The building sector's contribution to global CO2 emissions requires innovative approaches to reduce its environmental impact. Mass timber offers a viable solution due to its lower global warming potential during production and its ability to temporarily store carbon. This storage not only reduces radiative forcing, but also removes carbon from the atmosphere and can help mitigate climate change. The inclusion of biogenic carbon flows in LCA is therefore essential to accurately assess the environmental performance of a mass timber building. However, European standards do not include this in their guidelines for conducting LCA of bio-based materials. A systematic review of LCA studies on mass timber buildings highlighted the low presence of biogenic carbon flows and found the need for an advisory decision tree framework for accounting for these flows. Through an applied case study of a recent mass timber building project in Rotterdam, this research itself demonstrated that prolonged storage periods of wood products in construction can lead to a negative Global Warming Potential (GWP) score, thus supporting the inclusion of biogenic carbon in LCA models. However, the variability of LCA methodologies makes it difficult to compare studies on bio- based materials. To address this, a harmonization process among standardization organizations is recommended. Therefore, the decision tree framework is intended as a first approach to guide practitioners on how to model biogenic carbon, emphasizing the importance of accounting for temporal storage and forest dynamics based on a GWP-bio value.

The Dutch government has published the circular economy goal, which aims to reduce 50% consumption of raw materials by 2030 and realize full circularity by 2050. The goal leads the promotion of the sustainability development, particularly, on improving the resilience of the self-sufficient material supply chain in the Dutch economy. As one of the largest raw material consumers, the construction sector has urgent demand on the solution towards building circularity, which mainly indicates as increasing the use of secondary materials, and reducing the demolition and construction waste. Accordingly, the municipality of Leiden takes the leading role of circular transition, and seeks for the practical solution in construction sector at the local scale.
The circular construction hub is brought out as an effective solution to the building material circularity transition. A series conceptual development and a few pilot projects in Utrecht and Amsterdam were established, the effectiveness is proved by the promising results of transportation reduction, and recycling rate improvement.
Regardless numbers of the studies on the building material flow analysis and the development of the hubs in various forms, limited discussion of practical information for local hubs’ development is provided, and little quantitative analysis of the implementation of the circular construction hub was conducted. Decision making for the intermediate steps in the transition towards building material circularity, therefore, has little referencing information.
Hence, this research proposes the main research question as: How will the circular construction hub support the transition of building material circularity in the cities of the Netherlands? In order to explore the formation and the influence of the circular construction hub in city with the case study of Leiden. The research firstly specifies the formation of the hub by desk research; then quantifies the urban mining potential and handling capacity of the hub by Material Flow Analysis (MFA); then the suitability analysis of the hub’s location is provided by the Geographical Information System (GIS) based on the transportation emission (CO2 eq kg).
The research aims to draw a comprehensive understanding on the metabolic characteristics of building material flows with implementation of the circular construction hub, and provide a referencing value for municipality’s decision making on developing the hub in city Leiden, and further development in the cities of the Netherlands.

Building construction is a material-intensive process known for depleting natural resources, mainly gravel and sand, used in concrete production. At the same time, building demolition generates large amounts of construction and demolition waste (CDW), primarily consisting of end-of-life (EOL) concrete, a significant waste flow occurring in Europe's construction sector. The potential to deal with waste management and the uprising demand for new concrete in construction lies within circular economy-based solutions applied throughout the building's lifecycle. Steering in this direction, the European Union is endorsing a circular economy strategy that aims to utilize EOL concrete derived from CDW to produce new concrete and thus minimize virgin material inputs. These efforts have not been translated to a uniform framework for Europe, where practices, regulations for waste management, and market acceptance for secondary raw materials differ among member countries. In this project, different types of pre-demolition audits, demolition, and waste processing methods for EOL concrete are compared, showcasing the status quo across the EU and the Dutch case study, which portrays innovations that can shape the future of concrete recycling. An integrated LCA and LCC framework is applied from the demolition stage to waste processing and the production of materials for new construction to capture potential environmental and economic benefits and drawbacks at the end-of-life stage (EOL) of the building. The results showcase the pivotal role of BIM-supported pre-demolition audits in combination with selective demolition with benefits that include lower quantity of generated waste allocated to treatment and more components available for reuse. Finally, LIBS, a quality assurance tool for recycled aggregates, shows great potential in supporting a market for secondary raw materials in Europe.

Growing depletion of natural resources and ever-intensifying pollution of the environment has heightened the awareness for changes in our life and living. As an alternative to the traditional take-make-use-dispose production model, Circular Economy (CE), which focuses on recovering and regenerating products and materials, has been gathering interest. In particular, its application to the construction industry, which is responsible for a high percentage of global carbon emissions and resource consumption, is of both need and significance.

In Taiwan, the construction industry has been highlighted for the government-initiated CE transition. However, as elsewhere in the world, the construction industry has been slow in embracing circular principles and strategies. Among the challenges is the lack of an assessment metrics for gauging CE performance. Existing schemes for assessing building circularity are few. In 2018, the Building Research Establishment Environmental Assessment Method (BREEAM) from the United Kingdom proposed a framework of circular indicators (BREEAM-C) on the basis of its original green building certification scheme (BREEAM-G).

This thesis is an in-depth analysis of BREEAM-C on its applicability and potential for adoption in Taiwan to assess building circularity and to promote circular construction. Methods applied include literature review, cross-case analysis and collecting expert opinions using semi-structured interviews.

The analysis involves scrutinising whether the indicators are rooted in CE principles, are realizable through circular strategies, cover well different impact areas, structural layers and life-cycle stages of buildings, and can recognise circular building practices implemented. The applicability of BREEAM-C in real-life contexts is further examined using two circular building projects, Venlo City Hall of the Netherlands and TaiSugar’s Circular Village of Taiwan. The cross-case analysis also serves to identify BREEAM-C’s strengths, inadequacies as well as room for improvement.

Results showed that BREEAM-C is applicable, practical and can be adopted for building circularity assessment in Taiwan though not without adaptation or localisation considering different concerns with respect to climate and safety. Green building rating schemes, which have been widely adopted in the past decades offer an excellent platform for developing equivalent assessment schemes for circular buildings. In particular, for practitioners and stakeholders in Taiwan, using its own green building certification system, Ecology, Energy saving, Waste reduction and Health, as the basis would make new building circularity assessment scheme to be introduced, accepted and followed easier, which in turn would facilitate the promotion of circular construction.

The Netherlands has faced rapidly increasing housing prices over the previous years. As a counter measure, the government is aiming to increase the construction of new houses from around 70 thousand annually to 100 thousand annually, to achieve 900 thousand new houses by 2030. At the same time the world is facing a climate crisis and the Netherlands has pledged to decrease its emissions by at least 50% in 2030 in respect to 1990. The country must therefore reduce the impact of new built houses to be able to build more while reducing the total emissions.
Currently most houses are built with reinforced concrete which is generally not seen as a sustainable construction method due to the carbon emissions related to cement production. Building houses with cross-laminated timber panels or lightweight steel frames are proposed alternatives with a lower expected carbon footprint. This study was set up to perform a life cycle assessment of a steel and a timber building to compare their impact and find out under which circumstances building with steel or timber is a more sustainable option. A case study was found of a timber building and a hypothetical alternative was designed with steel frames which were both studied under three scenarios. The scenarios represent the choices that could be made regarding material production and waste treatment, ordered from worst-case, to expected, to best-case scenario.
When including the climate impact of construction, the treatment of waste, end-of-life benefits and carbon storage, the timber building performed better than the steel building in every scenario regarding global warming. However, waste treatment, end-of-life benefits and carbon storage are all dependent on future processes and emissions happening after 2030. When only the construction is included, the steel building outperformed the timber variant in the expected and best-case scenario. For this reason, building more houses with lightweight steelframes produced with at least 50% recycled steel would be the most beneficial for the Netherlands to reach its 2030 climate goals. When taking a longer timespan into consideration, timber buildings are the preferred choice due to the carbon storage effect, as long as the forests are replanted sustainably.
Either alternative was found to be a better alternative than the current houses built with reinforced concrete. If all houses built before 2030 were made with the alternative production methods this could save at least 20 Megaton of CO2 emissions. Because the alternatives researched made efficient use of materials, no significant issues were found for the demand of wood or steel in the Netherlands. In fact, steel demand is likely to decrease due to the reduced need for reinforcement steel. Further improvement on both alternatives is possible by increasing the potential lifespan of the buildings and reducing the emissions related to energy use in the production of materials.
The outcomes of this study may influence decision making depending on the weight the Dutch government gives to its climate goals of 2030 versus its total impact on climate change. Constructing steelframe houses may reduce construction emissions by 4% compared to timber by 2030 but would result in 64% more emission in 2100 due to the missed-out carbon storage. In general, the construction industry can improve a lot by increased use of low-carbon alternatives such as lightweight recycled steel and biobased materials.

Converging and lasting global issues such as climate change, global warming, resource depletion, etc. have urged interest in science, technology and policy for systemic societal change. These aspects have led the policy makers in the Netherlands to gradually adopt a transition approach. Over the past few years there is an increase in the electricity production from renewable sources with wind turbines being the largest contributors. Currently there are six offshore wind farms off the coast in the Netherlands and three more are expected to up by 2023. At the end of 2015 there were roughly at least 2525 onshore wind turbines generating 3000 megawatts (MW) of electricity. By 2020, Netherlands intended to have an onshore wind capacity of 6000 MW. While a lot is already being done towards renewable energy transition, there still lacks focus on several aspects. Currently, in most of the sectors that are focusing on renewable energy transition particularly the wind energy systems, the focus is mostly on cost efficiency or conversion efficiency and there has been less attention to environmental impact due to extraction of resources. Thus, it is crucial to change the nature of these renewable energy transitions and resource consumption so that it becomes circular. Recycling of renewable energy systems like wind turbines is rising up the agendas of policymakers, researchers and industrialists. However, circular economy is more than just recycling, this raises a question: What is hindering the transition towards a circular economy for the wind energy sector? Thus, the main objective of the research was to identify major challenges and obstacles hindering circular transition alongside the ongoing energy transition for the wind energy sector. Firstly, an elaborate literature review was conducted to understand the growth of the wind energy sector and the current state of energy transition, followed by the possibility of a circular transition for the wind energy as well. For the circular transition to befall, an elaborate literature review was conducted on transition studies, with a major focus on sustainable transitions. Considering there does not exist a transition framework for a circular transition, the comprehensive ‘failures framework’ was considered the most feasible method to capture the challenges and obstacles hindering circular transition for the wind energy sector. Three cases, an onshore, an offshore and near the shore were selected from various parts of the Netherlands. Data was collected from each case on various challenges and obstacles for the circular transition for the wind energy sector. Data collection for these cases was primarily done by interviews. Several challenges and obstacles were identified in each phase of wind farm development from design to decommissioning phase for both onshore and offshore wind farms, which were categorized under twelve failures mentioned in the failure’s framework. Eleven out of twelve types of failures were identified in the design and development phase and ten out of twelve types of failures were identified in the construction phase. And of all the challenges and obstacles identified majority of them were categorized under directionality failure followed by institutional failure. However, no challenges and obstacles have been categorized under these two failures in operation & maintenance phase and decommissioning phase only because the cases taken into consideration have not reached these phases of development yet. But these failures can be speculated to occur in both operation phase and decommissioning phase.Although, all the identified challenges and obstacles may not be applicable to every case but, the framework of failures obtained from this research definitely serves as a foundation or the starting point to understand why there is reluctance to adopt circular transition for the wind energy sector and what challenges are hindering this transition.On the whole, this research gives an overview of challenges and obstacles hindering circular transition for each phase of wind farm development and for the wind energy sector in general. The research also highlights different circular aspects and their level of consideration during the construction of wind farms. Although the research does not focus on providing solutions to the identified challenges and obstacles hindering circular transition and focuses on just the wind energy sector, it definitely takes one step towards the nexus of energy transition and circular transition.