Transcript Document

Course 2 Unit 6
Part c and d
Introduction to composting
Teacher: Mariska Ronteltap
[email protected]
Part C – Engineered composting toilets
Part D – Examples and case studies
* 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
Course 2 Unit 6
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!)
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.”
A publication by Wolfgang
BERGER BIOTECHNIK GmbH
eMail: [email protected]
Internet: www.berger-biotechnik.de
Berger on this topic is
available under Extra
Materials
Composting system for toilet and kitchen waste (indoors)
Schematic of air
ventilation
Composting container
Opening for emptying
Toilet pedestals and drop pipes for faeces
(can be with or without urine diversion)
Toilet pedestal with
seal in lid
Drop pipe from higher floors
(straight fall for faeces)
Removable insert for
easier cleaning
Course 2 Unit 6
4-storey building with public Kindergarten (in Germany)
10 m drop pipe for faeces with 0.3 m diameter; 14 m ventilation pipe with 0.15 m diameter
Public composting toilets in the Alps and national parks
Use the natural slope to position the composting vessel below the toilet
Final product – the loop is closed
After 2 years of composting, the compost can be applied as soil conditioner
for flower beds, about 2 L per m² and year
Other examples of composting toilets (there are
many suppliers on the market)
BioLet Company:
http://biolet.com/products/ne.htm
Nature Loo Company:
http://www.nature-loo.com.au/toilets/systems/ensuite.html
Sun-Mar Company:
http://www.sun-mar.com/products/excelne.php
Course 2 Unit 6
Costs of composting toilets
They can be quite expensive
http://www.gtz.de/en/dokumente/gtz2009-entechnology-review-composting-toilets.pdf and
http://www.gtz.de/en/dokumente/en-ecosan-pds030-automated-compost-toilet-asahiyama-zoo2006.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)
Video clips on composting toilets
There are many video clips on YouTube on this topic
(mostly composting toilets without urine diversion),
e.g.
 http://youtube.com/watch?v=wNMs9oiPuvo (short
documentary of National Geographic)
Urine-diversion composting toilet at a Germany
adventure playground:
 http://www.c-studios.net/ecosan/
Course 2 Unit 6
Course 2 Unit 6
Part D: Examples and case studies
Example 1: Home composting of dried faeces
and kitchen waste (garden of Richard Holden,
Johannesburg, South Africa)
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
Composting unit at front of house
(note gaps in bricks for ventilation)
Course 2 Unit 6
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))
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)
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
Course 2 Unit 6
Example 2: Co-composting of faecal sludge
with organic solid waste
The following five slides were provided by Doulaye Koné, SANDEC/Eawag,
Switzerland (www.sandec.ch) - 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
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
Mature compost during curing phase
Reminder: Faecal sludge = urine, faeces and some water
Co-composting process (2/5)
Sludge drying beds
Discharge of faecal sludge
Liquid
(drainage)
to other
treatment
Dewatered
faecal sludge
(solids)
Organic solid waste
Compost maturation
22
Temperature development during co-composting of
dewatered FS and organic solid waste (3/5)
Heap 1, turned when temp > 60
Heap 2 turned each 10 days
Temperature (C)
75
Heap11
Heap12
Heap21
Heap22
60
45
30
0
10
20
30
40
50
60
70
Days
 Temperature was higher than 45°C for 4-6 weeks (this results
in pathogen kill)
Course 2 Unit 6
Ascaris egg inactivation, results from pilot-scale
co-composting (4/5)
Elimintion des Oeufs d'Ascaris par co-compostage avec déchets organique
ménagers: Résultats d'expérimentation à Kumasi/Ghana
Nbr. Oeufs
d'Ascaris
/gg
MSd.s.
per
of eggs
Number
40
Total number of eggs per g d.s.
Nbr. Total oeufs d'ascaris g / MS
Nbr.
oeufs
d'ascaris of
viables
g / per
MS
Viable
number
eggs
30
20
g d.s.
Final product
10
0
0
30
60
90
Temps
(jours)
Daysde
ofcompostage
composting
 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
Co-composting design criteria (5/5)
Design criteria:
Approximate C/N ratio for some
compostable materials1:
C/N
~ 25-30
Humidity ~ 50-60%
pH ~ 6-8
-Windrow size  1 m3
-Aeration (forced or natural)
-
Process measurements:
Temperature measurement
(expect T=55-65°C during
thermophilic phase)
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 Cocomposting of Domestic Solid and
Human Wastes UNDP/World Bank
Optimum mixing ratio
(regarding porosity, humidity, C/N):
FS* : other compostable materials = 1: 3-10
*75-96% water content
25
Relevant websites
Composting in general:
 www.kompost.de (organisation in Germany which issues
the quality assurance certificates for compost; site
contains only little information in English
 www.compostnetwork.info (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
 www.berger-biotechnik.de
 www.drytoilet.org/index.html (Dry Toilet Club in Finland)
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:
www.sandec.ch. *
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: http://62.189.20.32/wpt/001/wpt0010045.htm