Before I entered the field of cleantech, I rarely thought of human waste. Like most civilized folks, I just avoided thinking about it!
But in the past few years, I have seen how human waste management is a critical challenge for most countries, and more so for developing and under-developed nations.
While most people consider managing and treating human waste as a cost center, it really need not be, because human waste can be converted to energy.
Many folks are surprised when they hear that human waste (and animal waste) can be used to generate electricity.
How is this done?
You see, human waste comprises mainly two components – water and organic materials – apart from some amount of inorganic materials, micro-organisms (mainly bacteria).
At sewage treatment plants, the organic waste is separated from water such that it results in a semi solid sludge.
This wet sludge (mostly organic) can be fed to biodigesters, equipments in which there is an anaerobic environment (essentially, no oxygen present). In such an anaerobic environment, certain types of bacteria feed on the organic material and release biogas.
Now, biogas contains about 50% methane., and methane is a gas with high energy content – the natural gas we are familiar with is just methane!
So! We get biogas from the digesters, thanks to the friendly bacteria.
To generate power, biogas is typically used in gas engines, equipment not very different from our back-up diesel generators. Only, in this case, the fuel is not diesel but is biogas.
That. Is. It.
A few years back, I recall visiting a sewage treatment plant (STP) not far from my house. The whole operation of sewage waste to power is a fairly neat and simple process. The power generated from sewage waste was enough to run all the operations for the STP, so it was actually self-sufficient in power generation. In fact, they were exploring avenues to export to the grid some surplus power they were generating!