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.