An electrochemical–biological hybrid system meets wastewater – Nature

Report on an Integrated Electrochemical-Biological System for Sustainable Development

Executive Summary

This report details an integrated system combining carbon dioxide (CO₂) electrolysis with biological denitrification. This hybrid technology presents a novel approach to simultaneously address carbon utilization and wastewater treatment. By converting CO₂ into formate, which is then used as a carbon source for denitrification, the system directly supports the achievement of multiple United Nations Sustainable Development Goals (SDGs), particularly those related to clean water, climate action, and sustainable innovation.

Technological Framework and Process

System Description

The core of the technology is an electrochemical-biological hybrid system that operates through a two-stage process:

1. Electrochemical CO₂ Reduction: Carbon dioxide is electrochemically reduced to produce formate (HCOO^–). This stage effectively captures and converts a greenhouse gas into a usable chemical product.
2. Biological Denitrification: The formate produced in the first stage is directly supplied to a bioreactor, where it serves as an electron donor and carbon source for denitrifying bacteria. These microorganisms then treat wastewater by converting harmful nitrates (NO₃^–) into harmless nitrogen gas (N₂).

Alignment with Sustainable Development Goals (SDGs)

Primary Contribution to SDG 6: Clean Water and Sanitation

The system makes a significant contribution to SDG 6 by enhancing wastewater treatment capabilities. Its primary function in this context is biological denitrification, a critical process for:

• Removing nitrates and nitrites from municipal and industrial wastewater.
• Preventing eutrophication of receiving water bodies.
• Improving overall water quality and ensuring safe water reuse.

Primary Contribution to SDG 13: Climate Action

The technology directly addresses SDG 13 by implementing a carbon capture and utilization (CCU) strategy. Key impacts include:

• Utilizing CO₂, a primary greenhouse gas, as a raw material.
• Converting atmospheric or industrial CO₂ into a value-added product (formate), thereby creating a carbon-negative or carbon-neutral process loop.
• Reducing the carbon footprint associated with conventional wastewater treatment, which often relies on external carbon sources derived from fossil fuels.

Contributions to Additional SDGs

The integrated nature of this system also supports other interconnected goals:

• SDG 9: Industry, Innovation, and Infrastructure: The hybrid system represents a significant technological innovation, promoting the development of sustainable and resilient infrastructure for waste and water management.
• SDG 11: Sustainable Cities and Communities: By providing a more efficient and environmentally friendly method for wastewater treatment, this technology helps cities manage resources more sustainably.
• SDG 12: Responsible Consumption and Production: The process exemplifies circular economy principles by transforming a waste stream (CO₂) into a valuable input for another essential process (denitrification), promoting sustainable production patterns.

Analysis of Sustainable Development Goals (SDGs) in the Article

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

The article discusses an integrated technology that combines carbon utilization with wastewater treatment. Based on this, the following SDGs are addressed:

• SDG 6: Clean Water and Sanitation: The core function of the technology is “wastewater treatment” through “biological denitrification,” which directly relates to improving water quality and sanitation.
• SDG 9: Industry, Innovation, and Infrastructure: The article describes a novel “integrated approach” combining “CO2 electrolysis with biological denitrification.” This represents an innovative and environmentally sound technology aimed at making industrial processes (like wastewater management) more sustainable.
• SDG 12: Responsible Consumption and Production: The system promotes a circular economy approach by utilizing a waste product (CO2) as a resource (“carbon source”) to treat another waste stream (wastewater). This aligns with goals to reduce waste and use resources more efficiently.
• SDG 13: Climate Action: The technology involves the “electrochemical reduction of CO2” and “carbon utilization.” This is a direct climate change mitigation strategy, as it captures and repurposes carbon dioxide, a primary greenhouse gas.

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

The article’s content points to several specific SDG targets:

1. Target 6.3: “By 2030, improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.” The described process of “wastewater denitrification” is a direct method for improving water quality by removing nitrogen pollutants.
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 industrial processes…” The “electrochemical–biological hybrid system” is an example of a clean and environmentally sound technology designed to make wastewater treatment more sustainable and resource-efficient.
3. Target 12.5: “By 2030, substantially reduce waste generation through prevention, reduction, recycling and reuse.” The system exemplifies this target by reusing captured CO2 (“carbon utilization”) and treating wastewater, effectively reducing two forms of waste/pollution simultaneously.
4. Target 13.2: “Integrate climate change measures into national policies, strategies and planning.” The technology for “electrochemical reduction of CO2” is a tangible climate change mitigation measure that can be implemented to reduce greenhouse gas levels.

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

While the article does not mention official SDG indicators, it implies several metrics that could be used to measure progress:

• For Target 6.3: The process of “biological denitrification” implies an indicator such as the percentage of nitrogen/nitrate removal from wastewater. This would measure the improvement in water quality and contribute to the official indicator 6.3.1 (Proportion of wastewater safely treated).
• For Target 9.4: The “electrochemical reduction of CO2” to produce formate implies an indicator related to technological efficiency, such as the rate of CO2 conversion or the amount of CO2 utilized per unit of energy consumed. This reflects the adoption of a more resource-efficient and clean technology.
• For Target 12.5 & 13.2: The concept of “carbon utilization” directly implies an indicator measuring the volume or mass of CO2 captured and repurposed. This metric would quantify both the reduction in waste (CO2 as a pollutant) and the direct impact on climate change mitigation.

4. Summary Table of SDGs, Targets, and Indicators

Source: nature.com