The climate cost of cleaning water – WAMC

Climate Impact of U.S. Wastewater Treatment and Alignment with Sustainable Development Goals

Executive Summary

Wastewater treatment facilities in the United States, while essential for achieving Sustainable Development Goal 6 (Clean Water and Sanitation), are a significant source of greenhouse gas emissions, directly impacting SDG 13 (Climate Action). A comprehensive analysis of over 15,000 U.S. facilities reveals that the process of cleaning trillions of gallons of water annually generates substantial climate costs, necessitating an integrated approach to balance sanitation services with environmental stewardship.

Analysis of Greenhouse Gas Emissions

A study conducted by researchers from Northwestern University and the University of Illinois Urbana-Champaign quantified the climate impact of the U.S. wastewater sector. Key findings include:

• Annual emissions are estimated to be the equivalent of over 50 million tons of carbon dioxide (CO2e).
• The majority of these emissions are not CO2 but are composed of more potent greenhouse gases, primarily methane (CH4) and nitrous oxide (N2O).
• Methane is released from leaks in anaerobic digesters, which are used to break down sewage sludge.
• Nitrous oxide is a byproduct of the nitrification-denitrification process, a standard method for removing excess nitrogen to prevent water pollution.

Implications for Sustainable Development Goals (SDGs)

The emissions from wastewater treatment create a complex challenge, highlighting the interconnectedness of various SDGs:

1. SDG 6: Clean Water and Sanitation: The primary function of these plants directly supports Target 6.3 by treating wastewater to improve ambient water quality. However, the associated emissions reveal a critical trade-off that must be managed to ensure sanitation systems are environmentally sustainable.
2. SDG 13: Climate Action: The sector’s emissions represent a significant obstacle to achieving national climate targets. Integrating climate change mitigation measures into the operation of this essential infrastructure is imperative for fulfilling Target 13.2.
3. SDG 11: Sustainable Cities and Communities: As a core component of urban infrastructure, the environmental performance of wastewater facilities is central to Target 11.6, which aims to reduce the adverse environmental impact of cities, particularly in waste management.
4. SDG 12: Responsible Consumption and Production: The processes generate waste products (excess nitrogen) and leak valuable resources (methane as potential biogas). This presents an opportunity to apply circular economy principles in line with Target 12.5 to reduce waste and create value-added products.

Recommendations for Mitigation and SDG Advancement

The study proposes actionable strategies to reduce emissions, thereby advancing multiple SDGs simultaneously. These recommendations focus on improving operational efficiency and adopting circular economy models:

• Infrastructure Integrity and Methane Capture: Systematically identifying and repairing methane leaks in anaerobic digesters is a critical first step. This directly supports SDG 13 by cutting potent greenhouse gas emissions and contributes to SDG 11 by improving the sustainability of municipal services.
• Nutrient Recovery and Reuse: Developing and implementing technologies to harvest nitrogen directly from wastewater for use in products like fertilizer. This strategy addresses several goals:
  • It reduces nitrous oxide emissions (SDG 13).
  • It creates a valuable product from a waste stream, promoting a circular economy (SDG 12).
  • It prevents nitrogen pollution in receiving water bodies, further enhancing water quality (SDG 6).

Conclusion

As the global population increases and access to sanitation expands, the environmental footprint of wastewater treatment will grow. Addressing the sector’s greenhouse gas emissions is not only a climate necessity under SDG 13 but also an opportunity to innovate and create more resilient and sustainable systems that advance goals for clean water (SDG 6), sustainable cities (SDG 11), and responsible production (SDG 12). A transition towards low-emission, resource-recovering wastewater treatment is essential for achieving the 2030 Agenda for Sustainable Development.

Analysis of Sustainable Development Goals in the Article

1. Which SDGs are addressed or connected to the issues highlighted in the article?

• SDG 6: Clean Water and Sanitation

  The entire article is centered on wastewater treatment, which is a core component of SDG 6. It discusses how “Wastewater treatment plants in the U.S. clean trillions of gallons of water each year” from sinks and toilets, directly addressing the management of water and sanitation.

• SDG 9: Industry, Innovation and Infrastructure

  The article focuses on a specific type of infrastructure: “more than 15,000 wastewater treatment facilities.” It also discusses innovation and industrial processes by suggesting ways to improve these facilities, such as “repairing leaks in anaerobic digesters and harvesting nitrogen directly from wastewater,” which points to upgrading infrastructure to make it more sustainable.

• SDG 11: Sustainable Cities and Communities

  Wastewater treatment is a critical municipal service essential for the functioning of cities and communities. The article discusses the environmental impact of these services on a national scale, which is directly related to managing the environmental footprint of urban areas.

• SDG 13: Climate Action

  The primary focus of the study presented in the article is “to understand the climate costs associated with all this cleaning.” It quantifies the greenhouse gas emissions (methane, nitrous oxide, and CO2 equivalents) from these plants and explicitly states that reducing these emissions is an “important necessity for reaching climate targets.”

2. What specific targets under those SDGs can be identified based on the article’s content?

1. Target 6.3: By 2030, improve water quality by reducing pollution… halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.

   The article directly addresses this target by discussing the process of cleaning “trillions of gallons of water” to be “rendered clean enough to return to the environment.” While the U.S. has a high rate of treatment, the article highlights the negative environmental side effects (emissions) of the treatment process itself, which is a dimension of water quality management.

2. Target 9.4: By 2030, upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies and processes…

   This target is reflected in the study’s suggestions “to reduce the emissions from wastewater treatment plants.” The proposed actions, such as “identifying and repairing leaks in anaerobic digesters” and “harvesting nitrogen directly from wastewater for use in products such as fertilizer,” are clear examples of upgrading infrastructure and adopting cleaner, more resource-efficient processes.

3. Target 11.6: By 2030, reduce the adverse per capita environmental impact of cities, including by paying special attention to air quality and municipal and other waste management.

   The article’s focus on the 50 million tons of CO2 equivalent emissions from wastewater plants is a direct measurement of the adverse environmental impact of municipal waste (sewage) management, a key service in cities.

4. Target 13.2: Integrate climate change measures into national policies, strategies and planning.

   The article concludes that reducing emissions from this sector is an “increasingly important necessity for reaching climate targets.” This implies that the management of wastewater infrastructure must be integrated into national climate action strategies and policies to achieve overall emission reduction goals.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

• Greenhouse Gas Emissions: The most direct indicator mentioned is the total emissions from the wastewater sector. The article quantifies this as “the equivalent of over 50 million tons of carbon dioxide each year.” This serves as a baseline indicator for measuring progress on climate action (SDG 13) and sustainable infrastructure (SDG 9).
• Specific Gas Emissions (Methane and Nitrous Oxide): The article explicitly states that “the majority of emissions are in the form of methane and nitrous oxide.” Tracking the reduction of these specific, potent greenhouse gases is a key indicator of the effectiveness of mitigation efforts, such as repairing leaks in anaerobic digesters (for methane) and improving nitrogen removal processes (for nitrous oxide).
• Volume of Wastewater Treated: The article mentions that plants “clean trillions of gallons of water each year.” While the U.S. already treats a high volume, this can be used as an indicator for SDG 6.3, especially when compared with the emissions produced per gallon, to measure the efficiency and sustainability of the treatment process.
• Nitrogen Recovery Rate: The suggestion to “harvesting nitrogen directly from wastewater for use in products such as fertilizer” implies a new indicator: the amount or percentage of nitrogen recovered. This would measure progress towards more sustainable, circular processes within the infrastructure (SDG 9.4).

4. Summary Table of SDGs, Targets, and Indicators

Source: wamc.org