Home-scale Biogas for the World

Situations like these are a daily occurrence in the South American 6-million-inhabitant metropolis. Especially the World Cup and the upcoming Olympic Games have intensified the conflict between the Brazilian government and the drug cartels ruling the favelas. In fact, the local residents appreciate some of their government’s more recent concessions like the garbage disposal or public transportation. However, what they appreciate even more is the form of personal independency that they managed to preserve over the years. Simply calling the favelas a slum would not do justice to them. Many inhabitants are social dropouts, artists; others just could not pay their horrendous rents anymore.

For though they are full of crime and trigger-happy policemen, Rio’s favelas provide us with the perfect test site for our purposes and lots of liberty. Collaborating with some locals and Architecture for Humanity we are building home-scale biogas systems. Actually, they are just a smaller version of the plants you may already have seen in the countryside – the principle is the same. Kitchen, food, certain garden waste and black water are dumped into a big, closed tank where methane-producing bacteria will start breaking them down. All you have to do is to collect the gas; it can then be used for cooking, heating and even generating electricity.

The 18 m3 system that we built in Brazil is comparably big. In fact, this is necessary as it belongs to a school which will soon use it to clarify its black water, dispose its bio-waste and use the biogas for cooking. Constructing the home-scale biogas plant is surprisingly easy: A system of steel moulds has to be oiled and then put onto a pre-cast concrete fundament. Additional concrete is poured into the space between the moulds. You remove them after two days have passed – voilà, there is your home-scale biogas plant. All you have to do now is to add a fibreglass dome to contain the gas. And best of all: The moulds can be re-used as much as you want. That way, many plants are constructed at extremely low expenses in a short period of time.

This plant in Rio de Janeiro will be mostly covered by soil

Plus, there are also solutions for private construction in your basement, garden or even on your balcony. This is what I did with a friend of mine in a local yard: Together we put up a 1 m3 system simply consisting of an isolated IBC tank (as you have maybe seen one in the harbour or used as a rain barrel) and three pipes we fit into it: one for the food scraps, one for the high-quality liquid fertiliser also coming out of the system and another one for the biogas we are generating. The plant is working fine – absolutely CO2-neutral, not relying on energy crops or anything for that matter – and inspires us every day with its beautiful flame. Costs: less than 100 €.

There are more pictures available at Niteroi - Brazil 2014

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