Agricultural Aspects of Sustainable Sanitation & Water Management 1 Robert Gensch, Xavier...

Agricultural Aspects of Sustainable Sanitation & Water Management 1

Agricultural Aspects of Sustainable Sanitation &

Water ManagementRobert Gensch, Xavier University

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



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Plant requirements

1. Background

Light

Carbon Dioxide

Soil Structur

e

Water

MacronutrientsNitrogen (N)Phosphorus (P) Potassium (K)Sulphur (S)Magnesium (Mg)Calcium (Ca)

Nutrients

MicronutrientsBoron (Bo)Copper (Cu)Iron (Fe)Chloride (Cl)Manganese (Mn)Molybdenum (Mo)Zinc (Zn)

Plant requirements Source: R. Gensch



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1. Background

Harvest(incl. nutrients & organic

matter)

Animal manureCompostHuman excretaFallow periods

Nutrient Flow Source: R. Gensch

Flow of Nutrients



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Agricultural Production in Former Times

1. Background

• 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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Nutrient Consumption and Excretion

1. Background

2.7 kg/a Nitrogen

0.4 kg/a Phosphorus

1.5 kg/a Potassium

2.7 kg/a Nitrogen

0.4 kg/a Phosphorus

1.5 kg/a Potassium

• Correlation between consumed nutrients and excreted nutrients

• About 99-100% of all consumed nutrients are excreted



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Closing the Loop

1. Background

Source: GTT, Photos: R. Gensch

NUTRIENTSNUTRIENTS

FOODFOOD



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Modern agricultural practises

1. Background

• 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



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1. Background

Source: R. Gensch

Harvest(incl. nutrients & organic

matter)

Animal manureCompostHuman excretaFallow periods

Synthetic fertiliser

AvailabilityAffordability

PolutionHealth Risks

Flow of Plant Nutrients



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Urbanisation

1. Background

• 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



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Urbanisation

1. Background

• Massive flow of nutrients

oFood from rural areas to cities

oNutrients (excreta): pits, lakes, waterbodies…

• But:

oNutrients and organic matter in excreta are toxic to different life forms living in water (sewage pollution)

oBiodiversity is threatened (Eutrophication)

oSoil fertility declines

Metro Manila Source: R. Gensch



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Soil Degradation


Map of Global Soil Degradation Source: FAO

Very high severity

High severity

Moderate severity

Low severity

Stable Land, Ice Caps or non-used wasteland

• The earth is losing 25 billion t/a of nutrient rich topsoil (WWI 2005)

• 2 billion ha of vegetated land degraded since 1945 (UNEP)



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Water Scarcity


Potable water being piped to a rice field, USA source: McCabe

• 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



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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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Limited Minable Fertilizer Resources


Source: J. Christiansen

• 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



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Phosphorus Peak


Peak phosphorus ‘Hubbert’ curve Source: Cordell, Drangert & WHite



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Phosphorus Peak


Phosphorus resources worldwide Source: A. Rosemarin et al



9.1 billion by 2050

food crisis

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Phosphorus Peak


Source: Dery et al. 2007



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Composition of Household Wastewater


50050

3.0

– 5.

3

0.7-

1.2

0.8

3.6

14.1

12.3

Source: GTZ, adapted from R. Gensch



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Productive, Reuse-Oriented Sanitation Systems

3. Reuse or Safe Discharge Options

• 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



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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



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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



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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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Sweet Corn produced with urine from UDDT, Cagayan de Oro, Philippines Source: R. Gensch

Farmer in Burkina Faso with onions that are fertilized with urine (left) and without urine (right) Source: L. Dagerskog



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Women cooking with biogas, Gorkha, Nepal source: Practical Action, Rajesh KC



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Wastewater-fed aquaculture in Lima, Peru, source: P. EDWARDS



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Leach field pipes Source: G Mauk



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Greywater directly poured into the bag Source: W. Shewa

Construction of a Greywater Tower in Arba Minch Town, Ethiopia Source: W. Shewa



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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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Multi Barrier Approach (for Urine Reuse)


Source: R. Gensch



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Sweet Corn (cobs and young plants with different urine application levelsSource: P. Morgan

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



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Sweet Corn (cobs and young plants with different urine application levelsSource: P. Morgan

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)



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Monetary value of excretaSource: R. Gensch

5. Benefits



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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.

Agricultural Aspects of Sustainable Sanitation & Water Management 36

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