What are biodigesters?

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They are relatively simple manufacturing equipment, which makes it possible to reuse waste to generate gas and fertilizer, also called biogas and biofertilizers. The biodigester is generally fed with food waste and animal feces, plus water.

Inside the device, these wastes are decomposed by the action of anaerobic bacteria (which do not depend on oxygen). During the process, all the organic material ends up being converted into methane gas, which is used as fuel in kitchen stoves or electricity generators. In the case of a farm, for example, the gas generated by the faeces of the chickens is used to heat the eggs in the incubators. The solid residue left over in the biodigester can also be used as fertilizer.

“The organic material used must not contain toxic products, as they would kill the bacteria responsible for producing the gas”, says agronomist João Antônio Galbiatti, from the State University of São Paulo (Unesp). To manufacture the device, a hole is usually dug in the ground, sealing it with cement and bricks. A door must be left to place the residues inside the biodigester and be able to remove them later. The gas can be withdrawn through a pipeline.