(CNN) Our interview with Adam Smith is interrupted by a raid from environmental health inspectors.

Smith recently opened the UK's first waste food supermarket, a vast facility in the northern city of Leeds stacked with tons of intercepted produce. The launch attracted huge donations, hordes of shoppers, and interest from government agents.

"They could have shut us down quite easily," says Smith after the inspectors leave. "But there were 500 people in the warehouse, including families and kids, with shopping trollies full of food."

"I told them 'you are going to have to work with us because otherwise all this food is going to landfill, and I'm going to tell people you are allowing it.'"

Clashing with the authorities is routine for Smith, a chef turned waste food entrepreneur who has defied the law in building a global network of cafes that serve meals rescued from back alleys and trash cans.

The Real Junk Food Project (RJFP) has launched over 120 eateries in seven countries from Israel to Australia, and the movement is gathering pace.

The UK's first waste food supermarket recently opened in the northern city of Leeds.

Building the network

In 2013, Smith returned from a spell of traveling abroad and became increasingly frustrated at the scale and impact of food waste.

That same year, a wide-ranging report found that up to half of all the food produced globally -- around two billion tons -- goes to waste , taking a heavy toll on water consumption and carbon emissions.

More Champions for Change For more about inspiring people and causes, including how CNN anchors and correspondents are getting involved, go to CNN.com/Champions.

The young chef resolved to make a difference, and began by opening a small cafe in his hometown Leeds. He used produce recovered from supermarket bins, and charged customers on a "pay as you feel" basis.

The cafe rapidly gained popularity and word traveled fast. Several more sprang up in Leeds using the same model, and Smith started taking calls from abroad.

"People from all over the world got in touch to say 'can we have one in our town?'" he recalls. "We shared our model like an open source concept and said how we did it. Next minute people were calling themselves the Real Junk Food Project in South Korea, Israel and South Africa... It just exploded."

Outside the Armley Junk-tion in Leeds - the first Real Junk Food cafe, launched in 2013.

Ground force

Despite the rapid expansion of the RJFP, Leeds remains the heart of the empire with 14 "pay as you feel" cafes.

Smith employs 30 full-time staff, with many engaged in interception missions from businesses across the city. The project has supply deals with supermarkets and looser arrangements with restaurants and food banks.

The interceptions deliver a selection of goods that goes far beyond the basics, which allows cafes to serve up even haute cuisine.

Photos: From trashcans to tables Photos: From trashcans to tables Pay as you feel – The Real Junk Food Project is a network of cafes and shops that sell 'waste' food recovered from supermarkets and restaurants, letting customers pay as much as they like. Hide Caption 1 of 9 Photos: From trashcans to tables Help yourself – The UK's first waste food supermarket in the northern city of Leeds, recently established on a "pay as you feel basis" by the Real Junk Food Project (RJFP). Hide Caption 2 of 9 Photos: From trashcans to tables Headquarters – The RJFP was launched in 2013 by chef Adam Smith, beginning with the 'Armley Junk-tion' cafe in Leeds, serving meals using ingredients recovered from supermarket trash cans. Hide Caption 3 of 9 Photos: From trashcans to tables Fuel for schools – The project also runs a program to distribute food to schools in the Leeds area, and currently serves around 12,000 kids. Hide Caption 4 of 9 Photos: From trashcans to tables Haute cuisine – The RJFP sources waste food from supermarkets, restaurants, food banks and other businesses, which delivers a wide range range of delicacies including lobster and caviar, and allows the cafes to serve fine dining. Hide Caption 5 of 9 Photos: From trashcans to tables Systemic problem – Smith is pleased with the progress of his project, but angry with the practices of the food industry and supermarkets, which he believes are designing waste into the system. Hide Caption 6 of 9 Photos: From trashcans to tables Fought the law – The RJFP serves food past its use-by-date as activists believe the dates are misleading and damaging as they encourage consumers discard safe, edible food.

"We have fed half a million people across the world with expired food," says Smith. "I don't know how much more we have to do to prove it is safe."



Hide Caption 7 of 9 Photos: From trashcans to tables Future plans – The Real Junk Food Project has now expanded into an international network, with over 120 cafes in seven countries from Israel to Australia. Smith estimates it has served over half a million people. Hide Caption 8 of 9 Photos: From trashcans to tables Urgent imperative – Food production is the most damaging industry to the environment, taking a heavy toll on water consumption, deforestation, carbon emission, and species extinction. An estimated two billion tonnes of food is wasted each year. Hide Caption 9 of 9

"We get everything from caviar and lobster to fruit and vegetables," says Smith. "The majority of dishes on our menus are chicken infused as we get 150 kilos of chicken a week."

The Leeds team recover around 10 tons a day, but the hauls are increasing. The day before the raid, 75 tons of food arrived at the warehouse.

Healthy platter at the Armley Junk-tion

Smith has had to innovate to manage such volumes. The Project launched a scheme to provide local schools and now serves recovered food to 12,000 kids in the area. The waste food supermarket, also operating on a "pay as you feel basis," is the latest effort to keep pace with the growing supply.

The founder is aware that the campaign touches on wider issues such as poverty and malnutrition that are depressingly common in his hometown, but he is determined to maintain a tight focus.

"We're not here to stop hunger, we're here to stop food going to waste," says Smith. "I truly believe the environmental aspect is what we should be looking at first."

But he adds: "In my eyes, it's a human right that everyone on this planet should have access to food."

The Project now supplies 12,000 schoolchildren in the Leeds area.

'Waste racket'

While Smith is proud of the progress of the RFJP, he sees it as evidence of a deeply flawed and corrupted industry.

He believes supermarkets are the primary culprits for the glut of waste food, and says an employee of one major chain has told him that a large waste allowance is built into their business model.

This practice is denied by supermarkets, but corroborated by other food waste campaigners.

"There is food in supermarkets being used almost like Christmas decorations, rather than intended to be consumed," says Tristram Stuart, founder of Feedback and author of Waste: Uncovering the Global Food Scandal.

While official figures state that consumers are the largest source of waste -- around seven million of the 15 million tons of food lost in the UK each year -- Smith is not convinced.

"There is a racket in this country called hidden waste," he says. "The surplus costs so much for supermarkets to dispose of that it just gets placed in warehouses and shipping containers. Hopefully, this will be exposed soon and the figures will change dramatically."

The team deal with vast quantities of discarded bread each day.

Safe to eat?

Smith also holds supermarkets accountable for waste at either end of the supply chain -- from rejecting the produce of farmers for cosmetic reasons, to conditioning consumers to fear "best before" dates so that they discard vast quantities of safe, edible food.

The RJFP is proud to serve meals with ingredients that have passed their expiry date -- "(We) use our own judgment on whether we believe the food is fit for human consumption," their website announces -- although this has resulted in raids and controversy.

Smith says he is willing to face the consequences to prove his point.

"We have fed half a million people across the world with expired food," he says. "I don't know how much more we have to do to prove it is safe."

Change at the top

The British Retail Consortium (BRC) claims that supermarkets are scapegoats for larger problems elsewhere.

"The level of waste in supermarkets is a minor part of the whole food waste issue," says Andrew Opie of the BRC. "The bigger target is cutting food waste at home, which supermarkets can help with, but we all have the opportunity to do that as consumers."

Opie adds that retailers have sought to reclassify expiry dates to enable longer lifespans, but stresses the health risks of eating food after its use-by-date, particularly for consumers with weak immune systems.

The major supermarkets have also signed a commitment to cut waste by 20% by 2025, although there are concerns over a lack of transparency in reported waste figures, as they are reported for the industry rather than individual supermarkets.

"Mandatory waste audits would be very important for showing which supermarkets are doing a good job and which are doing nothing," says MP Kerry McCarthy, who tabled two food waste bills in parliament, which were rejected. "Some people don't want to show how much is wasted."

McCarthy has also proposed a new law modeled on French legislation that would force supermarkets to give surplus food to charities and distributors, as well as a "Good Samaritan Act" that would protect donors from being sued in food poisoning cases.

New laws could prevent supermarkets from dumping surplus food.

The way forward

Smith has little faith that the industry will reform itself, but he is confident that pressure from below can make an impact.

Hundreds more cafes are planned, including several in the US, and further "pay as you feel" supermarkets will be launched across the UK. The Project is to introduce a new social franchise model that will establish a global code of practice and establish greater unity across the network.

The movement is also joining forces with other food waste activist groups to build pressure on the industry.

For all the progress that has been achieved to date, Smith is aiming for a truly transformational impact.

"We will give people access to food until it becomes a human right to have food," he says. "We won't stop until we do that."