event 16 Nov 2016

Research // Wastewater As a Resource: The Water-Waste-Energy Nexus in Sub-Saharan Africa

By Paul Gremillion and Tamara Avellán. A Nexus Approach centred on wastewater treatment and recovery can link cycles of water, waste, and energy. Rich in carbon and nutrients, wastewater has the potential to supply greenhouse gas (GHG) neutral energy for households and irrigate and fertilise crops. Capturing the resources contained in wastewater can improve human and ecosystem health, reduce GHG emissions, and improve SSA’s food and energy security. (UNU-FLORES Policy Brief No. 1/2016)

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UNU-FLORES website, 4 pages, 310 kB


  • The population of Sub-Saharan Africa (SSA) is expected to double to 2.1 billion by 2050, mainly in urban and peri-urban areas. SSA relies overwhelmingly on solid fuels for household energy needs, causing deforestation and environmental degradation in many places.
  • Wastewater can provide a resource for irrigation, fertilisation, and energy: Humans produce about 12 m3 of water, 4.5 kg of nitrogen, and 0.6 kg of phosphorous per person per year. A community of 500 can irrigate about a hectare of agricultural land and fertilise five to seven hectares. Harvested plants from constructed wetlands for wastewater treatment can provide 12% of a village’s cooking fuel needs.
  • About 40% of the world’s croplands are in or within 20 km of cities. In SSA, less than 20% of these peri-urban lands are irrigated; most are supported only by rainfall. Application of treated wastewater provides the potential for expansion of peri-urban agriculture.
  • By applying the Nexus Approach resources can be linked to more than one use. This minimises losses of material and energy and maximises resource use impact, which can lead to sustainable development.




UNU-FLORES Institute for Integrated Management of Material Fluxes and of Resources

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