Agricultural Aspects of Sustainable
Sanitation & Water Management
Robert Gensch, Xavier University
Agricultural Aspects of Sustainable Sanitation & Water Management
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Agricultural Aspects of Sustainable Sanitation & Water Management
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Contents
1. Background
2. Global/Local Resource Limitations
3. Reuse and Safe Discharge Options
4. Health Considerations
5. Benefits
6. References
Agricultural Aspects of Sustainable Sanitation & Water Management
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1. Background
Plant requirements
Light
Nutrients
Macronutrients
Carbon
Dioxide
Water
Soil
Structure
Nitrogen (N)
Phosphorus (P)
Potassium (K)
Sulphur (S)
Magnesium (Mg)
Calcium (Ca)
Micronutrients
Boron (Bo)
Copper (Cu)
Iron (Fe)
Chloride (Cl)
Manganese (Mn)
Molybdenum (Mo)
Zinc (Zn)
Plant requirements Source: R. Gensch
Agricultural Aspects of Sustainable Sanitation & Water Management
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1. Background
Flow of Nutrients
Harvest
(incl. nutrients & organic matter)
Animal manure
Compost
Human excreta
Fallow periods
Nutrient Flow Source: R. Gensch
Agricultural Aspects of Sustainable Sanitation & Water Management
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1. Background
Agricultural Production in Former Times
• Loss of soil fertility inherent to all
agricultural systems
• Nutrients are taken up from the soil
through the harvest, transported, eaten
and excreted
• In former centuries common practise to
compensate nutrient loss through
application of animal manure, human
excreta, compost or long fallow periods
• Human excreta contains all important
nutrients and organic matter necessary
for crop production
Source: rite.blogspot.com
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1. Background
Nutrient Consumption and Excretion
• Correlation between consumed nutrients and excreted nutrients
• About 99-100% of all consumed nutrients are excreted
2.7 kg/a Nitrogen
2.7 kg/a Nitrogen
0.4 kg/a Phosphorus
0.4 kg/a Phosphorus
1.5 kg/a Potassium
1.5 kg/a Potassium
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1. Background
Closing the Loop
FOOD
NUTRIENTS
FOOD
NUTRIENTS
Source: GTT, Photos: R. Gensch
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1. Background
Modern agricultural practises
• Flow of plant nutrients most often linear
• Nutrients are taken up from the soil, eaten,
excreted and discharged
• With production of synthetic fertilisers in the 19th
century it seemed feasible to uncouple from
ecological requirements
• The loss of most important macronutrients (N,P,K)
partly compensated through application of
synthetic fertilisers
• Despite of fertiliser use a negative nutrient balance
in most soils is observed
Source: rite.blogspot.com
Agricultural Aspects of Sustainable Sanitation & Water Management
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1. Background
Flow of Plant Nutrients
Harvest
(incl. nutrients & organic matter)
Polution
Health Risks
Animal manure
Compost
Human excreta
Fallow periods
Synthetic fertiliser
Agricultural Aspects of Sustainable Sanitation & Water Management
Availability
Affordability
Source: R. Gensch
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1. Background
Urbanisation
• Problems: water scarcity, food insecurity and
pollution based on the assumption that:
• There are no limits to resources such as water
and land
• The environment can assimilate the wastes
that we produce from using these resources
• Linear flows of resources and wastes that are
not reconnected
• 75% of natural resources harvested and mined
from the Earth were brought to 2.5 percent of
the earth's surface, metropolitan areas.
• 80% of the natural resources are converted into
waste, which are disposed of (Smit 2002)
Metro Manila Source: R. Gensch
Agricultural Aspects of Sustainable Sanitation & Water Management
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1. Background
Urbanisation
•
Massive flow of nutrients
o Food from rural areas to cities
o Nutrients (excreta): pits, lakes, waterbodies…
•
But:
o Nutrients and organic matter in excreta are
toxic to different life forms living in water
(sewage pollution)
o Biodiversity is threatened (Eutrophication)
o Soil fertility declines
Metro Manila Source: R. Gensch
Agricultural Aspects of Sustainable Sanitation & Water Management
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2. Global/Local Resource Limitations
Soil Degradation
Very high severity
High severity
Moderate severity
Low severity
Stable Land, Ice Caps or
non-used wasteland
Map of Global Soil Degradation Source: FAO
• The earth is losing 25 billion t/a of nutrient rich topsoil
• 2 billion ha of vegetated land degraded since 1945
Agricultural Aspects of Sustainable Sanitation & Water Management
(WWI 2005)
(UNEP)
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2. Global/Local Resource Limitations
Water Scarcity
• Within next 50 years more than 50 %
of world population will live in
countries with water stress or
scarcity (WHO 2006)
• Food production highly water
demanding process with around 70%
of all used water for agricultural
irrigation (Brown 2006)
• Alarming exploitation of ground- and
surface water resources
Potable water being piped to a rice field, USA source: McCabe
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2. Global/Local Resource Limitations
Limited Minable Fertilizer Resources
• Farmers worldwide require 150
million tons of synthetically
produced nutrients (IFA 2004)
• At the same time conventional
sanitation systems dump around 50
million tons of fertiliser equivalents
into water bodies
• Production of most common
synthetic fertilizer ingredients (N, P,
K) relies on non-renewable
resources
Source: Dagerskog, 2009
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2. Global/Local Resource Limitations
Limited Minable Fertilizer Resources
•
Global Phosphorus reserves almost
entirely from geological deposits and
expected to last for around 50-100 years
•
Potassium reserves expected to last for
about 300 years
•
Nitrogen can be extracted from the
surrounding air, but very energy-intensive
process
Source: J. Christiansen
Agricultural Aspects of Sustainable Sanitation & Water Management
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2. Global/Local Resource Limitations
Phosphorus Peak
Peak phosphorus ‘Hubbert’ curve
Agricultural Aspects of Sustainable Sanitation & Water Management
Source: Cordell, Drangert & WHite
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2. Global/Local Resource Limitations
Phosphorus Peak
Phosphorus resources worldwide Source: A. Rosemarin et al
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2. Global/Local Resource Limitations
Phosphorus Peak
9.1 billion by 2050
food
crisis
Source: Dery et al. 2007
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3. Reuse and Safe Discharge Options
12.3
14.1
3.0 – 5.3
Composition of Household Wastewater
3.6
0.8
50
0.7-1.2
500
Source: GTZ, adapted from R. Gensch
Agricultural Aspects of Sustainable Sanitation & Water Management
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3. Reuse or Safe Discharge Options
Productive, Reuse-Oriented Sanitation Systems
• Should allow for almost complete recovery of nutrients
• Should minimise the consumption and pollution of water resource
• Should support the conservation of soil structure
• Should support agricultural productivity
• Favour no specific technology
• Comprise decentralised and locally adapted as well as large-scale centralised
solutions
• Range from low cost basic sanitation to high-end solutions
Agricultural Aspects of Sustainable Sanitation & Water Management
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3. Reuse and Safe Discharge Options
Flowstreams
Excreta (urine and faeces):
• Nutrient content depends on the diet
• Contains all essential micronutrients
• Average amount of plant available
macronutrients:
o 4.5 kg/p/a Nitrogen
o 0.6 kg/p/a Phosphorus
o 1.2 kg/p/a Potassium (Jönnson et al. 2004)
• Most plant nutrients are found in urine
• combined application of faeces and urine
often advantageous
Application of urine with watering can in
Cagayan de Oro, Philippines Source: R. Gensch
Agricultural Aspects of Sustainable Sanitation & Water Management
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3. Reuse and Safe Discharge Options
Flowstreams
Greywater:
•Contains a low nutrient level compared with excreta
•High amount of slightly contaminated water
•After appropriate treatment greywater can be safely used for domestic or
irrigation purposes
Organic solid waste
•High share of organic matter
•Has to be decomposed or at least partly mineralised for effective reuse in
agriculture
Rainwater
•Not or only slightly contaminated
•Can be easily used for agricultural irrigation and for most household purposes
Agricultural Aspects of Sustainable Sanitation & Water Management
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3. Reuse and Safe Discharge Options
Reuse/Recharge Options
• Use of urine in agriculture
• Use of dehydrated faeces in agriculture
• Use of humus (incl. compost, vermicompost, terra preta, ecohumus)
• Use of biogas for cooking, lighting, heating
• Aquaculture
• Safe discharge of pretreated wastewater
• Fertilizer derived from urine products (struvite)
• Hydroponics
• Fertigation and irrigation
• Greywater towers
• Vertical gardens
• Leach fields, soak pits
• …
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3. Reuse and Safe Discharge Options
Reuse/Recharge Options
Farmer in Burkina Faso with onions
that are fertilized with urine (left)
and without urine (right) Source: L. Dagerskog
Agricultural Aspects of Sustainable Sanitation & Water Management
Sweet Corn produced with urine from
UDDT, Cagayan de Oro, Philippines
Source: R. Gensch
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3. Reuse and Safe Discharge Options
Reuse/Recharge Options
Women cooking with
biogas, Gorkha, Nepal
source: Practical Action, Rajesh KC
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3. Reuse and Safe Discharge Options
Reuse/Recharge Options
Wastewater-fed aquaculture in Lima, Peru,
Agricultural Aspects of Sustainable Sanitation & Water Management
source: P. EDWARDS
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3. Reuse and Safe Discharge Options
Reuse/Recharge Options
Leach field pipes Source: G Mauk
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3. Reuse and Safe Discharge Options
Reuse/Recharge Options
Construction of a Greywater Tower in Arba Minch Town,
Ethiopia Source: W. Shewa
Agricultural Aspects of Sustainable Sanitation & Water Management
Greywater directly poured into
the bag Source: W. Shewa
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4. Health Considerations
Multi Barrier Approach
•
WHO recognizes the potential of using excreta
in agriculture
•
Promotes a flexible multi-barrier approach for
managing the health risks
•
Series of measures/barriers along the entire
sanitation system from ‘toilet to table’
•
Each of the barriers has a certain potential to
reduce health risks associated with the
excreta use
•
Recommended to put in place several of these
barriers (if needed) in order to reduce the
health risk to an acceptable minimum
Source: WHO, FAO, UNEP
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4. Health Considerations
Multi Barrier Approach (for Urine Reuse)
Source: R. Gensch
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5. Benefits
•
Minimises negative impact on surface and
groundwater
•
Increase in agricultural yields especially if
directly compared with unfertilised crops
•
Comparable results as synthetic fertilisers
•
Reuse of organic matter improve the water
retention capacity, reduces vulnerability to
droughts, moderates soil temperature and
enhances the buffering capacity of the soil
•
help reduce health costs due to a better
nutritional status and improved sanitation
practices
Sweet Corn (cobs and young plants with
different urine application levels
Source: P. Morgan
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5. Benefits
•
Increase in yield improves availability,
affordability, access to food and has an
impact on the household income
•
Low cost fertiliser alternative
•
Farmers would require less expensive
commercial fertilisers
•
Value of the agricultural utilisable nutrients
produced by each human being can be seen
as a considerable quantity within the
national economy
Recent estimations vary between 4 € and 7
€ per person and year (KfW 2008) & (Stravato & Dagerskog 2008)
•
Sweet Corn (cobs and young plants with
different urine application levels
Source: P. Morgan
Agricultural Aspects of Sustainable Sanitation & Water Management
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5. Benefits
Monetary value of excreta
Source: R. Gensch
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6. References
BROWN, L. (2006): Plan B 2.0 – Rescuing a Planet under Stress & a Civilisation in Trouble. Updated & Expanded. Earth
Policy Institute, W.W. Norton & Company, New York, 266 p.
JOENSSON, H., RICHERT, A., VINNERAS, B>, SALOMON, E. (2004): Guidelines on the use of urine & faeces in crop
production. Report 2004–2. EcoSanRes Publications Series. SEI, Sweden, 35 p.
KFW (2008): Financial and Economic Assessment of Sanitation – Discussion Paper for the SuSanA working group on cost
and economics of sustainable sanitation
Smit J. (2000): Urban agriculture and biodiversity, Urban Agriculture Magazine; 1(1): 11-12. In: Esrey, S. A. (2000):
Towards a Recycling Society Ecological Sanitation - Closing the Loop to Food Security. ecosan - closing the loop in
wastewater management and sanitation. Proceedings of the International Symposium, 30-31 October 2000, Bonn,
Germany.
STRAVATO, L. & DAGERSKOG, L. (2008): Economic value of urine in Mauretania. Taken from presentation: IFAD’s
initiative on best practises optimising nutrient recycling. 5th SuSanA meeting Durban. February 16th - 17th 2008
UNEP (2002): Melbourne principles for sustainable cities. Integrated Management Series No. 1, UN Environmental
Programme, Division of Technology, Industry & Economics, Osaka
WHO/FAO/UNEP (2006): Guidelines for the safe use of wastewater, excreta and greywater. Geneva, Switzerland, World
Health Organization - WHO-FAO-UNEP, ISBN 9241546832
WWI (2005): World Watch Report - State of the World 2005. Redefining Global Security. World Watch Institute, World
Watch Books, ISBN: 0-393-32666-7, 237 p.
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