The combined effects of growing populations, rising incomes and expanding cities will see demand for water rising exponentially, while supply becomes more erratic and uncertain due to climate change. Water scarcity already affects more than 40 percent of the global population, and with climate change, this is projected to rise.

This year's World Water Day, which was held last week, focused on wastewater. Wastewater is a valuable resource in the circular economy, and its safe management is an efficient investment in the health of humans and ecosystems. Treatment and re-use of wastewater to recover water and energy are becoming critical development and climate strategies for a number of countries.

Wastewater in the NDCs and Alignment with Sustainable Development Goals

In their national climate commitments for the Paris Agreement – known as nationally determined contributions (NDCs) – a number of countries included wastewater as a priority sector given the growing demand for sanitation and the large electricity costs and greenhouse gas (GHG) emissions associated with water supply and wastewater treatment.i Around 108 countries identified waste (including solid waste) as a priority sector in their mitigation component of the NDC. Wastewater-related mitigation action communicated in the NDCs includes three broad areas: energy production from wastewater, reducing methane emissions from wastewater and expansion of wastewater treatment plants.

Methane emissions from domestic and industrial wastewater disposal contributes about 9 percent of global anthropogenic methane sources. Around 64 INDCs included targets and actions that aim to reduce methane emissions from the waste sector (including solid waste). A number of developing countries—including Mauritius, Sudan and Tanzania—highlighted in their NDCs' mitigation sections efforts focused on recovering methane from wastewater using waste-to-energy technologies. These actions will be critical to achieving key targets as part of the Sustainable Development Goals (SDGs) – including Target 6.3, which focuses on reducing pollution, and Target 7.1, which aims to increase access to affordable, reliable and modern energy services.

Some countries have already begun capturing the methane using waste-to-energy technologies in an effort to reduce emissions. A WRI study of sludge-to-energy systems in Xiangyang, China found that this technology can yield economic savings, environmental benefits and renewable energy. One hundred additional Chinese cities are now scaling up organic waste-to-energy systems: By 2020, WRI estimates that China's waste-to-energy efforts will have reduced emissions by 20 million tons of CO2e.

In the adaptation sections of their NDCs, many countries have expressed that their primary concern is related to water.1 Very few countries explicitly use "wastewater" in specifying actions, but many communicated a number of water actions that are relevant for wastewater, such as improving water quality, water infrastructure and sanitation. More effective recycling and reuse of wastewater could provide important new water supplies for agriculture, industry and even drinking, particularly in places where climate change will increase drought and water stress (demand relative to available supply). Cabo Verde is one of the few countries that has covered sanitation and wastewater well in its NDC, highlighting a focus on construction of wastewater plants and expansion of public sewage collection systems and proper disposal. Morocco also included wastewater goals, which aim to connect all urban households to sewers, reach 100 percent wastewater treatment by 2030, and reuse 50 percent of wastewater by 2020.

Wastewater in the 2030 Agenda for Sustainable Development

Due to a lack of robust wastewater treatment infrastructure, more than 80 percent of the world's wastewater is flowing back into rivers, lakes and aquifers without being treated. This has resulted in 1.8 billion people using a source of drinking water contaminated with bacteria and pathogens, resulting serious health risks. SDG 6 covers the entire water cycle, including the management of water, wastewater and ecosystem resources. Wastewater is embedded under Target 6.3, with a focus on increasing treated wastewater, recycling and reuse globally.

WRI assessed the alignment of NDCs and SDGs found that actions communicated in 85 INDCs align with the targets under SDG 6.3, as well as a number of other goals and targets related to poverty, health, sustainable consumption and production, energy and sustainable cities.

Avoiding Trade-offs Will Be Critical in Aligning NDCs and SDGs Action Around Wastewater

As countries tackle wastewater, they need to pay attention to GHG emissions from fossil fuel-based wastewater treatment plants. A recent study highlighted that including carbon emissions from fossil-related carbon content of municipal and industrial wastewaters at various points in the treatment process may increase total global greenhouse gas emissions by 12 to 23 percent. In this case, countries need to identify clean energy sources, as well as look to circular waste-to-energy systems to power wastewater treatment plants, in order to avoid the trade-offs between improved water quality goals and climate targets for reducing CO2 emissions.

Developing and developed countries alike need to improve wastewater treatment to protect human health and ecosystems. Embedded in the bad news—that so little of the world's sewage and wastewater are being treated today—lies potentially good news: the opportunity to sustainably meet human and economic development goals while also reducing greenhouse gas emissions and helping countries achieve their NDCs.

1 An analysis by the French Water Partnership found that 106 of 129 (82%) of INDCs mentioned adaptation, and 92 percent of those included water as the priority adaptation concern, including droughts (and floods), agriculture/food security, and drinking water. Source: French Water Partnership, "REVIEW OF THE INTEGRATION OF WATER WITHIN THE INTENDED NATIONALLY DETERMINED CONTRIBUTIONS (INDCS) FOR COP21", accessed Mar. 22, 2017 at

i A 2012 World Bank study estimated electricity costs at 5% to 30% of the total operating cost of water and wastewater utilities, But the UN World Water Development Report (2014) cites other studies showing that in some developing countries such as India and Bangladesh, it is as high as 40% of the total operating cost (Van Den Berg and Danilenko, 2011, cited in UN WWDR 2014 report, pg. 63).