Redefining separate or integrated food waste and wastewater streams for 29 large cities – Nature

Report on Integrated Urban Biowaste Management for Sustainable Development

This report summarizes a study on the integration of solid food waste and wastewater treatment systems in urban environments. The research introduces the Urban Biowaste Flux (UBF) model, a novel tool designed to help cities transition towards more sustainable waste management practices in alignment with the United Nations Sustainable Development Goals (SDGs).

Advancing Sustainable Cities and Communities (SDG 11)

Current urban waste management paradigms often treat solid waste and wastewater in isolation, representing a missed opportunity for resource integration and synergy. This fragmented approach challenges the objectives of SDG 11 (Sustainable Cities and Communities) by creating inefficient and unsustainable infrastructure. The study proposes a holistic solution by diverting food waste into sewage streams for co-treatment.

The Urban Biowaste Flux (UBF) Model

To evaluate this integrated approach on a city-wide scale, the Urban Biowaste Flux (UBF) model was developed. This model serves as a critical tool for urban planners and policymakers aiming to build resilient and sustainable infrastructure.

• It integrates mechanistic bioprocesses with a life-cycle assessment framework.
• It quantifies key sustainability metrics, including material flows, energy consumption, operational costs, and greenhouse gas emissions.
• The model is adaptable, utilizing city-specific data on waste composition, treatment parameters, and local tariffs to provide tailored strategies.

Methodology and Global Application

The UBF model’s efficacy was first validated using comprehensive data from Hong Kong. Following validation, it was applied to 28 large cities worldwide to assess the global potential of integrated waste management in achieving key development goals.

Key Findings and Implications for the SDGs

The analysis yielded critical insights into the economic and environmental performance of integrated systems, directly informing strategies for SDG 12 (Responsible Consumption and Production) and SDG 13 (Climate Action).

1. Economic Viability: A direct linear relationship was identified between the moisture content of food waste and the net cost of treatment. The study established a key economic threshold: sewer integration becomes cost-effective when food waste moisture reaches approximately 50 kg per capita per year. This provides a clear financial metric for cities considering infrastructure investments aligned with SDG 9 (Industry, Innovation, and Infrastructure).
2. Climate Action (SDG 13): The report highlights a significant environmental benefit. Optimized integrated treatment strategies have the potential to reduce overall greenhouse gas emissions by up to 69% compared to conventional separate treatment systems. This finding offers a tangible pathway for cities to contribute to global climate mitigation targets.
3. Resource Efficiency (SDG 6 & SDG 7): By co-processing food waste and wastewater, cities can enhance resource recovery, turning waste streams into valuable resources like clean energy. This supports SDG 7 (Affordable and Clean Energy) and improves the overall efficiency of water and sanitation systems as outlined in SDG 6 (Clean Water and Sanitation).

Conclusion: A Tool for Sustainable Policy

The Urban Biowaste Flux model provides policymakers with a practical, data-driven tool for designing sustainable and context-specific waste management strategies. By enabling a comprehensive assessment of integrated systems, the UBF model empowers cities to move beyond siloed approaches and develop holistic solutions that advance multiple Sustainable Development Goals simultaneously, fostering the creation of truly sustainable urban environments.

Analysis of Sustainable Development Goals in the Article

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

1. SDG 6: Clean Water and Sanitation
   • The article discusses the treatment of “wastewater” and “sewage streams.” It proposes an integrated solution for managing urban biowaste that directly involves wastewater treatment processes, aiming for a more holistic and efficient system. This connects to the goal of ensuring the availability and sustainable management of water and sanitation for all.
2. SDG 11: Sustainable Cities and Communities
   • The research is explicitly focused on “cities” and developing “sustainable and locale-specific waste management strategies.” The “urban biowaste flux model” is designed as a tool for policymakers in 28 large cities worldwide to manage solid waste and wastewater, directly addressing the challenge of making urban centers more sustainable and reducing their environmental impact.
3. SDG 12: Responsible Consumption and Production
   • The article centers on the management of “solid waste” and specifically “food waste.” It explores methods for resource integration and creating more efficient treatment systems, which aligns with the goal of ensuring sustainable consumption and production patterns by reducing waste generation.
4. SDG 13: Climate Action
   • A key component of the analysis is the quantification and reduction of “greenhouse gas emissions.” The article states that optimized treatment strategies could “cut overall emissions for targeted cities by up to 69%,” directly contributing to the goal of taking urgent action to combat climate change and its impacts.

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

1. Target 6.3: Improve water quality by 2030
   • 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 article’s focus on integrating food waste into “sewage streams” for treatment is a strategy to improve the overall management and treatment of wastewater, contributing to better water quality.
2. Target 11.6: Reduce the environmental impact of cities
   • 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 directly addresses this target by developing a model for “city-specific waste composition” and offering “sustainable and locale-specific waste management strategies” to handle solid waste and wastewater more effectively.
3. Target 12.5: Substantially reduce waste generation
   • By 2030, substantially reduce waste generation through prevention, reduction, recycling and reuse. The article’s approach of diverting “food waste” into sewage streams for integrated treatment represents a form of resource integration and recycling, turning a waste product into a resource within a holistic system, thereby contributing to the reduction of waste that would otherwise be managed separately.

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

1. Greenhouse Gas Emissions
   • The article explicitly quantifies “greenhouse gas emissions” and highlights that the proposed strategies could “cut overall emissions…by up to 69%.” This is a direct indicator for measuring progress on climate action (SDG 13) and reducing the environmental impact of cities (Target 11.6).
2. Net Costs and Cost-Effectiveness
   • The model evaluates the “net costs” of waste management and identifies a “moisture threshold…at which sewer integration becomes cost-effective.” This financial metric is a crucial indicator of the sustainability and feasibility of implementing new waste management strategies in cities (Target 11.6).
3. Material Flows and Energy Use
   • The “urban biowaste flux model” is designed for “quantifying material flows, energy use.” These metrics are essential for assessing the efficiency of resource integration and the overall environmental footprint of the waste management system, relevant to both Target 11.6 and Target 12.5.
4. Food Waste Moisture per Capita
   • The article identifies a specific threshold of “about 50 kg per capita per year” for food waste moisture. This serves as a practical, city-specific indicator for policymakers to determine the viability of adopting an integrated waste management approach, helping to tailor strategies to local conditions (Target 11.6).

4. Table of SDGs, Targets, and Indicators

Source: nature.com