So we’ve been doing some investigation into installing biogas into schools which are using huge amounts of firewood for their cooking needs. These are BIG institutions! We’re talking upwards of 1500 boarding students!
There are a lot of challenges with biogas even at a small scale. Most notably for me the pure amount of unsavoury work it takes to feed the beast! The calculations say that about 60% of fuel needs can be met by Biogas…best case.
These schools happen to have a huge problem with sanitation as well. With no water borne sewage they rely on pit latrines. The maintenance of these systems (either digging new ones, or emptying them) imparts another financial cost of the schools. Not to mention the possible damage to the ground water system! In the area we are working there is no ‘honey sucker’ truck to dispose of human waste…it’s dumped on site, in pits on the school grounds!
So is it possible to feed a biogas digester with human waste? Yes it is. The problem however is getting enough of it into the digester. The traditional answer to this has been to build latrine stances which feed, by gravity, directly into the digester…cost cost cost.
The idea now is to retro fit digesters to existing latrines so as to cut the cost of construction, give a relatively easily sustained supply of biogas, to reduce expenditure of firewood and latrine maintenance, and to partially treat the human waste.
- Sintex’s biogas digester ingests shit, emits energy (croeso.typepad.com)
- Non-profit to turn Toronto Zoo waste into Green Energy (thegreenenergyblog.com)