Eco-Friendly Green Roofs: Advancing Urban Sustainability Through Circular Economy Practices

The study highlights the integration of eco-friendly materials in green roof systems within a circular economy framework, emphasizing their potential to enhance urban sustainability and align with environmental goals. It calls for cohesive policies and ongoing research to fully realize these benefits.

Researchers from the Instituto Politecnico Nacional in Mexico and the Zurich University of Applied Sciences in Switzerland recently conducted comprehensive research exploring the integration of green roof systems within the framework of a circular economy (CE). The study focused on examining the reuse and recycling of alternative materials in green roof structures, aiming to assess their environmental impact and contribution to sustainable urban development. The data, collected from the Web of Science between 2012 and 2022, included 68 open-access articles from 24 countries, alongside a review of grey literature from the top five countries most active in this field.

Green Roofs: An Essential Urban Solution

The study emphasizes the ecological benefits of green roofs in urban environments, particularly their role in providing essential ecosystem services such as water retention, temperature regulation, and support for biodiversity. However, it also highlights the environmental dilemma posed by the polymeric components often used in green roof structures, which contribute to the carbon footprint. The review identifies significant advancements in the use of eco-friendly materials like rubber, biochar, and hydrogel, which are increasingly being incorporated into green roof substrates to enhance their environmental performance and align them with circular economy principles. Green roofs are recognized as nature-based solutions (NbSs) that play a critical role in urban green infrastructure (UGI), contributing to the Sustainable Development Goals (SDGs) by fostering sustainable cities and communities. Despite their potential, the review points out that the environmental impact of these alternative materials within the CE framework remains insufficiently explored. This gap in knowledge underscores the need for more comprehensive assessments of the long-term sustainability and environmental benefits of using such materials in green roof systems.

Policy Discrepancies and Urban Planning

The review also delves into the public policies of leading countries to understand how circular economy principles and green roof strategies are interconnected. It finds that while CE initiatives are generally implemented at the national level, green roof promotion tends to occur primarily at the city level. This discrepancy suggests a lack of integration between national CE policies and local urban planning strategies, which could hinder the broader adoption of green roofs as a standard element in sustainable urban development. The study advocates for more cohesive policy frameworks that incorporate green roofs into national CE strategies, thereby enhancing their potential to contribute to resource efficiency, waste reduction, and environmental sustainability.

Harnessing the Power of Alternative Materials

One of the key findings of the review is the prevalent use of alternative materials in the substrate layer of green roofs. Materials like biochar, rubber, and hydrogel are highlighted for their ability to improve water retention, nutrient availability, and overall substrate performance. By incorporating these materials, green roofs can significantly reduce their reliance on virgin resources and lower their environmental footprint, making them more sustainable in the long term. The review also discusses the potential of using recycled construction materials in green roofs, which can divert waste from landfills and contribute to a more circular economy. These materials not only offer environmental benefits but also enhance the functionality and longevity of green roof systems, further aligning them with CE principles.

The study underscores the importance of long-term environmental impact assessments, particularly concerning the quality of runoff water from green roofs that incorporate recycled or waste materials. This aspect is critical for ensuring that green roofs, while beneficial, do not inadvertently contribute to urban pollution or other environmental issues.

Towards a Sustainable Urban Future

The review highlights the significant potential of green roofs as vital components of sustainable urban infrastructure. By integrating CE principles into their design and implementation, green roofs can help cities adapt to climate change, improve resource efficiency, and promote environmental conservation. However, the study also emphasizes the need for ongoing research to fully understand the long-term environmental impacts of using alternative materials in green roof systems. Such research is essential to ensure that these practices not only contribute to the circular economy but also enhance the overall sustainability and resilience of urban environments. As cities continue to grow and face increasing environmental challenges, green roofs, when properly integrated into broader CE frameworks, can play a crucial role in creating healthier, more sustainable urban landscapes. This scoping review provides a foundation for future research and policy development, advocating for the expanded use of green roofs as a key strategy in the transition towards a circular and sustainable urban economy.