Dear Colleagues,

The economy for the last 150 years has been based upon the take–make–use–dispose model that—as is known—results in the unresponsibile, uncontrolled extraction of resources for production and consumption, and no effective plans for waste reutilisation and economy regeneration.

In recent years, such a linear model of the economy has become a global concern and has been proven as causing a number of problems, mainly related to:

• Virgin materials being extracted beyond their replenishment capacities;
• Post-use commodities being often landfilled or being treated in inceneration plants, which has the consequence of valuable and scarce natural resources being extracted anew, and the original resources being lost for the manufacturing of new products;
• Unsafe, unsustainable waste-management practices leading to hazardous substances being emitted into the air, water and soil, and generating alarming environmental-pollution conditions;
• Product manufacturing and distribution being responsible for extensive energy use, emissions of greenhouse gases and other pollutants, thus, heavily damaging human health, resources, climate change and ecosystem quality.

All those aspects contribute to making the linear model of the economy totally unsustainable from an integrated, holistic perspective. This puts emphasis upon the urgent need for transitioning to a model of the economy that maximises circularity of resources, thus, generating environmental and socioeconomic benefits that are well documented in the literature and mainly derived from resource prevention.

In this context, the circular economy (CE) is increasingly attracting interest and attention from international science and policy communities, as it provides the eco-design and promotion of durable products that can be reused, repaired and remanufactured before being recycled. By doing so, the CE helps in maintaining products, components and materials at their highest levels of utility and value.

The CE differs from the former, linear economic model, as it is essentially based upon the two complementary features of slowing and closing the resource loops that are accomplished through five circular flows (i.e. share, repair, reuse, remanufacture and recycling), whilst maximising resource efficiency. In practice, through those flows, the CE minimises waste and excessive resource utilisation by turning goods at the end of their lifespans, as well as the wastes from their manufacturing and usage, into resources for the production of other commodities. Therefore, from a CE perspective, integrated strategies should be implemented:

• for preventing wastes being generated both from the technical and the biological cycles; and
• for managing and recovering, in more sustainable manners, the biomass and non-biomass wastes that are inevitably generated.

Under this perspective, affordable, effective and sustainable waste-management systems are essential for sustainable development, as they can contribute to reducing the jeopardisation of material and energy resources from enhanced globalisation and industrialisation.

Within this context, it is no surprise that waste valorisation through sustainable management scenarios is increasingly receiving attention and interest from researchers, producers, and decision and policy makers. It plays multiple key roles in the sustainability of a huge number of sectors, including agriculture and food production, buildings and bioenergy, and can favour the implementation of sustainable development paths in the urban and rural context.

For waste-management systems to be sustainable, the environmental, economic and social aspects need to be computed. Methodologies, such as Life Cycle Assessment (LCA) and Life Cycle Sustainability Assessment (LCSA), are very powerful tools to address trade-offs, both amongst life cycle stages and amongst different sustainability pillars.

In this context, the significant response to our previous Special Issue encouraged the Journal Editors to implement a second volume on this topic, aiming at contributing further to advance the literature and the knowledge on such a relevant field of research. The Guest Editors are confident that, along with the previous one, this second volume will make it possible to create a reliable and up-to-date picture of the state of the art of LCA and LCSA applications for waste-management systems in the context of circular economy and circular bioeconomy.

Dr. Carlo Ingrao
Dr. Alberto Bezama
Dr. Annarita Paiano
Prof. Dr. Jakob Hildebrandt
Prof. Dr. Claudia Arcidiacono
Guest Editors

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• sustainability
• circular economy
• circular bioeconomy
• resource recovery
• life cycle assessment
• life cycle sustainability assessment

Title: Life cycle sustainability assessment of nature-based solutions for greywater treatment and reuse integrated with rainwater harvesting for residential buildings

Abstract: Nature-based solutions (NbS) are environmental interventions to improve resilience in urban spaces, fighting problems arising from unsustainable urbanization, such as climate change, loss of biodiversity and degradation of ecosystem services. Although most studies are focused only on environmental Life Cycle Assessment (LCA), mainly when comparing different alternatives, studies that address the three dimensions of the Life cycle Sustainability Assessment (LCSA) related to the use of NbS for water reuse, are still scarce in the literature especially discussing scenarios in both Latin America and Europe. In this context, this study proposes a LCSA of NbS applied to greywater treatment and reuse integrated with rainwater harvesting, thus considering the environmental, economic, and social dimensions. Basically, we accessed different case studies in Brazil and Germany. In Brazil, a modified constructed wetland was evaluated – the EvaTAC system, which combines an anaerobic digestion chamber with a constructed wetland with horizontal subsurface flow. In Germany, a vertical flow constructed wetland was designed to attend workers of the railway project Stuttgart 21 who were temporally residing on the site. Results from LCA, Life Cycle Costing (LCC), and Social LCA (S-LCA) were reported through a multicriteria analysis. Our findings provided sufficient subsidies capable of demonstrating the benefits of using NbS for the urban water management, identifying scenarios more suitable than conventional systems. We conclude that the evaluation of different alternatives from the perspective of only one dimension is shown to be quite restricted, thus, when considering more dimensions, other benefits may emerge and influence the choice of alternatives.

Keywords: green and blue infrastructure; life cycle assessment; economic viability; social impact; water reuse