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Composting human waste from waterless toilets
J. F. Hanssen*, A. Paruch**, P. D. Jenssen**
* Department of Biotechnology and Chemistry
** Department of Mathematical Sciences and Technology
The Norwegian University of Life Sciences
3rd. International Conference on Ecological Sanitation, Durban May 24. 2005
Composting toilet
Collection/composting compartment
Liquid overflow collection
Vent pipe
Composting toilet
• Major toilet type in Norwegian cottages (500 000 cottages)• Commonly used in rural homes in Norway • Used in many other settings world wide
Composting toilet at roadside facility - Sweden
Elected the best roadside facilityIn Sweden 2002
Composting toilet at roadside facility - Sweden
Clean odourlesstoilets
Antartica 2001The compost reactor presented herein was tested when Erik Sønneland (picture) and Rolf Bae spent almost one year on the south pole preparing for crossing the whole Antartica. See also:http://www.polarhistorie.no/hendelser/1209014134.59/tidslinjehendelse_view?geografi=&hovedemne=&underemne=&hovedepoke=&underepoke=&
and
http://www.adlibris.com/no/product.aspx?isbn=8292309020
Secondary composting
Volume reduction:• 70 - 90%• 550 down to 55 liters
(Del Porto and Steinfeld 2000)
Composting toilet
Composting toilet
• Nitrogen loss• To wet/dry• Hygiene
NH3
Composting toilet
• Nitrogen loss• To wet/dry• Hygiene
To much liquid
Composting toilet
• Nitrogen loss• To wet/dry• Hygiene
Composting toilet
• Nitrogen loss• To wet/dry• Hygiene - no system above 43oC* - risk of handling
(* Engen 1991)
Composting toilets - some challenges
• Minimize risk when handling/emptying• Ensure a hygienized compost• Minimizing the nitrogen loss during composting
of nitrogen-rich waste• Minimizing the odour emission during
composting
Secondary composting
Composting bioreactor Final hygienized
product
Secondary composting
Compost laboratory
The compost bioreactor
x
Compost
Screen
Vacuum pump
Liquid container
Total volume 750 liter
Return of process water - rich in NH4+
Input to the composting bioreactor
Influence of time and temperature on destroying pathogens in excreta
(Feachem et al. 1983)
Temperature in compost vs. time
Temp oC
Days
Results
Temp vs.time Run no.1 Temp vs.time Run no.2
Temperature vs. time
The compost bioreactor - process control
x
Compost
Screen
Vacuum pump
Liquid container
Return of process water amount and frequency
The compost bioreactor - process control
x
Compost
Screen
Vacuum pump
Liquid container
Return of process water amount and frequency
Temperature vs.time and addition of process water
The compost bioreactor - process control
x
Compost
Screen
Vacuum pump
Liquid container
Pumpingfrequency
Ammonia volatilization
NH3 NH4 +
• Recycling of process water
• Controlling air flow• Addition of bulking
material
The compost bioreactor - process control
• Recycling of process water
• Controlling air flow• Addition of bulking
material• Manual mixing
The compost bioreactor - process control
Conclusions
• A composting bioreactor for processing of human excreta with other biodegradable organic waste is developed
x
Compost
Conclusions
• The composting bioreactor reduce the nitrogen loss compared to windrow composting, thus producing a more valuable compost
x
Compost
Conclusions
• Secondary composting can produce a safe soil amendment in about two months – in contrast to the generally recommended six months
Recommendations
•At least 15 cm of bark should be placed above the filtration screen to enhance leachate drainage.
•Food waste should be chopped to at least 5 cm dimensions.
•Although meat and fish products can be added, large bones should be removed.
•Food waste and excreta should be mixed, not layered.
The leachate evacuation hose should be insulated if exposed to cold temperatures.
The reactor needs weekly maintenance
• Different concentrations of leachate recycled at different times
• Different volumes of different bulking agents
• Different mixing schedules
• Investigate dieoff of other organisms than coliforms
Further investigations
Conclusions
• Secondary composting opens for professional collection and treatment of material from composting toilets- thus reducing risk
References:
Engen, Ø. 1991. Hytteklosetter-Alternative avløpsløsninger for hytter og spredt bebyggelse, med hovedvekt på miljøkonsekvenser. SFT/JORDFORSK report no. 1207, Centre for Soil and Environmental Research, Ås, Norway, 68p.
Del Porto, D. and Steinfeld, C. (2000). “The Composting Toilet System Book”. Ecowaters Books, Concord, Massachusetts.