It's around 6 o'clock on a Sunday evening, and Anne-Charlotte Mornington is running around the food market in London's super-hip Camden neighborhood with a rolling suitcase and a giant tarp bag filled with empty tupperware boxes. She's going around from stall to stalll, asking for leftovers.

Mornington works for the food-sharing app . "If ever you have anything that you can't sell tomorrow but it's still edible," she explains to the vendors, "I'll take it and make sure that it's eaten."

Olio wants to make it easy for busy food sellers to avoid wasting food. "These vendors usually don't have enough surplus to donate to a charity or something, but they still end up having to throw away quite a lot at the end of the day," Mornington explains. "So either I or some volunteers will come everyday to collect any scraps and put it on the app."

In fact, anybody in London with a smartphone — be it a restaurant, grocer or just a regular Joe — can upload pictures of their leftover lunches and dinners, spare ingredients or unwanted produce onto the app. Those hankering for a free meal can then peruse the offerings, message those who've got food to spare and then go collect it — for free.

Olio is just one of many start-ups and small enterprises working to reduce food waste in London. When researchers at Trinity College Dublin recently launched a database identifying more than 4,000 food-sharing and waste-reducing enterprises in 100 cities around the world, they found that London — with 198 such enterprises — had more than any other city.

"We decided to focus on cities, because more than half of the world's population now lives in cities," explains Anna Davies, a professor of geography and environment at Trinity who led the research. City dwellers produce more than a billion tons of solid waste annually — and about half of that is food waste. But cities are also centers of innovation, Davies says. "So we were curious — what difference is technology making to the way we share food in cities?"

Quite a lot, it turns out.

Over the past three years, technology has transformed the way Londoners are approaching food waste, says Laura Hopper, the CEO of Plan Zheroes, a social network that connects charities that need food with local businesses that have a surplus. "We have so many organizations in London doing good work."

Initially, the idea for Plan Zheroes came from Lottie Henley, a nonagenarian whose experiences as a refugee during World War II motivated her to do something about food poverty in London. Back in 2011, through a city-wide program designed to encourage green entrepreneurship, Henley got some seed money and teamed up with some techie types to design Plan Zheroes.

Now restaurants, coffee shops and small grocers that have just a little bit extra can use the platform to find nearby homeless shelters and food banks in need. The organization also recruits a small army of volunteers who help run food between the businesses and the charities.

"This isn't a large-scale thing. It"s really about helping communities connect," Hopper says. "Plan Zheroes fills a very specific niche."

Several other London-based enterprises do the same — they aim to reduce food waste in one or two small, specific ways. London-based startup makes snacks out of produce that would otherwise be wasted, and , turns waste from London's wholesale markets into smoothies and juices. A company called uses surplus fruit and veg to make relishes, and another called uses vegetables that are past their prime to make hummus.

Then there's — a sort of Blue Apron for seafood — which helps both consumers and fishermen avoid waste by allowing the former to specify online exactly how much they need so that the latter can deliver exactly that, no more and no less. And is an online catering service that will bring boxes of day-old donuts, pastries and other baked goods straight to your office — and the proceeds all go to charities that tackle child hunger.

"Of course, technology alone isn't enough to build a sustainable food-sharing community," says Davies from Trinity College. "The social connections are important — but what technology can do is help people make those connections."

Back at London's Camden market, Anne-Charlotte Mornington from Olio has collected over 30 portions of food. Anna Kidd, who works as a volunteer with Olio, has joined Mornington in the task of cataloguing and photographing all the nosh: several servings of fragrant, spiced rice from an Indian food stall, Thai chicken curry, a chicken masala wrap and a bag full of hot dogs.

It'll all be gone within a day or two, as hungry Londoners come to collect it all. About 85,000 Londoners interested in either donating or collecting surplus food have made accounts on Olio so far.

"It feels so good that we've saved all of this from going in the bin," says Kidd, who herself uses the app to pick up odds and ends for her pantry.

"I don't think I've bought any spices since I've got the app," Kidd says. "It's amazing." Plus, Olio has an added benefit, she says. "You get to meet people and have conversations when you pick up the food. I've really gotten to know my area better."

Maanvi Singh is a writer based in London.

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