The innovation turning human waste into a powerful stink-free resource


This story is part of an Ashoka series in collaboration with Salt, spotlighting leading young innovators to support the Unilever Sustainable Living Young Entrepreneurs Awards, a global competition launched by Unilever in partnership with Cambridge Institute for Sustainability Leadership. To follow the conversation on Twitter, search #GlobalGoals for a #BrightFuture.

What is waste worth? For more and more families across Latin America, it’s worth a whole lot.

“We’re converting the grossest thing—poop, basically—into something beautiful,” Alex Eaton said. He’s the founder of Sistema Biobolsa, a social enterprise that manufactures and distributes biodigesters to rural (often indigenous) groups in Mexico and nine other countries.


Biodigesters? To oversimplify things: They’re large, durable membrane bags that are installed in a trench. Biodigesters accept deposits of waste from pigs, cows and, yes, even humans in one end, which are broken down inside the system by “good bacteria.” On the other end, farmers score energy in the form of methane-rich biogas and organic fertiliser. The biogas burns bright blue and can be used to power boilers, stoves, motors, and generators, while the organic fertiliser nourishes a farmer’s land better than any chemical fertiliser could, leading to harvests with stronger nutritional profiles.

“The transformation can be seen through a loop,” Eaton said. “We grow the plant that feeds the cow that poops it out again and that goes back into the biodigester.”

A farming family with four pigs can produce enough biogas to power their kitchen. The fertiliser produced by their $500 biodigester can be applied to the rows of grains and beans in their backyard milpa, which feeds the family. Farmers often see a 20-40 percent increase in crop yields in the first year, which only improves with each annual harvest. On a farm with 1,000 pigs, a family equipped with a $20,000 system can produce more energy than they can consume and even sell power back to the Mexican electrical grid.

A biodigester is an investment of a lifetime but not because of the cost. Eaton, raised in a small farm in rural New Hampshire, rare in the United States, found kindred spirits in Latin American smallholders. Eaton said his work has always been about quality and value. The first biodigester he installed in 2007, just a prototype, is still humming—and should keep humming for another 20-some years with adequate maintenance. Sistema Biobolsa has also partnered with Kiva to offer interest-free loans to afford their systems, which farmers pay back with the very same benefits they generate.

Positive impacts

The positive impacts are realised by the planet as much as by people. The livestock business generates more greenhouse gas emissions than transport, as measured in carbon dioxide equivalent, according to the Food and Agriculture Organisation of the United Nations. The sector also pollutes water sources with runoff from animal waste, antibiotics, hormones, chemical fertilisers, and pesticides that are used on crops.

Sistema Biobolsa transforms methane gas and carbon dioxide into renewable energy, capping the greenhouse gases released by farming activities, and the use of organic fertiliser prevents watershed contamination. And because farmers adopt biogas as a power source for their homes, they neither depend on fossil fuels nor cut down trees for fuel, which protects them from indoor air pollution and slows deforestation.

The biodigesters, in this way, becomes more than just bags for rural families. Eaton said they also trigger an emotional relationship to the world around them and farmers begin to buy into a waste-to-reuse culture.

“Waste is a construct that we’ve invented as humans. In an ecosystem there wouldn’t be any waste. The output from one things would be an input for another. It’s all basically captured sunlight,” Eaton said. “This deep understanding is really a breakthrough for farmers. And they start seeking that out in other areas of their lives.”


It’s almost unprecedented. The time savings and cost savings allow farmers a taste of simple luxuries to be enjoyed month after month for the rest of their lives. “Women begin to get together to make yogurt, or cheese, when they used to sell raw milk. They’ll process some of their vegetables and use it for canning. Families are able to take extra hot showers,” Eaton said. “It’s empowering.”

The Sistema Biobolsa team has installed more than 2,600 biodigesters across Latin America, spreading mostly through positive word-of-mouth reviews, but serious scale is on the horizon. “It’s not a sexy subject matter, but it’s awkwardly appealing, so we’re hopeful that a new round of diverse, pro-active marketing will appeal to more people.”

Sistema Biobolsa also sees the carbon market, which has been active in Mexico since 2005, as a mechanism to accelerate adoption. The social enterprise will serve as an aggregator for its network, making carbon credits commercially viable and available for purchase by countries looking to offset some portion of their own greenhouse gas emissions.

“We reduce greenhouse gas emissions in a number of different ways, both from waste and by displacing fossil fuels. A global price for carbon would be a huge boon to our work and would allow us to lower the price of our technology to farmers,” Eaton said.

He expects to announce Sistema Biobolsa’s first carbon credit sale later this year.

“Change won’t happen fast, but we’ve been a clear and consistent voice in this movement for 10 years and prove the value of our work,” Eaton said. “We’re a total social business, in it for the long-term.”

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Photo Credit: Paul from Flickr

This article was originally published on Virgin Unite.