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Introduction to composting Course 2 Unit 6 Part c and d Teacher: Mariska Ronteltap

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1 Introduction to composting Course 2 Unit 6 Part c and d Teacher: Mariska Ronteltap

2 * Engineered = manufactured with a composting chamber – unlike the Arborloo (see Course 1 Unit 3), which works like a very basic soil composting toilet (good for rural areas) The term “dry toilet” is often used for composting toilets, but once again, this can be misleading. Example: Dry Toilet Club of Finland Part C – Engineered composting toilets Part D – Examples and case studies

3 Engineered composting toilets – overview Composting toilets are more difficult to operate than dehydrating toilets, e.g. they need optimal moisture content for the biological process of composting  therefore, composting toilets are less applicable for most sanitation projects in low-income countries (compared to UDD toilets) Proposed optimal conditions for micro-organisms responsible for composting:  Moisture content range from 50-60%, <70%  Temperature below 70°C, optimum between 35°C –55°C  C/N ratio approximately 30:1  pH value 5.5 – 8.5  Oxygen concentration >10% Composting toilets can also treat household organic waste (this increases the C/N ratio) It is useful to know what the composting toilet market looks like in Europe (to prove that toilets without water are not just for poor people in developing countries!) Course 2 Unit 6

4 Composting toilets, example Berger Biotechnik The following 5 slides were provided by Wolfgang Berger, whose company (Berger Biotechnik GmbH) is the market leader for composting toilets in Germany  “Since 1985 we have sold about 450 TerraNova-Composting toilet systems and about 15,000 biological dry toilets (SAWI, TOA, Separett u.a.). TerraNova, SAWI and TOA are our own products. In the last 5 years, there were about 25 larger projects (number reducing) and about 3000 small systems (stable figures).  The main market for our big projects (TerraNova) is Germany, Austria, Switzerland, but also several islands in the Mediterranean or Atlanic.” BERGER BIOTECHNIK GmbH eMail: Internet: A publication by Wolfgang Berger on this topic is available under Extra Materials

5 Composting system for toilet and kitchen waste (indoors) Schematic of air ventilation Opening for emptying Composting container

6 Toilet pedestal with seal in lid Removable insert for easier cleaning Drop pipe from higher floors (straight fall for faeces) Toilet pedestals and drop pipes for faeces (can be with or without urine diversion)

7 10 m drop pipe for faeces with 0.3 m diameter; 14 m ventilation pipe with 0.15 m diameter 4-storey building with public Kindergarten (in Germany) Course 2 Unit 6

8 Use the natural slope to position the composting vessel below the toilet Public composting toilets in the Alps and national parks

9 After 2 years of composting, the compost can be applied as soil conditioner for flower beds, about 2 L per m² and year Final product – the loop is closed

10 Other examples of composting toilets (there are many suppliers on the market) BioLet Company: Nature Loo Company: Sun-Mar Company:

11 Costs of composting toilets They can be quite expensive technology-review-composting-toilets.pdf and 030-automated-compost-toilet-asahiyama-zoo- 2006.pdf technology-review-composting-toilets.pdf 030-automated-compost-toilet-asahiyama-zoo- 2006.pdf  Costs can be high due to proprietary designs  Often marketed at the high end market – e.g. for wealthy, eco-minded people in Germany They should not require a secondary treatment step for faeces anymore (this is integrated into the toilet) Course 2 Unit 6

12 Video clips on composting toilets There are many video clips on YouTube on this topic (mostly composting toilets without urine diversion), e.g.  (short documentary of National Geographic) Urine-diversion composting toilet at a Germany adventure playground: 

13 Course 2 Unit 6 Part D: Examples and case studies Course 2 Unit 6

14 Example 1: Home composting of dried faeces and kitchen waste (garden of Richard Holden, Johannesburg, South Africa)

15 Back to Richard Holden’s house in Johannesburg, South Africa: Richard adds the faeces bucket of his UDD toilet to his composting heap (a handfull of compost is added to the bin after each defecation event, as well as toilet paper) (remember: this system was mentioned already in Course 1 Unit 3 Part E) this is not Richard Holden, but my husband Steve, demonstrating how it is done

16 Composting unit at front of house (note gaps in bricks for ventilation)

17 The compost is removed from the bottom of the heap with a spade (and the compost is then taken to a second composting heap in the back garden (see next slide)) Course 2 Unit 6

18 Final compost product; also used to line faeces bin and as additive to faeces bin after defecation Second compost heap in the garden, on which urine is applied (urine jerry can is emptied manually onto that compost heap twice per week). The photo shows Elisabeth doing this activity (actually quite difficult to do this! - heavy)

19 More practical details on Richard’s home composting system Internal dimensions: 600 x 700 mm (900 mm above ground and 400 mm below ground) One lintel* across the body of the composter above the lower opening to hold the compost up. The composter can be made from anything, mud block wood etc. The secret is to keep moist, aerobic and turn. Also the composter has kitchen waste in it (far more in volume terms than the excreta), toilet paper and the dry soil that is used for odour control. As for pathogen destruction Chris Buckley in KZN was testing a sample, Aussie Austin at CSIR has already. The problem is that the family doesn't have worms so cannot test for them. Temperature, time and biological activity all contribute to making the contents safe. Recently in my garden compost I threw a dead rat. In less than one month all trace of the rat had disappeared. Lately I have been adding a comfrey** soaked in water over 10 days. It smells like raw sewage but seemd to turbocharge the composting process. *Lintel: a beam across something ** Comfrey is some herb Source: E-mail from Richard Holden, May 2007

20 Example 2: Co-composting of faecal sludge with organic solid waste The following five slides were provided by Doulaye Koné, SANDEC/Eawag, Switzerland ( - this technology will also be mentioned again in Course 2 Unit 7 (faecal sludge management) “Co-composting” means: having two (or more) different input materials Course 2 Unit 6

21 Case study: Co-composting of faecal sludge with organic solid waste in Kumasi, Ghana (1/5)  Faecal sludge is high in N; organic solid waste is high in C; together they give a suitable C:N ratio for composting  Investigated impact of turning compost heap at pilot scale  Operated one month at high temperature and 3 months in total  Measured indicator is helminth eggs Reminder: Faecal sludge = urine, faeces and some water Mature compost during curing phase

22 22 Discharge of faecal sludge Sludge drying beds Organic solid wasteCompost maturation Co-composting process (2/5) Dewatered faecal sludge (solids) Liquid (drainage) to other treatment

23  Temperature was higher than 45°C for 4-6 weeks (this results in pathogen kill) Heap 1, turned when temp > 60 Heap 2 turned each 10 days 30 45 60 75 010203040506070 Days Temperature (C) Heap11Heap12 Heap21Heap22 Temperature development during co-composting of dewatered FS and organic solid waste (3/5)

24  Number of helminth eggs (HE) in final product: < 10 / g d.s.  Viability of helminth eggs in final product: < 10 %  Co-composting ensures hygienisation  Recommendation for use of biosolids in agriculture: 3-8 HE / g d.s. (based on WHO ww reuse guidelines; Xanthoulis + Strauss, 1991)a Ascaris egg inactivation, results from pilot-scale co-composting (4/5) Course 2 Unit 6 Days of composting Total number of eggs per g d.s. Viable number of eggs per g d.s. Number of eggs per g d.s. Final product

25 25 Optimum mixing ratio (regarding porosity, humidity, C/N): FS* : other compostable materials = 1: 3-10 *75-96% water content Co-composting design criteria (5/5) Design criteria: -C/N ~ 25-30 -Humidity ~ 50-60% -pH ~ 6-8 -Windrow size  1 m 3 -Aeration (forced or natural) Process measurements: -Temperature measurement (expect T=55-65°C during thermophilic phase) Approximate C/N ratio for some compostable materials 1 : -Nightsoil ~ 6-10 -Weeds ~ 19 -Farmyard manure ~ 14 -Wheat straw ~ 128 -Fresh sawdust ~ 511 -Fruit wastes ~ 35 -Refuse ~ 30-80 1 Obeng and Wright (1987) The Co- composting of Domestic Solid and Human Wastes UNDP/World Bank

26 Relevant websites Composting in general:  (organisation in Germany which issues the quality assurance certificates for compost; site contains only little information in English  (The Network is a collaboration of partners, promoting sustainable practices in composting, anaerobic digestion and other treatment procedures for organic residues across Europe. It aims to address the needs of both practical operators and decision makers.) Composting toilets   (Dry Toilet Club in Finland)

27 References Tchobanoglous, G., Burton, F.L., Stensel, H.D. (2003) Wastewater Engineering, Treatment and Reuse, Metcalf & Eddy, Inc., McGraw-Hill, 4th edition. This is a good general conventional wastewater treatment book Rothenberger, S., Zurbrügg, C., Enayetullah, I., and Maqsood Sinha, A. H. M. (2006) Decentralised composting for cities of low- and middle-income countries - A users' manual, Eawag/Sandec (Switzerland) and Waste Concern (Bangladesh), Dübendorf, Switzerland. Available: * Vodounhessi, A., and von Münch, E. (2006) Financial and institutional challenges to make faecal sludge management integrated part of ecosan approach: Case study of Kumasi, Ghana. Water Practice and Technology (selected proceedings of the Beijing Biennial IWA Congress), 1 (2) Available:

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