Powerless Cooking With Wonderbag Slow Cooker

Before the days of electric slow cookers, ovens, and stoves, there was fireplace cooking and hay boxes. When they couldn't plug in a slow cooker and keep their food simmering for hours, home cooks simply lined a box with hay, popped a boiling pot of stew into it, covered it, and let it cook in its own heat for hours. It's the Crock-Pot's grandmother, who never quite got Twitter.

Heat-retention cooking goes far beyond the hay box, however. Classic clambakes cook with heat retention: Put rocks on a fire, layer seaweed, seafood, more seaweed, and a tarp, and let bake for about a half-hour. The solar oven, which captures heat from sunlight, then retains it in its well-insulated boxes.

And now? The Wonderbag has hit the U.S. market. Essentially a well-insulated bag, the cushion is filled with recycled insulation, sown up in patterned prints by Moshy Mathe, and distributed as replacement, no-energy slow cookers. "I grew up on a farm where we didn't have electricity so my grandmother, she used to make stock and she'd take it off the stove and just wrap it and wrap it in blankets, and just leave it," founder Sarah Collins said.

Then in 2008, Collins' home in South Africa went with spotty electricity for four months. "We'd have it sporadically like twice a week, and I was thinking, this is ridiculous," she said. "One night, I woke up in the middle of the night and I remembered my grandmother, and I thought, 'Why isn't anyone doing heat-retention cooking?'"

Anecdotal evidence aside, heat-retention cooking does work, and science backs it up. Food must be at a temperature of more than 60 degrees Celsius (140 degrees Fahrenheit) to be considered safe; the Wonderbag has been tested to keep 4 liters of water above 65 degrees Celsius for more than six hours. For the first four hours, if left untouched, a stew can be kept between 87 to 93 degrees Celsius (188 to almost 200 degrees Fahrenheit).

So bring a pot of vegetables, beans, and meat up to a boil, wrap the pot in the Wonderbag, seal it for five hours, and you'll have chili without plugging anything in. Transport hot stews and casseroles without worrying about reheating them at your destination. And even reserve a bag for cold items (like ice cream) to keep frozen foods from melting on your way home.

It's deceptively simple. "People in the beginning are like, we don't believe this," Collins said. "But we've been through every test, labs, and once you start to get used to the way it works, you can cook brilliantly in the Wonderbag because of the efficiency."

Part of the efficiency is, of course, reducing the amount gas, electricity, and water that go into everyday cooking. A Wonderbag can reduce a family's fuel usage by up to 30 percent (and fuel is getting expensive), and their carbon dioxide emissions. Collins suggests halving the amount of water used in recipes for the Wonderbag, as less water is evaporated during the cooking process thanks to the insulation. And every time a consumer buys one online on Amazon, another bag is donated to a family in need in Africa.

"It's the Toms shoes of food," Collins said. "The point is the world needs it; we are running out of fuel." And even though 600,000 Wonderbags are already in use, Collins is aiming for 100 million Wonderbags by 2015. No big deal, just making the world more eco-friendly, one bag at a time.