Every Sunday at 2 p.m., Marisela Godinez, the owner of El Mesn Tequilera, a Mexican restaurant in Austin, Texas, used to fill a 12-gallon bucket with leftovers from the restaurant. A lot of food was thrown out.

A few months ago, Ms. Godinez signed up to use an app. She sends less scraps to the landfill or compost now that she has 10 customers who pick up surprise bags of her leftovers for $5.99 each.

There are apps that connect customers to businesses that have leftover food. Huge amounts of food are thrown away by restaurants and grocery stores. Too Good To Go and flashfood help businesses sell it at a reduced price rather than throwing it away. They claim that the businesses and buyers are helping the environment because the food would otherwise be thrown away.

The apps that make money by taking a portion of each sale use language that sounds more like a call to arms than a grocery list. The description says to fight against food waste. Users of Too Good To Go are referred to as food waste warriors.

Around the world, similar apps are being created. Treatsure started selling leftovers from hotel buffets in Singapore. There are bakeries, coffee shops and grab-and-go restaurants in Hong Kong. Tabete is like a model in Japan.

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Between a quarter and a third of global emissions come from the food production industry. The process of growing, harvesting, moving, processing, packaging, storing and preparing food releases greenhouse gasses. All those emissions are related to the food being wasted.

Methane is released when unused food reaches landfills.

Emily Broad Leib is the Director of the Harvard Food Law and Policy Clinic. It can be expensive for businesses to store, transport and donate it. She thinks that the apps make it easier for businesses to do their jobs.

More than 1,400 supermarkets in the United States and Canada now work with flashfood, which was launched in Toronto about half a decade ago. There is a Stop & Shop store in the Bronx. Retailers can use the flashfood system to sell food at a reduced price when it's nearing the end of its shelf life. Customers can purchase items through the app and pick them up at a store. The food takes a cut.

ImageA close photo of a box of bright red apples in a cardboard box, with Ms. Wash's hands reaching into the box.
Produce from a Meijer store near Jody and Jerry Wash’s home in Hammond, Ind.Credit...Lawrence Agyei for The New York Times
A close photo of a box of bright red apples in a cardboard box, with Ms. Wash's hands reaching into the box.
ImageA portrait of Jerry and Jody Wash smiling and sitting side-by-side on an off-white couch wearing blue shirts, in front of a white-and-tan curtain decorated in a circular pattern.
Mr. and Ms. Wash. “Most people are checking their social media,” he said. “We’re checking Flashfood.”Credit...Lawrence Agyei for The New York Times
A portrait of Jerry and Jody Wash smiling and sitting side-by-side on an off-white couch wearing blue shirts, in front of a white-and-tan curtain decorated in a circular pattern.

JerryWash, a retired railroad ticket agent, said he looked to see what was available at his local store. Most people check their social media in the morning. We are looking at flash food.

Mr. Wash and his wife, Jody, didn't shop at the regular clearance sections of grocery stores because they were "bruised" and "bad." He said that they've been planning meals around what's available on the app.

The company's founder and chief executive acknowledged that he had recreated the clearance rack on people's phones, but he said the presentation was key. He said that the food in the back corner made him feel smaller. There are blue fridges in the front of grocery stores with signs that encourage people to fight food waste.

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Too Good To Go is trying to get people to buy leftovers. In the United States, customers in 12 cities can browse restaurants and stores, then reserve surprise bags that typically cost about $4 to $6 and contain food that would have been originally priced at around three times that amount. It is possible to pick up the bags at a certain time. Too Good To Go charges partners an annual fee.

The app was heard about by a tax analyst. A friend of mine posted a picture of their food that they got from Too Good To Go and they got a bunch of ribs. I want a lot of ribs. I agreed to it.

It feels like an adult trick-or-treating. Seven soggy tortillas, a chicken sandwich, two dozen extra large sausage kolaches, and seven separate orders of cupcakes, cinnamon rolls, cookies, and croissants are among the highlights from the 76 bags she has ordered.

The company's co- founder said consumers really enjoy it. There is a community of over 10,000 people sharing photos of bags on the internet.

Others post on Facebook. Kate Mytron posted a picture of four slices of pizza with the caption, "Not the best pizza, but well worth the $5." There is a bag of rotten produce in New York. He said there wasn't anything usable in it. It all ended up in the trash.

Mr. St. Germain said he had stopped using the app because of bad orders. He was gaining weight from eating too much food.

ImageA close-up of a tablet at a desk, held by a person whose right index finger scrolls through images of food on its screen.
Too Good To Go on a tablet in Berlin. The app is popular in Europe.Credit...Markus Schreiber/Associated Press
A close-up of a tablet at a desk, held by a person whose right index finger scrolls through images of food on its screen.

Too Good To Go is more popular in Europe where it operates in 15 countries. The company said it was expanding in the US and was currently testing partnerships with Safeway and Panera.

Food waste experts are positive that these types of apps can help limit the amount of food sent to landfills. Lorenzo Macaluso, the chief growth officer at the Center for Eco Technology, said that there is space for all of these solutions to coexist. There's a lot of food waste out there.

Mr. Macaluso said that food banks are usually set up to handle much larger donations than these apps. He said that those kinds of apps fill a unique niche.

The apps have the ability to reach people who are in need of sustenance. According to its own survey data, one in five shoppers at flashfood experience food insufficiency, and the company is trying to allow government assistance cards as payment methods. Too Good To Go didn't accept food stamps and didn't have the same information as users, according to a spokeswoman.

At least a few items for sale on Too Good To Go aren't necessarily what buyers think of as "food waste." The owner of a Baltimore dessert shop thought the app was a promotional tool to reach new customers. A beverage company owner uses the app to sell discontinued products, but also sells new flavors in hopes of getting new customers.

The Too Good To Go director said the app deterred this type of behavior. He said that if someone is paying $5, they should be getting fifteen dollars of food. It isn't a profit- generating platform. When businesses misuse the platform, it ends the partnership, he said.

Professor Broad Leib thinks that these apps will make users reconsider their own food waste. Making people more aware of the issues is the best way to change consumer behavior.

Ms. Rexrode is a tax analyst in Austin who uses Too Good To Go. The app shows how much carbon dioxide she has saved based on the number of bags she has purchased.

She pointed out that the number may not be accurate. Ms. Rexrode said that they don't know how much she has contributed. I am in the car.