As the sun sets over the streets of Copenhagen, Matt Homewood switches on his headlamp and prepares to climb into another bin.

A few minutes later he resurfaces with his haul: a dozen Uruguayan steaks, grown 11,980km away across the Atlantic and dumped unceremoniously in an alley behind a supermarket. 

Every year, Denmark's supermarkets throw away 96 million kilograms of food. Homewood, an environmental activist, has made it his mission to document the waste. 

One night, he finds a shipment of Chilean blueberries. Another day, 153kg of dairy cream. In August, he discovered an astonishing $1,130 (£840) of cheese, all discarded as rubbish.

"Waste on this scale is near-unfathomable," says Homewood. Most of the food he collects is still perfectly edible. Meanwhile, 251,000 Danes live in poverty.

It is a problem around the world. At least 2.5 trillion kilograms of food goes uneaten every year. Rich countries are some of the worst offenders. 

At the same time, one in every eleven people is suffering from severe food insecurityPeople suffering from severe food insecurity lack sufficient food to grow, develop and lead a healthy life. . The pandemic has exacerbated the issue: during lockdown, 1.5 million Britons went entire days without eating. 

This is not just a humanitarian disaster, say activists, but a climate disaster too. If food waste was a country, it would be the third highest greenhouse gasGases in the Earth's atmosphere that trap heat, contributing to global warming. Carbon dioxide, methane, nitrous oxide and water vapour are all greenhouse gases. emitter after China and the USA. Valuable farmlandAgriculture now uses nearly half of the ice-free land on Earth, threatening many animal species with habitat loss and extinction. Cutting down on waste could cut down on the land needed to grow food.  and polluting pesticides are used to grow food that never reaches a kitchen table. 

So why do supermarkets throw so much food away? 

There is no doubt: supermarkets have provided shoppers with more choice, more convenience and cheaper prices than ever before. But the tactics used to lure customers away from rivals can also lead to huge waste.

In 2012, one American study found that shops deliberately overstock products under the assumption that people are more likely to buy from a fully stocked display.

Some foods fall victim to excessively cautious labelling - one yoghurt manufacturer proved their yoghurts were still edible 45 days after the use-by date.

And other foods never even make it onto the shelves. In France, potatoes less than 25mm and more than 70mm are rejected as "ugly" and unsellable.  

Some stores are responding. As Cop26Cop stands for  Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change got underway in Glasgow, five major UK supermarkets promised to halve the environmental impact of a weekly food shop by 2030.

But campaigners say voluntary actions do not go far enough. Instead, they want the law to change. In France, supermarkets can already be fined for refusing to give away unsold food.

Homewood is calling for a tax on food waste. In Denmark, food banks recover only 1.8% of dumped foods. 

Homewood believes that a tax would compel supermarkets to invest in innovative new technologies that could streamline their operations, from an AI pricing systemA pilot of an Artificial Intelligence pricing system that reduces the price of a product as it gets closer to its use-by date reduced overall waste by a third at a Spanish supermarket.  to plant-based packaging that prolongs shelf life. Until then, he will keep reaching into the bins. 

Yes, say some. It is extraordinary that shops are allowed to throw away so much food without any consequences while millions go hungry. We cannot wait for supermarket bosses to make changes on their own. A tax would force companies to reconsider their wasteful ways. 

No, say others. Taxes would not solve the global supply chain problem. It would simply encourage supermarkets to raise prices on other goods. This would harm the very people the tax is trying to help - those who are living in poverty. And the blame cannot be on supermarkets alone. Plenty of food is thrown away in homes too.