Rainy day in Gorak Shep
Water in sufficient quantity must be collected, transported and stored until needed for input into the reactor. It will be heated immediately before mixing it with human waste so that the daily slurry feed does not reduce the temperature inside the reactor.
Possible sources of water include:
- Harvested rainwater from rooftop runoff in the monsoon season
- Water collected/transported from nearby sources
- Melted snow/ice
- Kitchen waste
- Effluent from digester
A combination of rainwater harvesting and effluent recycle is the best solution, for the following reasons:
Based on six years of local weather data and our own calculations, a water-collection system, which is a gutter that drains into a barrel, on the roof of the greenhouse would collect enough rain during the monsoon season to run the reactor. The water needs to be stored near the biogas reactor and kept above freezing. The container will be a series of large plastic barrels like those that are currently being used to transport the human waste from the base camps. Storing them inside the greenhouse would keep them from freezing, but the total volume that needs to be stored is still an issue.
Another source of water would be to recycle water from the effluent, as it is still mostly water as it comes out. This would lower the amount that needs to be stored. A settling tank at the end of the reactor could be used to help separate the water from the waste. A secondary benefit is that recycling the effluent back into the reactor can increase the gas output.