40% of the global population live in coastal cities. This figure is predicted to increase as
inland populations migrate to coastal areas. This is due to land availability steadily
decreasing due to several factors such as drought and increasing requisite cropland
stemming from growing populations and the growth of the biofuels market. Simultaneously,
sea level rise (SLR) means that further strain will be put on land availability in coastal areas.
It is important to have solutions prepared for this event. One such potential solution is the
use of Modular Floating Structures (MFS) as dynamic platforms for floating urbanisations. An
MFS consists of a floating substructure on top of which a superstructure (buildings) can be
built. While MFS technology is not currently used anywhere in the world the technical
feasibility and use case potential of MFS has been demonstrated in previous research.
However the environmental impacts of MFS technology had previously not been
investigated. A prospective life cycle assessment (LCA) of potential MFS substructure
designs was devised in order to quantify and compare the potential environmental impacts
and to find potential for optimisation of the environmental performance of the substructures.
A case study of Taranto, Italy, a city which has the potential for using MFS technology was
taken for this research. In the baseline case it was assumed that the substructures would
have to travel 1898 km across the sea throughout their lifetime. All cradle-to-grave life cycle
inputs were included, excepting cut-offs. Only two main materials were considered suitable
for use in substructure construction: steel and reinforced-concrete. However four designs
were deployed. Virgin steel (VS), recycled steel (RS), 35 MPa Portland concrete (35 PC)
and 50 MPa Portland concrete (50 PC). The concrete designs did not have equivalent
buoyancy to the steel designs given the default geometric dimensions so these dimensions
were altered considering several factors (bending moment, stress, second moments of area,
draft).
A holistic approach was taken and all impact categories were considered, however particular
attention was given to the impact categories of climate change and marine ecotoxicity. For
all designs the raw materials used and the transport across the ocean held the greatest
share of the impacts. In the concrete designs a surprising finding was that the stainless steel
rebars used in their design held a larger share of the impacts across the board. The 50 PC
design performed by far the best overall however due to issues with working with concrete of
higher strengths it is unclear if the 50 MPa Portland concrete can be easily applied to MFS
substructure construction in the present day. In terms of present-day usability and
environmental performance the two forerunning designs were the RS design and the 35 PC
design. Trade-offs were found between design choices. The RS design had significantly
lower CO₂-Eq emissions with 7,292 t compared to the 35 MPa concrete design, which had
9,770 t CO₂-Eq. However, the 35 MPa design had much lower marine ecotoxicity with 984 t
DCB-Eq, than the RS design 4,256 t DCB-Eq. This higher marine ecotoxicity for the RS
design was largely (63%) due to the local environmental impact of sacrificial zinc anodes
corroding into the sea. These are used as cathodic protection for the steel. Altering the
cathodic protection is a possibility for reducing the marine ecotoxicity impacts of the steel
designs.
Normalisation and even weighting were applied to compare the overall impacts of the
designs. When total oceanic transport distance of the substructures is 482 km, in terms of
overall environmental impacts the 35 PC design outperforms the RS design by 22%. At 1898
km this decreases to 3%. At longer distances the RS design performs better due to its lighter
mass and subsequent lower impacts from oceanic transport. At 2467 km the RS design
outperforms the 35 PC design by 2%.
In the context of the EU, the legislation surrounding deconstruction of end of life (EoL) ships
and offshore installations is a key factor to consider. For offshore instalments which are to be
recycled, the deconstruction can only take place in a limited number of shipbreaking yards.
This directly affects the distance which the substructures must travel across the sea. And
this is a main influencing factor which can lead to MFS substructure optimisation, in terms of
environmental impacts.
Finally, environmental impacts are not the only considerations important to design choice.
Other factors should be considered, namely the material availability in a given region and the
disparity in recyclability between steel and concrete. Further research can develop these
findings and investigate other highlighted potential concrete reinforcement material options
such as epoxy coated steel and plastic fibre reinforcements. Furthermore, this research can
be used as a building block for comparing the environmental impacts of MFS technology to
coastal urban expansion alternatives such as land reclamation.

The construction sector, known for its extensive use of building materials, significantly contributes to environmental degradation, resource depletion, and waste management challenges. While much attention has been given to creating circular systems in demolition, renovation processes—occurring more frequently due to varying lifespans of building elements—remain underexplored. Understanding the material output from renovation projects across different building types and their potential for reuse and recycling is crucial.
This thesis introduces a novel approach to calculating renovation and transformation waste, drawing on existing literature related to skip use for material intensity (MI) calculations for demolition and waste quantification. Renovations are defined as improving a building to enhance the physical conditions and functional performance. Transformations are similar to renovations but include a change of use of the building. Data on renovation and transformation projects were acquired to calculate the amount of waste generated as well as the renovation and transformation material intensities (r,tMIs) of different building types and for different construction years. The r,tMIs were calculated by dividing the mass of each material per project by the floor area of that project. The r,tMIs were then grouped by building type and construction year. The materials examined include Undifferentiated, Gypsum, Wood, Synthetic material, Paper/cardboard, and Aggregates. The building types are classified as detached houses, row houses, apartments, educational buildings, health facilities, offices, and ‘other’, with construction years grouped into Before-1945, 1945-1970, 1970-2000, 2000 and later, and Year unknown. The 358 projects are dispersed across the Netherlands and took place between January 2021 and May 2024.
It was found that the Undifferentiated waste stream constitutes a large portion of both renovation and transformation waste. Among renovation projects, apartments represent a significant portion, while transformation projects are limited to educational buildings, offices, and ‘other’ categories. Transformation projects tend to have higher tMI values compared to renovation rMIs. Undifferentiated and Aggregates are consistently present across all building types, whereas Gypsum and Synthetic materials are less common in number and mass. Additionally, a trend of decreasing tMI values for newer buildings was observed in transformation projects, a pattern not evident in renovation projects.
These insights lay the groundwork for a deeper understanding of material flows in renovation and transformation practices, serving as a strong foundation for future research. The findings can be used by renovation companies and contractors to estimate the amount of renovation waste from future projects by multiplying the r,tMIs with the specific floor area of that project. The findings can also be used by waste treatment companies to increase the efficiency of waste collection, transport, and treatment.

GIS bottom-up analysis of the material stock of construction materials (concrete, bricks, mortar) in buildings in Brno, Czech Republic.

Concrete is one of the most widely used materials in residential building construction. It contributes about 4% to 7% of global greenhouse gas emissions annually. Thus, better understanding the material stocks and flows of concrete can support efforts to better manage this resource and its use. Concrete is especially popular for the construction of building foundations. Previous research has shown that foundations can account for 25% to 60% of residential housing mass. Despite this, no in-depth analysis of material requirements of foundations has been conducted. Foundation design depends on the housing type and soil type. Considering foundations’ substantial share of building mass, I analyze them in this thesis in the form of a case study of residential housing built in Trondheim between 2010 and 2020. To account for all emissions from cradle-to-construction site I also compare the concrete production emissions to the last-leg transport emissions. The residential building foundations’ material requirements were estimated with a model I specifically developed for this thesis. 507 000 tonnes of concrete were used from 2010 to 2020 to build residential building foundations in Trondheim. The results show that the concrete production emissions represent 99% and the last-leg transport emissions 1% of the total cradle-to-construction site emissions. The average material intensity coefficient across all buildings in Trondheim is 402 kg of concrete in the foundation per one m2 useful floor area. I disaggregated the buildings into five types: single family house, semi-detached house, rowhouse, apartment building, assisted & communal living. When disaggregated, the building types’ material intensities vary, on average, 8% around 402 kg/m2 useful floor area. The largest difference being 20% below the mean. As a result, there are no substantial differences of material requirements per m2 useful floor area between different building types. However, building on peat and bog soils increases the material requirements by 80% compared to all other soil types found in Trondheim. This is due to the low bearing capacity of peat and bog soils. Trondheim currently plans its residential zoning until 2034. 5% of the planned zones are located on peat and bog. A rough estimate suggests that up to 380 000 tonnes of carbon could be stored in the affected peat and bog areas, which could be released as construction on this land begins. Together with the 80% increased material requirements of foundations on peat and bog, this can cause a lot of emissions. As a result, my short-term recommendation is that these areas are either preserved as nature reserves or only light structures that do not need a foundation are constructed. In the long-term I recommend that new zoning types for city planning are developed that take soil types into account. Lastly, the effects of soil types should be taken into account in future studies of the material stock in residential housing. Feel free to contact the author for more information and the supporting information.

This research delves into the challenging task of exploring secondary materials supply from existing building stocks, crucial for sustainable resource management in the face of climate change. Focused on Hamburg, Germany, the study employs a unique combination of GIS-based bottom-up building stock analysis and dynamic Material Flow Analysis (dMFA) at the individual building level. Unlike previous studies, this approach specifically explores the dynamics of single buildings based on their unique characteristics, such as function and building age. The research explores the question of to what extent Hamburg’s construction sector can meet its material demand for stock maintenance through secondary materials until 2075. The study emphasizes the often-overlooked impact of regional and local dynamics, making Hamburg an ideal case study. The city’s lack of policies regarding primary material consumption in construction adds relevance to the investigation. By addressing five sub-research questions, the study comprehensively examines current material stocks, future outflows caused by demolition and renovation, future inflows for maintenance of the building stock and replacement construction, and the secondary material potential of outflows. The methodology involves quantifying material masses through GIS analysis and the application of material intensities for different building types and age cohorts. The obtained results feed into the dynamic MFA model. Recommendations arising from the findings include preparing for efficient brick recycling, developing storage concepts for secondary materials based on the determined spatio-temporal characteristics of outflows and initiating policy discussions on reducing primary material consumption in construction. This research not only contributes to the field of Industrial Ecology by extending the methodology for material stock and flow research on the local level but also has practical implications. Stakeholders in Hamburg, including policymakers, urban planners, and waste operators, can leverage the developed methodologies and results for informed decision-making. The study provides a blueprint for future research in other urban regions, showcasing the potential of openly available cadastre data and emphasizing the importance of addressing the complexities of material flows at a granular level.

Modular Floating Structures (MFS) have emerged as an innovative alternative for sustainable offshore urban development, providing a response to the multifaceted challenges posed by coastal urban expansion: significant urban growth and coastal migration, increasing sea-level rise exposure and land scarcity. This thesis presents a geographically oriented exploration of the global technical and motivation potential of MFS – in maximum achievable suitable area, offshore population and material demand -, integrating technical, environmental, and demographic factors through a comprehensive GIS analysis. The methodology of this analysis involves the following key steps: 1) Establishing the Service Limit State (SLS) technical potential map by considering the natural constraints bathymetry, average wave energy, average wind speed, and hurricane risk; 2) establishing the Ultimate Limit State (ULS) technical potential map based on the SLS map and the extreme value constraints 100-year return significant wave height and 100-year return wind velocity; 3) establishing the ocean planning technical potential based on the ULS map and integrating the ocean planning constraints marine protected areas and shipping routes; 4) establishing the motivation potential maps, which are based on the outcomes of steps 1, 2, and 3 and the proximity to a coastal city as a key motivation factor; 5) evaluating additional motivation layers to reveal where potential driving forces are for floating urban development within local contexts. The maps lead to first estimates of maximum suitable area and offshore population, guiding calculations for required materials in floating breakwaters, proposed as reused end-of-life (EOL) ships, and MFS substructures. This thesis uncovers several insights. The use of Geographical Information Systems (GIS) in this field enables the exploration of the technical potential of offshore urban development, offering first estimations for total area, offshore population, and material use (specifically EOL ships and steel). On a global scale, about 84000 km2 are suitable for MFS implementation, potentially accommodating up to 1.6 billion people. These results demonstrate the potential to contribute significantly to climate-adaptive housing capacity. If the entire technical potential were to be realized the global demand for EOL ships would be approximately 261000, a demand significantly exceeding the current in-use global merchant fleet by nearly threefold. The global steel demand for the construction of the MFS substructures would be 26 billion tons, a vast amount that exceeds the annual global steel demand by about 20 times. These vast numbers may significantly impact the ship-breaking industry and global steel flows. These insights provide valuable perspectives on MFS implementation, holding the potential to significantly contribute to climate-adaptive housing capacity, however raising critical questions about sustainable material consumption and production. This research unfolds new possibilities in the field of sustainable offshore urban development and serves as a launchpad for further large scale exploration and analysis in this dynamic area of research. Future research could further assess the sustainability of offshore urban development, building upon the findings of this thesis. Potential areas of investigation include for example comparing material requirements for MFS substructures to those of land-based building substructures or conducting micro, meso or macro-scale scenario-based Material Flow Analysis (MFA) to evaluate the influence on the global steel flow and ship-breaking industry, using the technical potential estimates presented in this thesis on local and global scale as a foundational reference.

The growing world population gaining affluence is driving the extraction of raw materials. Resource availability is finite and concerns about future supply shortages rise. An approach to tackle this problem is circular economy which entails multiple strategies to reduce the demand of virgin materials. The implementation of those strategies require knowledge about material stocks and flows in a society. Material Flow Analysis can provide those insights. This fast developing field brought about MaTrace models which allow to trace the fate of materials in an open-loop recycling system. Recycling is only one of multiple circular strategies, thus the purpose of this research is to integrate an elaborate reuse model into a MaTrace model to build the foundation of a model which considers multiple circular strategies in sufficient ways.

Two existing models were combined to achieve this: Consumer goods present in the MaTrace model were redirected into a reuse model and the end of life products of the reuse model were fed back into the MaTrace model. The impacts of this model extension were investigated by comparing the total in-use stock when considering one, two, and three consumer products' use cycles. Furthermore, Monte Carlo simulations were conducted to gain an understanding of the model behaviour.

The results show that the total in-use stock increases in the peak by 8 % when reuse is considered. However, the gross stock dynamics do not change significantly in comparison to the original model. The evaluation of the Monte Carlo simulations revealed that the input which contributes the most uncertainty to the total in-use stock is the split of the initial material inflow. Furthermore, the results of the Monte Carlo simulations appear to be strongly connected to the initial input data. On the basis of this research it can be recommended to further extend MaTrace models to obtain a more comprehensive representation of a circular economy. Furthermore, MaTrace models using time series data for inflows and model parameter have to be created, this way MaTrace models can follow the evolution of MFA from static to dynamic models.

Transitioning of energy intensive industries (EIIs) towards more sustainability forms an important building block in achieving the Paris climate goals. Silicon carbide (SiC) production is such an EII, though it has not yet received much attention in systemic research. This thesis attempts to fill this gap by studying how SiC flows through the global economy. The objectives are to describe the SiC supply chain, quantify its flows and analyse the supply chain’s resilience. Findings: The global SiC production capacity constitutes 1 000 000 t per year. With 55.34% the Asia Pacific region is the biggest producer, followed by Europe with 32.7%, rest of world with 7.96% and North America with 4%. In order of quantity, abrasives, metallurgy, refractories, technical ceramics, other industrial uses, semiconductors and jewellery are the main applications of SiC. Around 5% of the material is recycled (USGS, 2021). High energy requirements in SiC production, as well as strict emission regulations are identified as the main supply risks. Substitution, use reduction, recycling and stockpiling can only minimally absorb supply disturbances at their current state. However, recycling is currently a popular topic in the industry and under development. In the mid-term, recycling activities might become a way to increase supply chain resilience. Another strategy that could lower pressure on the supply chain is using SiC production to balance the energy grid. That is, to produce when there is an oversupply of energy and to halt production when there is a shortcoming. Implications: This thesis shows that sustainability efforts in the SiC industry are not only environmentally desirable, but might also add to its supply chain’s resilience. The case of SiC shows that small EIIs that have so far not received much attention can offer high returns in terms of knowledge gained.

With growing demand for energy and the shift towards renewable energy, countries like India are targeting energy mixture with alternate sources like solar, wind and water. With the current growth of solar energy use in India, it is predicted that high amounts of Solar Photovoltaic (PV) waste would be generated in the near future which left improperly managed would lead high amount of useful and expensive material ending up in landfills. This research focuses on the potential material generated from the growth of solar PV stock in India.
This research studied the growth of solar PV industry and the spread of Solar PV growth in India. The stock growth of solar PV till 2030 based on India’s renewable energy goal of 280 GW solar energy is taken. Further study on End of Life (EOL) management of Solar PV was studied and the best practice scenarios from around the globe for handling Solar PV waste was studied. The circular economy approach for the Solar PV industry was also reviewed. 3 scenarios were created to determine how the waste from these Solar PV would be managed based on the current state in India, using best-case scenario from around the world and circular economy practices. These scenarios were simulated using dynamic material flow analysis to determine the waste inflow and outflow of material based on the defined scenario.
It was determined that more than 21 million tonnes of waste would end up in landfill by 2060 if India does not increase its recycling capabilities. Also, by adapting Germany’s WEEE regulation for solar PV waste management, 2 other scenarios are created, which uses extended producer responsibility and would provide India with the capability to handle future Solar PV waste. A comparison of these 2 scenarios showed higher recovery of material in one (423 thousand tonnes) while generating 21 times more waste to landfill than the other (16 thousand tonnes).
It is found that the outflow of tonnes of material is same in all 3 of the scenarios and the highest amount of waste produced by the 280GW target of 2030 would be in 2055 at over 1.6 million tonnes. It is predicted that landfill can end by 2033 or 2044 in the defined scenarios but shows variation in the amount of recovered material would differ between them. Achieving the scenarios put forward would involve coordination between Government agencies, producers of solar PV and the actual users of PVs. A shift to a formal waste management sector would be required and a successful implementation of policies and targets would lead to improvement in multiple Sustainable Development Goals (SDG) for India.