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These Hilarious Inflated Backpacks Are Actually Delivering Cheap Local Energy To The Rural Poor

The idea could allow villagers to invest in expensive machines that turn manure into energy–and share the results.

Millions of rural villagers around the world still cook with wood and charcoal, with all the limitations and inconveniences that implies. Women spend time and energy collecting and hauling wood, which contributes to deforestation and takes them away from more productive uses of their time. Worse, burning wood and charcoal inside homes produces extremely unhealthy fumes.

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Biogas produced from organic waste, such as cow dung and farm cuttings is a good alternative, because it’s lightweight and clean burning. But it’s not possible to have a bio-digester–a system for breaking down the waste to produce biogas–in every person’s home. That’s too expensive and impractical. You need upwards of five or six households invested in a digester to cover its costs.


Katrin Puetz saw the potential of biogas for rural communities while doing her master’s thesis at a university in Germany. She wondered how to do the “last mile” of distribution from a central digester site to someone’s home. She came up with the biogas “backpack”–a sturdy bag to transport the gas.

Since then, she’s created a full line of products for villages to use biogas locally. First there’s a 2 x 5 meter bio-digester “system” for 44 pounds of cow dung a day. It’s a tank with an outer tent covering. Then, there are the packs which hold 1.2 cubic meters of biogas at a time (6 kilowatt-hours of energy or enough for four hours of cooking). And there’s a simple stove and several other parts.

The bag has a valve that attaches to the stove with a hose. Villagers place a rock or plank of wood on top of the bag to push the gas out. The bag presents no explosion risk because it is isn’t pressurized, Puetz says. “You can put the bag on an open fire and it will take 15 to 20 seconds to even melt the material. It is a very heavy duty material. And even after you’ve melted a hole the gas will come out and slowly flare off, because biogas needs to be mixed with air to be flammable,” she assures us.


Puetz recently spent a year in Ethiopia piloting the system with a local organization. She became convinced that a model of biogas clusters could be a viable business–and, importantly, without any outside help. Puetz advocates subsidy-free development based around local people cooperating and sharing resources (she’s turned down several opportunities from grant-making entities). Hers is a social business. She sees one person setting up a digester, having too much gas, and covering their costs by selling to others.

Returning to Germany last summer, Puetz set up B Energy and worked on the business model (which is to franchise technology and service it). B Energy now has franchisees in Ethiopia (where Puetz is now based) and Chile. The first two partners are both women who have built their own small businesses around producing and selling the gas.

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To help villages calculate their “biogas potential,” Puetz has a calculator at her site. You just need to enter how many cows you have and other available substrates (e.g. cuttings). It estimates the size of digester needed, and the amount of gas you can produce.

The full systems cost about $600, but that doesn’t include shipping or installation. At the moment, Puetz is funding everything from her savings. She just turned down a $500,000 bank loan because she felt like it would be giving up control. She’s open to investment, but only if partners expect no equity and are happy to forgo interest. Puetz wants to create an equitable business, where nobody makes excess profits but everyone benefits from using cleaner, less damaging fuel.

About the author

Ben Schiller is a New York staff writer for Fast Company. Previously, he edited a European management magazine and was a reporter in San Francisco, Prague, and Brussels.

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