around two-thirds of potatoes end up in the bin. A study has now shown that the Swiss are not much better, discarding more than half of their potato harvest somewhere between field and fork.

The study, conducted by researchers from Agroscope and ETH Zurich, and published in the journal Waste Management, is the most extensive research ever produced in Switzerland on food waste of a single product — breaking down the losses of the staple food along the entire supply chain, from producer to wholesaler, retailer, processor and consumer level.

The researchers recorded the quantities both of table potatoes and of processing potatoes, which are processed into chips and crisps. They also compared the losses that occur in organically and non-organically produced potatoes in both categories.

One in two potatoes thrown out

From the field to the home, 53% of conventionally produced table potatoes are wasted, and this figure rises to 55% for those produced organically. For processing potatoes, the figures are lower: 41% of organic potatoes are discarded, compared to 46% from conventional production. The higher waste proportion for conventionally farmed processing potatoes is attributed to the overproduction of this crop, which rarely occurs with organic farming.

Waste is greater for organically farmed table potatoes because these fail to satisfy the high quality standards more often than conventional ones.

Farmers discard a quarter

Up to a quarter of the table potato harvest falls by the wayside at the producer stage. A further 12–24% are rejected by wholesalers during sorting. Just 1–3% fall between the cracks at retailers, and a further 15% are wasted in households.

Although private households account for a relatively small proportion of potato waste, ETH doctoral student Christian Willersinn, who works in the group led by Michael Siegrist, Professor of Consumer Behaviour, together with colleagues from Agroscope, said their contribution has the most impact: in private homes, most of the unused potatoes end up in the bin bag or on the compost heap. Producers, traders and processors, on the other hand, recycle the vast majority of waste into animal fodder or, to a lesser extent, into feedstock for biogas plants.

Quality standards and specifications

According to Willersinn, the blame lies primarily with consumers’ high quality standards, especially when it comes to fresh potatoes. This accounts for two-thirds of the waste in respect of fresh potatoes from conventional farming. For organic potatoes, this figure rises to three-quarters.

Consumer health protection also leads to waste: producers reject one in three potatoes after harvest because they are rotten or green and could therefore be harmful to health. Wireworms, ie, the larvae of click beetles, have also eaten holes into many potatoes, which are then discarded, although they would still be edible.

New varieties, different habits

In order to reduce potato waste, the researcher suggested taking action on the producer side, by using suitable cultivation methods such as crop rotation to minimise infestation, by protecting plants against wireworms and by breeding new, more robust varieties of potatoes.

Loosening quality standards so that misshapen or scabby potatoes could make it onto the shelves could reduce losses of conventional fresh potatoes by 4% and organic table potatoes by 3%. However, this could merely transfer the waste from the producer to the consumer, who may refuse to consume potatoes that don’t meet their expectations.

Willersinn said the eco-balance is at its worst when consumers throw potatoes in the bin, because by that stage, the most energy has been put into the product. He believes the most sensible thing is therefore to minimise household waste, by educating consumers to change their preferences, buying and eating habits.

Photo: Christian Willersinn/Agroscope/ETH Zurich