Agriculture is under significant pressure to meet current and future food demands. Food consumption growth and climate change push the system to produce more food with the same resources. Irrigation is a key strategy to producing higher yields but current practices are already consuming non-renewable water, threatening the natural and human ecosystem. Desalination – the conversion of saltwater from to freshwater – could help ease constraints on irrigation resources, eliminate unsustainable withdrawals and improve yields in a more difficult climate for food producers (for example in increasingly drier regions). However the extent to which desalination can be deployed, and its associated impacts at a global level is largely unquantified. Using data from 172 countries, We estimate the global demand for desalinated irrigation water in 2050 accounting for climate change and varying blue water availability. We assume this water is used to replace both unsustainably sourced freshwater and to meet irrigation requirements under climatic changes. We assess its cost, energy requirement and the brine produced (an environmental impact from desalination). Results indicate that desalinated water could sustainably feed an additional 500 million to 1 billion people when replacing unsustainable blue water withdrawals within the current system and up to 3.5-5 billion people when providing the water resources to close yield gaps. The annual cost of water is significantly higher than current irrigation at 160-2000 billion euros. The use of desalination at a global scale is unlikely due to prohibitive costs and energy requirements. The feasibility of desalination increases with future technological advancements, increasing water scarcity, decreasing costs, and renewable energy integration. However, challenges such as brine disposal and socio-economic constraints need to be solved. We anticipate that desalinated irrigation is looked at as a niche pathway to provide necessary water resources next to storage fed irrigation and irrigation water application efficiency improvements.

This research explores the intersection between circular economy strategies, critical raw materials (CRMs) and the defence sector, especially focusing on Neodymium-Iron-Boron (NdFeB) magnets. The significance of CRMs in modern defence applications and the associated risks of geopolitical and supply chain disruptions underscore the necessity for a secure supply. Circular strategies are crucial not only for securing a stable supply of CRMs but also for their potential to significantly reduce environmental impacts. This study aims to determine the effectiveness of various circular strategies in securing a stable supply of CRMs, thereby enhancing national security and promoting environmental sustainability. To address the research question, a mixed-methods approach was employed. Secondary data collection involved a review of scientific and grey literature, while primary data was obtained through interviews with experts. The conceptual framework was based on the 9R framework of circular strategies, chosen for its comprehensive coverage of all value retention options, from smarter product use and manufacturing, and lifespan-extending practices to the useful application of materials. This framework was adapted to the context of CRMs. The analysis was conducted using the backcasting method to develop strategic pathways for implementation. From the results, it is clear that NdFeB magnets are crucial to the defence sector due to their exceptional magnetic properties. This makes them indispensable in various defence applications, such as in motors, sensors, and communication devices. The reliance on CRMs like neodymium and dysprosium for the production of NdFeB magnets poses a significant risk due to their limited supply and geopolitical concentration. The study identified effective circular strategies on all 10 levels of value retention. This includes modular design, which facilitates easier disassembly and reuse, and advanced recycling techniques like hydrogen decrepitation, which efficiently reclaims materials. These strategies are already being implemented in the civil sector and can be adapted for defence applications to enhance sustainability and resource efficiency. To implement the circular strategies in the defence sector, barriers and enablers are highlighted on four levels: cultural, regulatory, market and technological challenges. Culturally, the defence sector has a somewhat conservative approach in which operational effectiveness is considered most important. Awareness about sustainability and CRMs can be created through programs, training and role modelling. Secondly, the defence sector is heavily regulated with stringent standards for performance and safety. Therefore, policies are important to ensure that circular practices comply with existing standards and incentives should be created. On the market level, commercial considerations are said to be the hardest challenges which should be taken care of in procurement processes. Lastly, adopting circular strategies involves technological innovations for which investments and development are crucial. Collaboration among various stakeholders is essential to the implementation. A detailed implementation plan is provided including measures to overcome the barriers alongside an indication of time. The research concludes that implementing circular strategies on NdFeB magnets within the defence should be improved as many more benefits can be gained from further implementation especially with regards to lowering dependence on CRMs. By adopting these strategies, the defence sector can not only secure a more reliable supply of critical materials but also contribute to broader sustainability goals. The circular strategies could be tailored to fit specifically into the defence sector by addressing unique challenges and leveraging opportunities.

The food system emits one third of anthropogenic greenhouse gas (GHG) emissions and is projected to contribute 0.9 °C to end-of-century warming. It is also a primary source of methane; a powerful short-lived climate forcer (SLCF) and the second-most important GHG. Most food system methane emissions result from livestock production and is biogenic (part of the short carbon cycle). As such, livestock emission reductions can actively lower surface temperatures. Despite this, the livestock sector’s current commitments do not meet the IPCC’s 2035 global emissions reduction target. Here, we use the reduced-complexity climate model MAGICC to show that reduction trajectories identified by expert-elicitation for a livestock sector compliant with the Paris Agreement would avoid up to 0.42 °C warming by 2100. Specifically, a reduction in methane emission contributes 76.6% to this cooling in 2050 (of a total of 0.17 °C). Climate studies typically report emissions using GWP100, which underestimates the warming potential of SLCFs in the short term. We assess various climate metrics’ performance relative to MAGICC outcomes, and find better performance for target-aligned time horizons (for both 1.5 °C and 2.0 °C). Our findings reinforce the scientific consensus that reductions in livestock emissions are unavoidable in meeting targets and developing climate policy.

Despite The Hague's historically mild climate, it is experiencing rising temperatures and more frequent heatwaves, resulting in a growing demand for space cooling. However, there is a significant gap in research and sustainable policies to address this demand in an environmentally and socially responsible manner. While studies have examined the environmental impacts of residential heating, cooling remains understudied, and The Hague lacks sustainable cooling policies. This study projects cooling demand, energy consumption, material usage, and greenhouse gas emissions in The Hague for the status quo (2020), 2030, and three 2050 scenarios. It uses geospatial analysis of residential and office buildings and uses a thermodynamic model to calculate cooling demand in a bottom-up approach, before evaluating the aggregate environmental impacts. Despite offices accounting for only 13% of floor space, they contribute to 34% of present-day cooling demand and 65% of associated greenhouse gas emissions. Currently, space cooling accounts for 25% of annual office electricity consumption and 5.5% of residential electricity use. Moreover, 77% of cooling demand remains unmet, particularly affecting economically disadvantaged neighborhoods. The results suggest that adopting stringent climate change adaptation measures may reduce cooling demand and environmental impacts, even in the face of a warming climate. However, a business-as-usual scenario predicts a doubling of cooling demand and a significant rise in associated environmental impacts, challenging the Netherlands' goal of achieving net-zero emissions by 2050. Sensitivity analyses highlight key areas for The Hague to focus on, including thermal comfort standards, addressing the urban heat island effect, and improving the energy efficiency of cooling technologies. The study further offers recommendations to mitigate environmental impacts, such as minimum energy label standards for building renovations and promoting circular economy practices for cooling equipment. In conclusion, this study underscores the need to address space cooling in The Hague and the Netherlands. Without action, environmental impacts will worsen the effects of climate change. To tackle this challenge, the study recommends prioritizing energy-efficient cooling technologies, utilizing synergies between sustainable heating and cooling, and incorporating environmental justice into policy measures. This is the path towards securing a sustainable and cooler future for The Hague.

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.

The built environment is responsible for a substantial amount of energy use and greenhouse gas emissions. To improve energy efficiency and reduce environmental impacts, buildings can be renovated or replaced with more energy-efficient alternatives. Although new buildings often cause less environmental impacts from operating energy use, the higher material requirements cause additional environmental impacts. Housing corporations own more than 25% of residences in the Netherlands and need to decide between different energy efficiency improvement methods for their building stock. Therefore, the proposed thesis has the following research question: What are optimal building renovation or replacement solutions for housing corporations to improve energy efficiency and reduce environmental impacts in the context of the Dutch climate goals? Environmental impacts of materials and energy have been calculated according to the MPG+ method, which follows the life cycle assessment approach. The results show that extensively renovated porch flats and new buildings lead to similar amounts of environmental impacts if both use a collective heat pump and are insulated according to nearly-zero energy building standards. The comparison between the environmental impacts of extensive renovations and building replacement depends on the expected building life span after the intervention, the quantity of solar panels, and the use of sustainable materials. Renovations including lower energy efficiency levels or fossil energy sources cause more environmental impacts. The MPG+ method aligns with the Dutch policy context but lacks transparency, completeness, and data certainty. The alternative scenarios in this study are compared per square meter, so the overall environmental impacts may increase if the relative apartment size per resident is greater in the new building. Considering the Climate Agreement, the housing crisis, and many uncertainties, extensive renovations are recommended as a no-regret solution for housing corporations.

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.

The EU has set out to reduce negative impacts from electricity generation on the environment, human health and towards our dependence on fossil fuels. As the fastest growing renewable source of electricity, photovoltaics plays an important role in the energy transition. The manufacturing of photovoltaic modules requires materials classified as critical, making them prone to supply disruptions. Although these materials are essential to the EU economy, they are not sufficiently recovered at the end of a photovoltaic module’s life. An alternative intermediate solution could be to extend the lifespan of existing modules, to slow down demand for these materials in the future.
The aim of this study was to analyse the theoretical options and practical examples of product life extension strategies for photovoltaics. The R-Ladder was used as a guiding framework, which provided examples of life extension strategies. These include Reuse, Repair, Refurbishment, Remanufacture and Repurpose. Aspects for each of these strategies were analysed to find potential benefits and challenges related to four aspects: economics, environment, energy, and materials.
The approach of this study includes a literature review to identify the life extension strategies discussed specifically for photovoltaics in the context of the circular economy. This was followed by a multi-case study on practical applications of Reuse, Repair and Repurposing of photovoltaic modules. Findings from literature and the case study were further supplemented with the insights from six experts. These experts had diverse backgrounds in research, manufacturing, and procurement to offer a variety of insights and perspectives on life extension strategies for photovoltaics. Finally, two scenarios were created for possible life extension pathways for used photovoltaic modules to illustrate the potential impacts compared to a commonplace premature replacement scenario.
Economics and module performance are key factors in decision-making and acquisition of a photovoltaic system. Reuse offers a compelling alternative to current recycling capabilities but offers no sufficient business case. Repair may extend a module’s lifespan to continue the generation of renewable electricity but is only possible in cases of minor damage for which replacement parts are available. Refurbishment could restore more severe damage but is limited by economies of scale and the technical difficulties resulting from current photovoltaic module design. Remanufacturing has the potential to restore a solar cell’s original performance or even upgrade it using newer processing methods but suffers from the same design limitations as Refurbishment. Repurposing used modules can offer a pathway to extract the remaining capacity if it is implemented in a context where generation density is of no concern. Combined, these strategies could buy time to address the resource challenges amplified by the energy transition.

This research focused on the role of cross-laminated timber (CLT) in the transition to a circular and bio-based housing sector in the province of Zuid-Holland (PZH). A scenario-model framework was used to assess the socio-economic and environmental impacts on the construction sector, as a result of CLT construction in general and as a result of different timber material origins. The central research question is: “What are the impacts of a transition to a housing sector in PZH that is for 20% based on CLT? and could regional CLT production offer socio-economically and environmentally sustainable solutions?”. The outcomes from the scenario analysis show that regional production of CLT is beneficial from a socio-economic perspective, while simultaneously being environmentally sustainable. The CLT required to reach the CLT implementation aim in PZH is sufficient to operate a price-competitive CLT industry. On paper, national timber flows are sufficient to produce this CLT and if national timber flows are not adequately available sawn timber should be imported from other European countries. The most important action points are related to increasing the domestic timber stock, ensuring high-grade application of timber, standardizing and bundling of demand for CLT construction, and ensuring adequate carbon policies to create a financially level playing field.