How do I generate electricity from feces?

Answer

Hi Eddie,

Collecting animal excrement, for example on large farms, to subsequently generate energy, is indeed a technology that is becoming more and more accepted, and not just because it generates energy in an ecological way. It also has the advantage of reducing the amount of manure, and it is a way of supplying energy to places where the electricity grid is not reliable or available. For example, read “West African families cook on cow dung” from De Morgen of 20/09/2011.

Now, how does the process work? In fact, it comes down to collecting biogas. This is a gas mixture that is produced when organic material (such as animal excrement, kitchen waste, pruning waste…)
in the absence of oxygen is broken down: we call it “anaerobic fermentation”. This process is carried out by micro-organisms present in the organic material and requires a temperature of preferably more than 30°C. For example, it will be less interesting to produce biogas in Northern Canada than in say Central Africa. Under these conditions, the micro-organisms convert the organic compounds in a complex series of chemical reactions into, among other things, methane, CO₂heat and also, for example, sulfur compounds.

These gases, which as you can see are mainly greenhouse gases, are captured. Particularly interesting is the presence of methane. This gas can be burned under oxygen-rich conditions to provide heat, for example in developing countries where the biogas is often used for cooking. Another option is to use the biogas to power a generator, which then supplies electricity. The gas can also be purified (for example to remove the sulfur compounds) and then you can use it to power engines, for example.

Conclusion:
Organic waste –> anaerobic digestion –> biogas –> energy –> electricity.

Regards,
Benjamin