Terra Preta Toilets
Dorothee Spuhler, seecon gmbh
Terra Preta Toilets
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will make the local water and sanitation system more sustainable. The main aim of the SSWM Toolbox is to be a reference tool to provide
ideas for improving the local water and sanitation situation in a sustainable manner. Results depend largely on the respective situation
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Terra Preta Toilets
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Contents
1. Concept
2. How it can optimise SSWM
3. Design Principals
4. Treatment Efficiency
5. Operation and Maintenance
6. Applicability
7. Pros’ and Cons’
8. References
Terra Preta Toilets
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1. Concept
What are Terra Preta Toilets?
Terra Preta Toilets are sustainable dry sanitation systems in four steps:
Collection - Lacto-fermentation – Vermicomposting – Terra Preta
Sources: GENSCH (2010 b); OTTERPOHL (n.y. b); GUENTHER (2007)
The main features are:
• Urine Diversion
• The addition of a special microbial mix to the separately collected urine
and faeces (conservation of nutrients via processes similar to lactofermetnation)
• The addition of charcoal to faeces
• Production of fertile black soil similar to Terra Preta by vermicomposting
Terra Preta Toilets
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1. Concept
What is Terra Preta?
Terra Preta is the name for the special human made black soil in South
America. It was generated by preColumbian native populations by
incorporation of charred residues
(charcoal) together with nutrient rich
material (kitchen waste, excreta,
bones, ash residues etc.) into the soil.
Charcoal is the black residue consisting
of impure carbon obtained by pyrolysis,
the heating biomass in the absence of
oxygen.
This black carbon is stable and remains
in the soil , further it acts like a sponge
for water and nutrients in the soil
making it extremely fertile.
Terra Preta Toilets
A typical arid soil from the Amazonian region
(Left). The fertile, carbon rich and fertile
Terra Preta soil (right). Source: GUENTHER (2007)
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1. Concept
How does it work?
Terra Preta Toilet collect urine and faeces separately.
To both, urine and faeces, a mix of anaerobic microorganisms is added.
Faeces are lacto-fermented (much like yogurt) by the microorganism in
anaerobic conditions transforming the organic matter and nutrients into earth
conserving carbon and nutrients.
The microbial mix in the urine prevents the bacterial urease process, that
transforms urea into ammonia (NH3) and carbon dioxide (CO2). (This is normally
happening when urine is conventionally stored leading to NH3 and CO2 loss to
the atmosphere). Urine is transformed in a nitrogen rich liquid fertiliser.
Faeces are further transformed into stable compost, similar to Terra Preta, by
worm enhanced composting (vermicomposting).
Kitchen wastes can be treated the same way as the faeces and any other
organic waste of the household can be added to the vermicompost.
The combined treatment results in no gas emissions and thus no odour and no
pollution of the atmosphere
Terra Preta Toilets
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2. How can it optimize SSWM?
Terra Preta Sanitation can be applied to any kind of urine diversion
dehydration or composting toilet. Thus it provides a safe on-site
waterless sanitation system. Solid organic wastes (from the kitchen or
garden) can be treated together with toilet products.
Waterless means, no water is required and no water is polluted and
needs to get cleaned/treated again.
The final product of these systems is a compost with similar properties
as the highly fertile Terra Preta. Terra Preta can be incorporated into
the soil, nutrients are recycled on a local level and food production
is increased.
In Terra Preta, no gases are produced, reducing thus emission of
greenhouse gases, caused by traditional sanitation. The carbon
remains in the soil in a stable form (black carbon) for centuries
contributing to the carbon sequestration (CO2) from the atmosphere.
Terra Preta Toilets
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3. Design Principals
Main elements of Terra Preta Toilets
Terra Preta toilets can be newly constructed or adapted from any other
existing toilet (e.g. UDDT, composting toilet). Mandatory design
elements are:
Microbial
mix
Airtight faeces
A toilet
collection
(including
chamber
superstruct
ure, seats
and slabs)
(Vermi)com
Airtight
urine
collection
vessel
Urine
diversion
-posting
site
Sources: GENSCH (2010 b); OTTERPOHL (n.y. b); GUENTHER (2007)
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3. Design Principals
Overview on the Terra Preta Sanitation process
Terra Preta Toilets
adopt the Terra
Preta Sanitation
(TPS) approach to
urine diverting
toilets.
TPS is:
(1) Collection
(2) Lacto-fermentation,
(3) Addition of charcoal
and vermicomposting,
(4) Incorporation of terra
preta compost into soils.
Sources: TILLEY et al. (2008); GENSCH (2010 b); GUENTHER (2007)
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3. Design Principals
Urine Collection
Urine can be collected in any airtight, sealable container. Most simple
urine collection containers are jerrycans
The microbial mix is introduced into the urine container before use.
• About 0.5 L for a 20 L jerrican of the microbial mix. (GENSCH 2010 b)
In normal conditions, urea contained in the urine is lost to the
atmosphere as ammonia (NH4) and carbon dioxide (CO2) via a process
called urease. With the microbial mix, urease is prevented:
◦ No gas emission
◦ No bad odour
◦ Conversion of NH4 and CO2 in the urine
◦ High fertilising value of urine
After 1 month to 6 month (OTERRPOHL n.y. a; FACTURA et al. 2010), the urine can be used as
liquid fertiliser or added to vermicompost to enrich it in nutrients.
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3. Design Principals
Faeces Collection
As for urine, any sealable bucket can be used as collection chamber.
The microbial mix is added after each use or after the bucket is full.
• The container is sealed after each use
• The container is sealed after it is full and left beside for lactofermentation
Lacto-fermented for at least 1 month (-6 month) (OTERRPOHL n.y. a; FACTURA et al. 2010).
• Carbon and nutrients are transformed to stable soil
• No gases, no odour
Addition of charcoal mix
• To add black carbon
• No humidity, no odour
In vermicomposting, the faeces with the added mix are transformed
into black earth and humus, similar to Terra Preta.
Terra Preta Toilets
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3. Design Principals
Lacto-fermentation and vermicomposting
Lacto-fermentation
• A microbial process used for
sterilisation in food industry
(e.g. yogurt, Sauerkraut, etc.)
• Pathogens are killed (due to
acidity)
• No gases, thus no volatilisation
of organic matter or nutrients
Source: OTTERPOHL (n.y. b)
Terra Preta Toilets
Vermicomposting
• Earth worms break down
organic matter together with
nutrient rich matter
• Their cast forms complex
humus molecules
• Organic matter and nutrients
are conserved in the soil
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3. Design Principals
Added material
Charcoal mix:
Charcoal
Stone dust
Finely cut wood
Some limestone or volcanic
soil
Wood can be replaced with any
other bulking agent to raise
C/N necessary for
vermicomposting.
The mix can be prepared in
advance and stored close to
the toilet (keep it dry!).
•
•
•
•
Microbial mix:
Similar to commercial available
effective microorganisms (EM) mix,
but specifically designed to prepare
for vermicompost and for free!
• Bacillus subtilis, Bacillus mesentericus,
Geobacillus stearothermophilus, Azotobacter
croococcum and Lactobacillus
• Available at the Technical University HamburgHarburg (TUHH, Institute of Wastewater
Management and Protection, aww, Germany) or
from the Xavier University Sustainable
Sanitation Center (Philippines)
To prepare a lacto-fermentation
microbial mix, on can also take an
Inoculum from Sauerkraut liquor.
Picture sources: OTTERPOHL (n.y. b); GENSCH (2010 a)
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4. Treatment Efficiency
Health aspects
Lacto-fermentation is an established process for food sterilisation in
the food industry.
Vermicomposting is an established process for the treatment of organic
waste and has also been applied to faeces and faecal sludge. (BUZIE and
OTTERPOHL n.y.; OTTERPOHL n.y. b)
• A recent publication indicates a 99 % inactivation of indicator
bacteria. (FACTURA et al. 2010)
• But the process is still new and the effect on other organism (more
persistant pathogenes) requires further investigations!
Source: FACTURA et al. (2010)
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4. Operation and Maintenance (O&M)
Operation and maintenance for Terra Preta Toilets are relatively low, but crucial
for a good sanitation!
• Main tasks
◦ Add microbial mix and charcoal mix
- Urine tank: before use
- Faeces chamber: either after each use or before lacto-fermentation
◦ Control airthightness of faeces and urine tank
◦ Clean urine pipes from deposits
◦ Change the urine and faeces tank when necessary
• Vermicomposting: check moisture and temperature
• Preparation and maintenance of the stock microbial mix (GENSCH 2010 b)
◦ Feed the the microorganism once a week with some water and sugar
source (blended bananas, sugar cane juice etc.) which as been cooked
and cooled down previously (for sterilisation)
◦ Sugar content of the solution 3 to 5 %
◦ Label the bottles containing the microbial mix and keep them away from
children
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5. Applicability
Terra Preta Sanitation can be applied to every toilet in any climate
(even though high temperatures enhance the process) at household,
institutional of community level.
• Compulsory criteria are
◦ A separate collection and storage facility for urine and faeces
◦ Space for vermicomposting
◦ Need for liquid fertiliser (urine) and Terra Preta
◦ Availability of charcoal and microbial mix
• They are particularly adapted to
◦ Urban or indoor toilets as no gas and no odour is produced
◦ Where soil degradation is an issue
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6. Pros’ and Cons’
Advantages:
Disadvantages:
• No odour and no need for ventilation
• Relatively new technology
or dehydration system
(requires further research)
• Urine, faeces as well as organic
wastes can be treated together
• Operation and maintenance is
low, but crucial for correct
• Requires little space
functioning (e.g. growth of
• Production of liquid fertiliser and
microbial mix)
highly fertile, long lasting soil (Terra
Preta)
• Need for Terra Preta compost
and urine fertiliser required
• Contributes to reducing green house
gas emission
• Potential for carbon sequestration
• High pathogen reduction
Terra Preta Toilets
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7. References
FACTURA, H., BETTENDORF, T., BUZIE C., PIEPLOW H., RECKIN J., OTTERPOHL R. (2010): Terra Preta Sanitation: rediscovered from an ancient Amazonian civilisation - integrating sanitation, bio-waste management and agriculture. In:
Water Science and Technology, accepted for publication
GENSCH, R. (2010) a: Terra Preta Sanitation (TPS) Workshop, April 5-8, 2010. Cagayan de Oro City: Sustainable
Sanitation Center, Xavier University
GENSCH, R. (2010) b: Terra Preta Sanitation. Overview. Cagayan de Oro: Xavier University, Sustainable Sanitation
Center
GUENTHER, F. (2007): Carbon sequestration for everybody: decrease atmospheric carbon dioxide, earn money and
improve the soil. In: Energy and Environment submitted (27.03.2007).
Available at: http://www.holon.se/folke/carbon/Terra%20pretav1_0.pdf [Accessed: 10.05.2010]
OTHERPOHL, R. (n.y.) a: Terra Preta Sanitation- full reuse in sanitation and bio-waste-management. Hamburg: Institute
of Wastewater Management and Protection (aww), Technical University Hamburg-Harburg (TUHH).
Available at:
http://www.tu-harburg.de/susan/downloads/index.html [Accessed: 11.05.2010]
OTTERPOHL, R. (n.y) b: Waste Water Reuse in Buildings. Hamburg: Institute of Wastewater Managemetn and Protection
(aww), Technical University Hamburg-Harburg (TUHH).
TILLEY, E., LUETHI, C., MOREL, A., ZURBRUEGG, C., SCHERTENLEIB, R. (2008): Compendium of Sanitation Systems and
Technologies. Duebendorf and Geneva: Swiss Federal Institute of Aquatic Science (EAWAG) & Water Supply and
Sanitation Collaborative Council (WSSCC) Available at:
http://www.eawag.ch/organisation/abteilungen/sandec/publikationen/compendium_e/index_EN Accessed:
09.04.2010]
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