Pee and Poo
http://www.buzzfeed.com/andrewgauthier/the-crazy-amount-of-stuff-your-body-makes-in-a-year
130 gallons and 360 lb.
Energetics of Incineration
8.33 lb in 1 gallon
1 BTU = 1 lb water raised 1 F
160F raise to boil from 60.
1300 BTU till boiling.
3400 BTU per kWh
[1] - 2300 kJ to vaporize one kg
~10MJ for one gallon.
1/3 kWh for one gallon to get it to temperature, then about 3 kW hr per gallon to vaporize.
If have 500W of panels, that could do one person if you have 6 hours of sunlight per day.
Moisture of Poo is 75% - [2]
Thus, Poo itself would require 50W of solar panels to incinerate if liquids are separated.
30MJ - charcoal enervy per kg. 1/3 kg charcoal per day to do the job.
Proposed Solution
Advanced biofilter is required. If separate urine, handling liquid is not much more effort.
Heavy waste loading means that the energy content must be extracted in some form. The question is what form. Options:
- Safe powder from shit fryer.
- Liquids are used to grow algae.
- Aerobic biofilter processes all waste, generates worms. Requires high inputs of carbon.
- Biogas digester - anaerobic, and final product is fertilizer + cooking gas. This gets into volumes required. Tank under toilet is a good idea. Top oil film for smells is a good idea. Allows flushing capacity.
- Baseline is 1 cubic meter per person to handle waste, and fertilizer comes out the other side.
Conclusions
There is no better alternative for waste processing than biogas digesters - on grounds of net positive energy output as well as fertilizer production.
One issue is materials handling - so the optimal system would have to have a garden attached to use the fertilizer, or be part of a composting operation where a lot of carbon is applied.
Principles to apply:
- Must be part of an integrated system with Aquaponics and garden.
- Must integrate with cooking gas infrastructure - an extra bonus.
- To be acceptable publicly, must use existing interfaces (such as toilet and septic tank concept). Can meet reticulation as septic tank plus flush toilet.
- Water purification is the most advanced aspect of this. This would require redworm towers plus algae bioreactor plus Aquaponics to strip nutrients, carbon filter for final purification step.