Urban Mining - Energy and resource savings due to urban mining
Starting point and Motivation
Urban mining aims to achieve efficient material recovery from (durable) goods at the end of their lifetime. Due to the enormous anthropogenic stocks that urban regions have built up over time, urban mining could make a significant contribution to increase the resource efficiency of cities – above all, for some materials the anthropogenic stocks are already in the range of economically mineable quantities of natural resources.
Contents and Objectives
The objectives of this project are to investigate energy and resource savings using anthropogenic stocks and to quantify potential urban mining concepts to increase resource efficiency based on three case studies. The case studies address different parts of the anthropogenic stock. Case study 1 deals with the efficient use and recovery of photovoltaic modules, case study 2 deals with the life cycle oriented management of underground infrastructure networks and case study 3 refers to the resource-efficient management of buildings at the end of their use phase. In addition to the case studies, stakeholder involvement is essential to the project to highlight potentials and challenges for urban mining on a general level based on expert knowledge and experience.
Various methods have been used to achieve the project objectives: i) review and critical analysis of existing studies on urban mining, ii) three case studies, which illustrate energy and resource savings through urban mining (using material flow analysis and life cycle assessment) for specific parts of the material stock in society, and iii) organized workshops and discussions with stakeholders to identify potentials for urban mining, current barriers and beneficial strategies.
The total anthropogenic material stock amounts to around 400 metric tons per capita, mostly consisting of mineral materials (concrete, bricks, sand and gravel). Although the size of anthropogenic stocks has been analysed in numerous studies, there is a lack of studies focusing on the actual recoverability of anthropogenic materials in terms of availability, accessibility, grade and composition.
Various external factors such as legislation, markets, and technologies determine the dynamic boundaries between resources (potentially recoverable materials) and reserves (actually recoverable materials under current conditions). The successful implementation of urban mining strategies is therefore a multi-disciplinary endeavour including legal, economic and technical factors. Thus, political incentives and societal awareness are as important as the promotion of topical research to fully exploit the potential of our urban mines.
- Photovoltaic modules will only become relevant as a waste stream for the recycling industry in 10 to 15 years due to steadily growing capacities in the past and their average useful lives of around 25 years. Nevertheless, there are many measures in different areas that need to be implemented in the near future in order to enable optimal PV recycling in Austria.
- Materials in underground infrastructures are associated with specific challenges and opportunities for urban mining due to their location. Interventions are typically associated with excavation activities, which often result in traffic restrictions and are associated with high costs (planning, implementation), especially in urban areas. Therefore, integrated and life cycle-oriented management of these infrastructures holds the potential to better utilize these materials (mainly copper and aluminium) as secondary raw materials, which results in ecological and economic benefits.
- Due to the large amount of recyclable materials in buildings, they are a significant source of potentially secondary raw materials, which should be further exploited. Concerning the management of end-of-life buildings, the renovation and further utilization of building parts as well as component reuse hold the highest potentials for energy and raw material savings. In general, detailed planning (including a recycling concept) of de-construction and its careful implementation are the basis for reuse or high-value recycling of building materials and therefore for the resource-efficient management of old buildings.
Outlook and Suggestions
The definition of the term "urban mining" is currently too vague and is also used ambiguously by experts. Therefore, the term should be used more concisely in general and with regard to public relations, it should include specifications on the research subjects and system boundaries of interest. Based on the present study, the following recommendations on the implementation of urban mining to increase resource efficiency can be given:
- Establish organisational structures that support networking of actors along the whole value chain (e.g. for buildings, photovoltaics and infrastructure).
- Develop databases, that characterize anthropogenic stocks in terms of type and quantity of raw materials including further information like spatial distribution (e.g. raw material cadastre).
- Develop concepts for modular design of buildings, for example to extend the useful life or reuse of individual modules.
- Develop and evaluate new business models for recycling and reuse of secondary raw materials.
- Develop methods to consider life cycle costs - especially to select best projects related to public tenders.
- Analyse different "Design-for-Recycling" concepts in terms of lifetime and impact on the operation and use phase (for example, through life cycle assessment).
Institute for Water Quality, Resource and Waste Management, TU Wien
Project or cooperation partners
Energieinstitut an der Johannes Kepler Universität Linz