According to professor Nomad of the Netherlands, never
There, the waste material is brought to normal air pressures and a yeasting reaction starts - producing methane and CO2 which can be used to produce electricity. The first estimates predict that about 10 percent of the houses (so 3 out of a total of 32) can be sufficiently powered this way.
Or are you wondering how large a community has to be before it can build the infrastructure necessary for 10% of its energy to come from poop? Those whom the Gods wish to destroy They first make mad. -- Euripides
But also: Is there a point (scale) that the return gets larger than 10 percent? If we have 500 people, do we get a larger return, say 15%, or will it always be 10%? I've learned in Sweden that a follow-up for some 500 houses in Sneek with the same sewage system is practically go, so we might actually get an answer on that question - in a few years.
