The WonderBag – updating the world’s oldest cooking method

When she was a child, her granny would take the pot of porridge from the stove and wrap it in cushions and blankets to finish cooking. That, Sarah Collins realized in 2008, was actually heat-retention cooking, the world’s most ancient way of cooking.

Cooking “pits” show archeologists that an area was inhabited by humans, and many people still use earth ovens today. In 19th century Europe, “hayboxes” were a common slow cooking method which used hay or straw for insulation, and they became popular again during WWII as a way to conserve fuel. In the 1970s, another South African outfit had distributed a similar product called the “wonderbox,” which used bags filled with polystyrene chips.

Working in social change for a decade had taught Sarah that problems such as deforestation and poaching would not change until communities – especially rural grandmothers – had a solid basis for earning a living.


It was during electricity cutbacks in 2008 that forced her to eat out most evenings that she suddenly woke up late in the night and remembered her grandma’s cooking method. “And I realized in that moment,” she says, “that this could be a technology that could change the world.”

Wonderbag is a phenomenal form of womens’ technology that solves all kinds of problems at once – while also saving on electricity or natural gas bills. And not only is it a cheaper way to cook, it is smoke-free and thus healthier for women and children. It also saves on water use, which matters a lot in South Africa. I discovered this invention through a marvellous article in Roads and Kingdoms – From South Africa, A Wonderbag for the Future.

This low-tech slow cooker is a cloth bag stuffed with squishy insulation made from recycled insulation from cars and houses. Women place a hot, half-cooked meal inside the bag, pull it shut, and a few hours later, the food is ready because it finished cooking in the bag’s insulated padding. Little wonder that it’s called Wonderbag.

But it does more than just cook meals. Because women don’t have to use electricity, gas or wood to cook most of the meal, its production can be supported by carbon credits. Annually, each unit saves up to 70% of cooking fuel, reduces indoor air pollution by 60%, diverts 1,000 hours of unpaid labor, saves five large trees from deforestation and up to a ton of carbon emissions per year, and can boost household incomes by $2 per day.

The  WonderBag’s appearance was the result of a serendipitous meeting on an airplane. Sarah met Mandisa Moshy Mathe, founder of Youth for Survival, and, admiring her clothing, learned it was all made in their factory in South Africa. But Moshy explained that because they were an NGO, they never had enough jobs for the women that she had trained in sewing through the project.


It was a marriage of minds. Moshy became a co-founder, making the first WonderBag from the fabric of the dress that Sarah had admired on the plane, and says it has made a huge difference to the women she works with. In one community, it has created 1,000 jobs.

The bags have become popular in South Africa, Rwanda, Kenya, Nigeria, and Somaliland, and they are sold in 27 countries, including the USA (through Amazon).

People want to eat more healthily, says Sarah, and the economy in America is actually forcing people to look at alternative ways of eating and moving away from fast food.

In the Kwa-Zulu, Natal factory, 10,000 Wonderbags are made every month, and 5,000 of them are exported to the United States. Worldwide, 750,000 Wonderbags have been sold, and more than 2,000 jobs have been created. Collins and the team are planning on distributing two million bags across the globe.

Companies including the energy giant Sasol, the fast food chain Nando’s, and the French state-run energy utility EDF have purchased offsets from Wonderbag in recent years. 

In 2011, Unilever CEO Paul Polman invited Sarah to come to Davos.

“I was a farm girl, now here I was presenting to heads of state and companies. The Dutch Prime Minister was presenting at Davos and had a prepared speech that he threw away and asked me to come on stage to talk about the Wonderbag. Because I am so passionate about it and believe it works, it’s been a bit easier to talk in front of groups,” Collins says.

Berkeley recently studied the economic benefit of the Wonderbag program. “Wonderbag shows that you can attack these social causes with models that are economically viable,” says Polman.  “Sixty percent of our business is now in these emerging markets.  We’re dealing with the bottom 2.5 billion on the planet, many of whom have no access to water or hygiene or all the issues around food security, with a billion people going to bed hungry.  We cannot reach them alone.”

The Wonderbag is a nominee for the 2022 Food Planet Prize.

In 2022, over 2,500 Wonderbags were donated to two NGO’s in Ukraine that are supporting families. The Wonderbags, sent from the UK warehouse, were distributed to families fleeing from war-torn areas such as Mariupol, as well as families remaining in Ukraine who had limited access to gas and electric for cooking. 

Cover image: WonderBag