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United Nations Environment Programme

Facts about wastewater and nutrient management

Torsten Mandal

Wastewater and nutrient management for #ClimateAction

To solve the climate crisis we must take wastewater and nutrient management seriously. Recovered energy, water and nutrients can be used to help solve environmental and climate challenges.

 

 

Today wastewater treatment processes contribute as much to global GHG emissions as the global aviation industry. Whilst the full scale of GHG emissions from wastewater is still not clear, emissions from domestic wastewater increased 400% between 2000-2014. If efforts to reach SDG 6.3 (halving the proportion of untreaded wastewater) rely on conventional, linear treatment processes, these figures will increase considerably in the next few years.

Globally we produce 5x more wastewater than passes over the Niagara Falls every year. This volume continues to increase and pollution from unmanaged wastewater is still one of the most pressing global challenges. Excess nutrients flow into ecosystems harming their health and function, threatening human health and exacerbating climate change.

Rather than seeing wastewater as an ever-growing and costly problem, it should be looked to as a solution. It is a source for recovering valuable resources – not only recycled water but also energy and nutrients.

Wastewater has the potential to provide:

  • Electricity to half a billion people each year.
  • Nitrogen, Phosphorus and Potassium fertilizer that could offset 13% of the global fertilizer demand in agriculture.

This potential is not being realised. Only 11% of treated wastewater is currently being reused.

EXPLORE: Video on Wastewater and nutrient management for #ClimateAction

Read report: Wastewater: from problem to solution

In Chemicals & pollution action

Where does wastewater fit within the climate agenda?

The issue of wastewater is still invisible in the climate agenda and yet it is an issue that risks undermining progress towards climate commitments if it is not actively and urgently brought into considerations.

Dig deep enough and the elements are there. The significance of the water agenda for solving the climate challenge was clearly acknowledged at COP27 and reiterated at the UN 2023 Water conference. Sustainable wastewater management that recovers vital resources can contribute to climate mitigation as well as adaptation and resilience.

Addressing wastewater is not only a vital part of the water-climate nexus, but also connects across the sustainable development and biodiversity agenda.

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Energy recovery - with the potential to provide electricity to half a billion people

Whilst conventional wastewater treatment processes are energy intensive and are estimated to account for 3% of global electricity consumption, there is about five times more energy in wastewater than is needed to treat it. This energy is in the form of heat and from the chemical breakdown of the organic matter.

Biogas can be produced from the methane, so it can be captured, rather than being emitted, and contribute to climate mitigation. Solid fuel briquettes can be made from faecal sludge and have been shown to have comparable calorific value to commercial charcoal briquettes.

Energy from wastewater can help to contribute to green energy requirements and climate mitigation through providing an alternative and reliable energy source. Costs and emissions of energy transmission and distribution are also reduced by providing a localised supply.

wastewater

Nutrient recovery - with the potential to offset 13% of the global agricultural fertilizer demand

Nutrients such as nitrogen, phosphorous, potassium and organic carbon are important fertilizers and soil improvers for crop production. All of these can be recovered from wastewater.

Returning nutrients recovered from wastewater to croplands can reduce the demand on synthetic fertilizers, offsetting around 13% of the global fertilizer demand in agriculture. In 2015, it was estimated that the recovery of nitrogen, phosphorus and potassium from wastewater could result in revenue generation of 13.5 billion USD based on maximum theoretical volumes of wastewater produced. Based on the increases in market price this could be as much as 30-40 billion USD in 2022 and open up new economic opportunities.

Nutrient recovery limits GHG emissions – including from powerful gases such as methane and nitrous oxide coming from the organic breakdown during wastewater treatment. Both are long-lived gases with, respectively more than 80 and XX times the warming power of CO2.

Recovering these nutrients also prevents them being lost to the environment, reducing pollution pressure on marine and freshwater ecosystem integrity, reducing biodiversity loss.

polluted water

Related Sustainable Development Goals

Goal 3

Goal 3: Good Health and Well-Being
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Goal 11

Goal 11: Sustainable Cities and Communities
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Goal 15

Goal 15: Life on Land
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