Editor's Note: Tristram Stuart is one of National Geographic's 2014 Emerging Explorers , part of a program that honors tomorrow's visionaries—those making discoveries, making a difference, and inspiring people to care about the planet.

Tristram Stuart thinks we should do something revolutionary with food: Eat it.

The British author calls the problem of food waste "scandalous and grotesque" and cites statistics to prove it:

The planet's one billion hungry people could be lifted out of malnourishment with less than a quarter of the food wasted in the United States, United Kingdom, and Europe.

The water used to irrigate food that ends up being thrown away could meet the domestic water needs of nine billion people.

Until a few years ago, the colossal scale of food waste was largely unaddressed. But Stuart's 2009 book, Waste: Uncovering the Global Food Scandal, and the grassroots initiatives he launched have lifted the topic from obscurity to prominence worldwide.

"We want to catalyze a food-waste revolution one person, one town, one country at a time—helping stop needless hunger and environmental destruction across our planet," he says.

Stuart's passion started with pigs. At age 15, he raised a few pigs to earn extra money, feeding them with leftover food from his school kitchen and local shops. He soon realized that most of the food that went to the pigs was actually fit for human consumption. He also began noticing supermarket garbage bins overflowing with fresh food.

View Images As a teen, Tristram Stuart raised pigs. He fed them leftovers from local shops and was shocked by how much food was going to waste. Photograph by Kat Keene Hogue, National Geographic Creative

"Everywhere I looked, we were hemorrhaging food," he says. "So I began confronting businesses about the waste and exposing it to the public."

His research revealed that most rich countries produce between three and four times more food than required to meet their citizens' nutritional needs. Yet one billion people suffer from malnutrition worldwide.

"Producing this huge surplus leads to deforestation, depleted water supplies, massive fossil fuel consumption, and biodiversity loss," Stuart says. "Excess food decomposing in landfills accounts for 10 percent of greenhouse gas emissions by wealthy nations."

In 2009, Stuart launched what has become the flagship event of his global food-waste campaign: Feeding the 5000. Created entirely of food that would otherwise be wasted, the free feast in London has been replicated around the world.

"These events give people a clear, tangible idea of food-waste problems and potential solutions right where they live," Stuart says. "A few years ago most big U.K. supermarkets wouldn't even talk to food redistribution charities—today they all do."

Stuart has also successfully campaigned for retailers to relax strict cosmetic standards for fruit and vegetables. "Farmers leave up to 40 percent of harvests rotting in fields because their produce doesn't conform to the perfect size or shape big supermarkets demand," Stuart says. "This even happens in countries like Kenya where millions of people are hungry."

Since Stuart's efforts began, many supermarkets have changed policies. "Ugly" fruits and vegetables are now the fastest growing sector in the fresh produce market. Since stores can sell them for less, shoppers get a bargain. In 2013, U.K. farmers sold 300,000 tons of produce that would once have been rejected, an increase of 20 percent for many growers.

View Images Food waste “leads to deforestation, depleted water supplies, massive fossil fuel consumption, and biodiversity loss," Stuart says. Photograph by Kat Keene Hogue, National Geographic Creative

Farmers have benefited from Stuart's actions in other ways as well. Previously, if supermarkets cut back on their produce order at the last moment, farmers bore the cost. After Stuart and other organizations spotlighted the problem, legislation was passed to force U.K. retailers to share the burden. "Now [supermarkets] have an incentive to improve forecasts and hence curb waste," says Stuart.

Even so, some produce is still left in fields to rot. Stuart's Gleaning Network sends thousands of volunteers to harvest that surplus food, which is then distributed to the hungry. The network has expanded across the U.K. and France, and will soon launch in the Netherlands, Belgium, and Germany.

Stuart has not forgotten his porcine roots. Another project, The Pig Idea, seeks to change laws that restrict using food waste to feed pigs. "Pigs were originally domesticated for the sole purpose of recycling human food waste back into food," says Stuart, "a process that has worked for thousands of years."

These days, many countries "import millions of tons of soy from South America to feed pigs—causing massive deforestation throughout the Amazon," he says. "We also feed pigs wheat and maize, which hungry people in Africa and Asia could eat."

His initiative calls for a strongly regulated system that would allow pigs to be safely fed food waste once again. The campaign has inspired supermarkets to send waste that is legal for livestock, such as bread, to farms rather than landfills. "Feeding food waste to pigs saves 20 times more carbon than the next-best recycling method," he says.

Stuart works with a small team in London, devising and testing ideas, then sharing them with anyone who can replicate and expand them worldwide. "We've become an international hub for sharing knowledge, communicating best practices, and forging collaborations," he says. "The food-waste movement started as a trickle—but today it's a tidal wave."

He stresses that each individual can make a powerful difference: "In the U.K., food waste in homes has already decreased 25 percent.

"Citizens are the sleeping giant in this equation," adds Stuart. "By rising up and speaking out, we can—and are—making the world's food system less unjust and more sustainable every day."