A general procedure to identify indicators for evaluation and monitoring of nature-based solution projects.

In the last years, the idea of using natural elements or nature-based solutions (NbS) to mitigate the impacts of cities on climate, biodiversity and citizens' health became more popular in research and practice. Nevertheless, there are currently uncertainties in finding and selecting appropriate criteria and indicators for monitoring and evaluating the impact and performance of NbS and its co-creation processes. This paper proposes an easy-to-use and structured procedure for selecting appropriate criteria and indicators for monitoring and evaluating any kind of NbS project. The user is guided step by step in selecting meaningful metrics. The procedure is tested using a real case study from the Horizon 2020 research project CLEVER Cities as an example. The test shows that by following the indicated procedure, the criteria and indicator selection process is speeded up and reproducible.

Sustainability assessment of organic waste management in three EU Cities: Analysing stakeholder-based solutions.

This study focuses on a comprehensive sustainability assessment of the management of the organic fraction of municipal solid waste in Ghent (Belgium), Hamburg (Germany) and Pécs (Hungary). A sustainability assessment framework has been applied to analyse social, environmental, and economic consequences at the midpoint level (25 impact categories) and at the endpoint level (5 areas-of-protection). For each case study, the reference scenario was analysed, along with three solutions to improve the sustainability performance, which were selected and developed with the collaboration of local stakeholders. The solutions focus on food waste prevention, collection (increasing separate collection and household composting) and/or valorisation treatment (insect breeding, bioplastic production and improvement of centralised treatment). The results show that food waste prevention results in substantial improvements in all areas of protection when a significant quantity of food is saved. Solutions proposing innovative treatments such as insect breeding do not show clear improvements at the endpoint level, given current technology development level, but appear promising for some categories such as Revenues, Ecotoxicity, Land Use or Particulate Matter if the substituted products compensate the impact of the treatment (e.g., energy and water use). Enhancing the separate collection of organic waste can improve sustainability, but trade-offs may arise, e.g., decreased environmental savings from energy recovery at incineration. For this, the influence of the electricity mix (more or less decarbonised) should be carefully considered in future studies. The application of the solutions proposed to other cities should also consider potential bottlenecks such as legislation barriers, public acceptance, or management costs.