This thesis consist of the graduation project executed in cooperation with the municipality of the Hague, at design studio DIDID in the Hague. The beaches of the Hague are cleaned by so called beach cleaners. Beach cleaners are large tractor pulled screening machines that effectively screen/rake garbage from the beach. There is however a problem with these machines. Together with the garbage, large quantities of shells are taken in. This is in-desirable for three reasons. 1: Shells are materials that belong to a natural beach and should therefor not be taken away. 2: Shells help prevent beach erosion because of their sand-clinching characteristics. More shells mean less beach erosion. 3: Shells form a large weight fraction of the material collected by the beach cleaners and therefor account for a large part of the disposal costs. Leaving them on the beach will significantly decrease these costs. This thesis shows the development of the ShellSaver. The ShellSaver is an add on to the current Beach cleaners, It is situated within the large collection container on top of the beach cleaner and separates the shells from the collected garbage in three separation steps. A disc screen separates large garbage from small garbage and shells. The first zigzag wind sifter separates glass and iron from shells and plastics. In the second zigzag wind sifter the shells are separated from the plastics and are returned to the beach. A prototype of the concept was developed and tested on a sample taken from one of the beach cleaners. The chosen combination of separation techniques proved to be capable of executing the desired separation.

Policy makers have set the goal to reach a completelycircular economy by the year 2050 in the Netherlands. This means that theconstruction industry should shift from its current ‘take-make-waste’ approachtowards a circular approach. The number of buildings of more than 100 m inheight are increasing in the Netherlands, due to the lack of horizontal space.This means that strategies should be investigated on how high-rise buildingscan be constructed in a circular manner. It is found that there are currently alarge number of high-rise buildings that are being demolished. The main reasonfor these demolition cases is that building owners want to replace theirbuilding with a new one, with new technologies and perhaps a new buildingfunction. Abuilding that is adaptable to these changes would not have to bedemolished,  which is why the circularitystrategy of Design for Adaptability is interesting for high-rise buildings.There is a lack of research on the measurement of theDesign for Adaptabilitystrategy on the building level. Therefore, in this research a BuildingAdaptability Indicator is created to measure the adaptability of a building. TheBuilding Adaptability Indicator is constructed from a study on how adaptabilitycan be achieved in a building. It is found that building adaptability isgoverned by three sub-indicators: openness, reserved capacity, andfloor-to-floor height. The Building Adaptability Indicator helps structuraldesigners to prove what amount of adaptability can be achieved with a certainextra material use. It is found that the adaptability can be increased with126% by increasing the structural element dimensions by up to 60%, leading to atotal material volume increase of 38%. Additionally, it is found that purelyfrom amicro economics point of view, the investment into a high adaptabilitycannot be justified due to the high initial investment combined with a low rentincome. However, from a macroeconomics point of view, policy makers caninfluence the construction industry to invest in buildings with a lowenvironmental impact, which is already done by the Dutch government throughsubsidies. Currently, adaptability is not considered in the calculation of theenvironmental impact, which means that investors do not have an incentive toimplement adaptability in their buildings. In this research, the BuildingAdaptability Indicator I simplemented in the calculation of the environmentalimpact, which leads to the conclusion that buildings with a high adaptabilityare more interesting from a circularity point of view. It is concluded that atthe moment, only investors with circularity ambitions will invest in adaptablebuildings. Investors that lack circularity ambitions can be encouraged toinvest in adaptable buildings as well. This can be done by implementingadaptability in the calculation of the environmental impact, for which ownersof adaptable buildings will receive subsidies. This will shift the constructionindustry more towards adaptable buildings, which will prevent demolition andlead to a lower environmental impact across the industry.   

Recycled aggregate concrete is emphasized more and more nowadays due to its importance towards the construction industry and general welfare of our planet. Being such a significant feature with regard to universal sustainable development, every aspect of its properties should be evaluated, examined and optimized so that there is a well-known, well-described and ready to use product. This project aimed at correlating some of the established parameters of conventional concrete such as water absorption of the coarse aggregate fraction and the resulting compressing strength, only applied in the field of recycled aggregate concrete. Along with these two properties, a prediction model was sought for which would be able to forecast the mechanical strength of concrete based on its coarse aggregate composition. A series of experiments were performed on samples fabricated for water absorption tests and compressive strength assessment. In total, 112 water absorption samples and over 250 concrete specimens were prepared and examined for the respective attribute. These samples used natural aggregate as the base of the coarse aggregate portion of the mix design, alongside a series of so-called contaminants which replaced the gravel in certain concentrations. These contaminants included bricks, ceramic tiles, glass, wood, gypsum, plastics, mineral fibers and recycled sand concrete and were entirely based upon the C&DW composition globally. Further investigation was done on the inclusion of air within concrete so that contaminated concrete results could be equated to this constant. All water absorption tests were performed according to the current standards and concrete specimens were crushed after 7 and 28 days of curing in order to obtain their strength in compression, while the predictive model was initiated via the Minitab statistical software. The results indicated some interesting and promising trends. From both sets of experiments, it was evident that the water absorption of the coarse aggregate fraction was not the main contributor towards the strength development of recycled concrete. It had a minor influence, especially compared to the type of contaminant present and how much volume it took. Furthermore, samples with identical water absorption fabricated concretes with different strengths. Overall, plastics and wood had the most negative effect in terms of compressive strength, while bricks, tiles and glass seemed to affect this aspect in neutral or even slightly positive manner. EPS foam in very limited amounts yielded a notable 30 to 35% strength drop, while on the other hand, brick replacing 20% of the NA improved the strength by approximately 7% after 7 days and 2% after 28 days. In the end, based on all experimental input, a predictive model was developed, optimized and validated in several steps so that it was able to predict the water absorption of coarse aggregate, compressive strength after 7 and 28 days and equivalent air content based on the composition of the coarse aggregates. The back-end of the model is provided within the report as a MATLAB code.

Starting from the 1950s, plastic has found its way into many aspects of life; from packaging to transportation and construction. The annual global plastic production was estimated to be 330 million metric tons in 2017 and will be doubled within 20 years if the current growth rate persists. In Europe, packaging accounts for 40% of the annual plastic production. To decrease dependence on fossil fuels and the related emissions and reduce the negative impact of plastics that enter the environment, the EU targets to recycle 55% of plastic packaging material by 2025. A steady production of large quantities of high-grade plastic recyclate is essential to sell the recycled material on the market and substitute virgin plastics. But, achieving this high grade is difficult due to the wide range of polymers, including additives and fillers. This research focuses on the sorting step of post-consumer packaging waste in a Material Recovery Facility (MRF) that takes place before recycling. In MRF's, Near Infrared (NIR) sensor-based sorting systems are state of the art to create high-grade sorting products. NIR's use reflection spectra to identify and distinguish a range of materials including different types of polymers. However, while sorting, False Calls (FC) occur when particles are incorrectly classified leading to a loss of valuable material or contamination of the product. Thus, this research aims to increase the understanding of false calls of NIR sensor systems, contributing to higher quality sorting products. To reach this goal, possible causes of FC's and their dependencies on the feedrate, feed composition and feeding mechanism were identified. These causes were arranged into a framework consisting of six types of FC's. A distinction was made between errors that are working range related and those that are not. Particles outside the working range may be classified incorrectly even when fed in a monolayer and under perfect circumstances due to the properties of the particle. The created framework was applied to a NIR in an MRF in the Netherlands which was tasked to separate non-plastic particles and PVC from plastic particles. Experiments were performed to single out the probability of each type of error to occur for 13 material classes. Next, the test results were implemented in a statistical model and a Monte Carlo simulation was performed. In this research, the varying input values were used to imitate the changing feed composition. Three scenarios of adjusted feed characteristics were analysed using the statistical model. It was concluded that to optimize the sorting performance of the analysed NIR, all types of False Calls should be tackled. The feed of the analysed NIR contained a large share of particles outside the working range. So, even if the particles were to be fed in a monolayer the average grade of the product is expected to be around 85%. The combination of the experiments and the statistical model allows for an effective evaluation of the sorting performance and a clear indication of the most problematic aspects of the feed characteristics.

In 2017, the Dutch government has set the goal to achieve a 100% circular economy by 2050. A transition from the current linear economy towards a circular economy is necessary to reach this goal. In the circular economy, products at end-of-life are no longer seen as waste but will be reused as a secondary product or resource. The general aim of this research is to investigate the implementation of the circular economy concept in the public space. From this study, it became clear that Dutch municipalities are willing to implement circularity for assets released from the public space. However, the municipalities are not aware of the actions which are required to increase the circularity within its maintenance activities. A method is proposed which gives decision makers of a municipality guidelines to justify their decision for a maintenance plan of an urban area. This method includes PAVE (maintenance plan analysis tool to value enhancement of circularity in the public space): a tool which quantifies the environmental and economic impact of maintenance plans. To express the impacts four criteria were selected: the carbon footprint, financial footprint, material loss and monetary value loss. The tool follows a life cycle assessment (LCA) framework. In this research, the use of PAVE was investigated during the maintenance of a neighbourhood in Almere. It was concluded that to be able to implement PAVE in an effective manner, the asset database of the municipality needs to be updated to fill in the information gap. Part of the case area database was renewed to conduct an inventory of the assets in the selected urban area for this research. In PAVE, the impacts of the selected assets were calculated for both the circular project plan of the contractor and the traditional linear plan. PAVE indicated that using the new project plan for the case area results in approximately 1455 ton less CO2 emissions and is €4304000 cheaper compared to the traditional linear maintenance plan. Furthermore, PAVE demonstrated that the use of the new plan leads to 238 m3 and €424.000 less material and monetary value loss, respectively. In this research, it was evident that to select a maintenance plan among others, the tool should be included in the decision-making scheme of municipalities. By implementing PAVE, decision makers will be able to compare the impacts of different maintenance plans and select the most suitable plan based on environmental and economic considerations. The implementation of the tool can be ensured by making the provided budget dependent on implementation. Finally, the proposed plans of contractors should be evaluated on their circularity. Guidelines have been formulated to support the selection of the maintenance plan for urban areas in the public space.

The quality control of materials from waste is an important step for acceptance in new high-quality products. Given the large volumes and complexity of waste streams, this requires advanced sensor technology such as the Laser Induced Breakdown Spectroscopy (LIBS) investigated in this thesis. Recyclers often rely solely on manual sorting and visual inspection, which is far less reliable and accurate than sensor technology that enables automated inspection. The main source of waste in this thesis is demolition concrete. It is characterized by large amounts of moisty granular material, varying amounts and types of impurities, and a dusty environment. This presents a major challenge to introduce an optical inspection technique such as LIBS. The research starts with a literature study into the state of the art of LIBS as a material identification technique. This is followed by a more physically oriented literature review of the transient processes and parameters involved in ablation and plasma formation by a high power pulsed Nd:YAG 1064 nm laser. From this follows the development of models to account for the different processes and phases of the matter. To this end, the different transient processes are separated and analysed by making use of local equilibrium conditions. Subsequently, the influence of the optics and associated hardware that is necessary to obtain good optical data is investigated. This knowledge is supplemented by a study of light collection and data processing techniques to further improve the quality and reproducibility of the optical data, given the challenging conditions in a recycling factory. Subsequently, to better understand the potential and limitations of experimental LIBS data, the useful information about the chemical composition and technical properties of the material sample is tested under different conditions. The aforementioned separate physical models have been compiled into a complete plasma model (MLIBS for short). This can explain the properties and emissions of a laser induced plasma. This model can also be used in reverse to determine the composition of sampled elements in a laser induced plasma. The focus is on the ability not to average data to eliminate noise, but to use the data from each laser shot usefully for identification. This is called single-shot data and it is the most efficient way to implement LIBS in practice, because the price of LIBS hardware increases rapidly with the number of shots a laser has to deliver per second. The last part of research is on statistical techniques that can use all relevant information in LIBS data to make the best decision when it comes to identifying different complex materials. By accumulating statistics, the material composition of contaminated concrete waste flows can be determined more reliably. Based on the entire research in this thesis, a prototype LIBS platform has been developed and integrated with a conveyor belt for the inspection of demolition concrete in a recycling plant. The platform withstood harsh outdoor conditions and successfully demonstrated the capabilities of automated inspection with LIBS. Development of the prototype included the design and integration of a laser system, optics, electronic control equipment, real-time data acquisition system, spectral data processing software, and a weatherproof protective frame.@en

Effective recycling of municipal solid waste incinerator bottom ashes (MSWI-BA) and construction and demolition wastes (CDW) has proven to be a challenge, despite the high potential for recovering valuable metals in MSWI-BA and reducing the carbon footprint of the construction industry. The fundamental problem is caused by the combined presence of fines (-1 mm) and moisture. This combination forms agglomerates and fouls screens and other separation equipment, making it notoriously difficult to recover value from these waste-streams. @en

Phosphate is removed from wastewater to prevent eutrophication. Chemical phosphorus removal by iron dosing is commonly used for this purpose, where phosphorus is among others bound in the mineral vivianite (Fe(II)3[PO4]2 · 8 H2O). A molar Fe:P ratio of 2.5 in sludge will capture 70-90% of total phosphorus in vivianite after anaerobic digestion, a digestion method which offers ideal conditions for vivianite formation. Vivianite is paramagnetic, enabling it to be recovered by magnetic separation for recycling purposes. Phosphorus recycling from wastewater is of great importance, as in worst-case scenarios, 40-60% of all phosphate rock resources will be extracted by 2100. It is furthermore estimated that in Europe 20-30% of the fertilizer demand can be met by using phosphorus that ends up in sludge in European sewage treatment plants. To reduce processing costs of magnetic vivianite recovery, a pre-concentration step based on density concentration can be introduced, as vivianite particles are denser than organic material in sludge. This research investigated the feasibility of vivianite concentration from digested sewage sludge with a Multotec MX7 spiral concentrator. Spirals are applied in the mining industry for coal washing and pre-concentration of ores which are suspended in water. Particle separation on spirals is based on centrifugal and gravitational forces. Digested sewage sludge is more viscous than water, which affects the separation process on spiral concentrators. To investigate the influence of this high sludge viscosity on the spiral separation efficiency, laboratory experiments were performed. Diluting the sludge furthermore improved the concentration of solids towards the product flow. However, spiral efficiencies were only 9%, while efficiencies over 80% were found for synthetic sludge, meaning that particle separation was limited. The iron concentration was highest in the product outlet and increased with dilution. The phosphorus content, however, was similar for all outlets and dilutions, suggesting that only Fe minerals other than vivianite, such as siderite and pyrite, concentrated towards the product flow. Additionally, a concentrated bed of sand grains was observed near the column after a dilution of 20%. While diluting the sludge improved the concentration of sand and heavy Fe minerals, it did not induce vivianite concentration.

Aluminium is a vital component of the world's economy, thanks to its versatile applications. However, the environmental impacts of primary production result in a growing desire and societal pressure to develop more efficient recycling techniques. Secondary aluminium is produced at 5% of the energy consumption used to produce primary aluminium. Unfortunately, many recycling techniques suffer from an undesired loss in quality and material due to the complex particle shapes, variety of alloys, and contaminants. This research focuses on a state-of-the-art scrap sorting technique that aims to overcome the problems associated with the singulation of particles with sizes up to 500mm (max. diameter). Singulation is the process where a random particle flow is regularized into an individually spaced 1D file of particles. Subsequent particle identification and sorting into multiple categories increases scrap quality to allow for more efficient up-cycling. A combination of literature study, model simulations and setup experiments is used to study the effects of particle- and equipment properties on obstructing processes. Firstly, this study focuses on three particle properties: Length-to-Width (LW) ratio, density, and complexity of shape. Four different samples are studied: Base case, high LW, high density, high complexity of shape. Obtained results show the adverse effects of increased LW-ratio on the singulation performance. An average LW-ratio increase from 2 to 6 decreases the singulation performance by 10-15%. Surprisingly, the expected frequent entanglement of complexly shaped particles was seldom observed. In addition, the flow of complexly shaped particles showed similar singulation rates compared to low LW particles. High density particles were only linked to minor obstructing events. Secondly, this study focuses on obstructing processes by studying the particle flow over and between setup equipment. Two processes are the most important: 1) transition behaviour (single particle flow) and 2) merging mechanisms (multiple particle flow). Video analysis has shown the adverse effects of unpredictable particle flow upon transitioning between setup stages. This results in an entirely random process, thereby deteriorating performance and rapidly wearing the chute surface. Unpredictable flow on the chute is primarily related to specific yet frequent circumstances. The amount of correction in flow a particle requires to align into a single file seems the best indicator. Centre-fed, parallel orientated particles require the least correction. Edge-fed, perpendicularly orientated particles require most. The latter is associated with the highest degree of unpredictable rolling. This observed phenomenon increases with particle size. The chute is designed to merge particles with crossing trajectories. Merging particles rotate around their point of contact as a whole until the combined bounding box is orientated parallel to the direction of flow. This explains the poor performance of high LW particles and surprisingly good performance of complex-shaped particles. The bounding box of merging high LW particles is already orientated parallel to the direction of flow. Limited rotational force is therefore exerted on the particles. In addition, the higher moment of inertia and chute design further restrict rotation towards sequential flow. Consequently, the current singulation process functions below its potential. The passive singulation process benefits from a reject of high LW particles towards the coarse faction (to be re-shredded) and smooth transition designs to reduce unpredictable flow.

Aluminium recycling is a crucial process when it comes to recycling of metals. To make the metal industry part of a circular economy, this process must be efficient and for the interest of companies it should be economical. Singulation is such a process which does both the tasks. In this work, aluminium scrap recycling has been positioned as a commercially beneficially process which encourages companies to take up the process and since the process is environmentally advantageous as well, there has been mentions of how the authorities provide policies which support this process. The first part of the work looks at how and why aluminium is produced which looks into the processes such as Bayer and Hall-Heroult and into multiple uses of the aluminium alloys and also mildly touches upon some of the compatible alloy series. Aluminium is a highly recyclable material so it is interesting to study about what happens one it has reached its End of Life (EOL) stage. Sorting is an essential stage in the recycling of aluminium and there are solutions which encourage sorting based on alloy series which again is economically and ecologically beneficial. And for this to happen efficiently, singulation is essential. Singulation of aluminium is important to achieve better efficiency in the process of recycling which is the aim of companies such as Reukema. Although useful, singulation has many challenges. Since it is a solution which depends on the problem i.e., there is no universal way to singulate every kind of material, the problem here has challenges such as entangling of material, their landing on top of each other are just some of such problems which are looked at here. By simulation, it was found that the arrival pattern of the material follows a homogenously random distribution for smaller size fraction but a highly regularized distribution for large size fractions but smoothens to a homogenously random distribution as we increase the number of particles for both size fractions. The experiments performed after developing a time series were compared to a simulated singulation process and the results were not ideal in terms of singulation since the chute was not included in the process. The experimental setup needed to be optimised which could lead to even better and accurate results. Higher particle speed on the vibrating feeder could have played a crucial role.

The energy transition makes us less dependent on fossil fuels, but it also brings a new dependence to the table: a dependence on critical metals for green technology. This study used an Exploratory System Dynamics Modelling and Analysis approach to analyse the transition to a circular lithium system towards 2050 and the potential effectiveness of the Battery Regulation. It was shown that the Battery Regulation is likely to increase the end-of-life lithium recovery rate. However, it is yet unsure whether the set of policies is robust in preventing recycling from coming at the cost of lifetime-extending strategies. Furthermore, even with a successful implementation of the Battery Regulation, the contribution of circularity strategies to increase supply and reduce demand is limited in the short term. It is therefore recommended to improve the prioritisation of lifetime extending strategies and to give extra focus to decreasing the material intensity of our economy.

Nowadays environmental issues like the depletion of the natural resources and the pollution of the environment have led many researchers to make new projects about the reuse of waste from construction and demolition again in concrete industry. Among available solutions are the partial replacement of cement with recycled ultrafine particles (RUP) and the reuse of recycled sand (RS) as substitute of natural sand in mortar/concrete mixtures. The aim of the present research is to investigate if the new mortar with recycled ultrafine particles can substitute the reference mortar made of virgin materials and to investigate the possible accompanying ecological and economic benefits. This will be demonstrated in terms of technical feasibility, ecology and economy of the new mortars. For the investigation of the main target of this MSc thesis, it was important three different experiments to be conducted. The 1st and 2nd experiment included the partial substitution of cement with RUP in 5%,10% and 15% respectively. The only difference was the size of RUP. In the 1st experiment were used only RUP below 125 microns and in the 2nd experiment only milled RUP below 45 microns. The 3rd experiment was more complicated with the simultaneous presence of RUP below 125 microns and the total replacement of natural sand with recycled sand. The w/b ratio was constant for the first two experiments at 0,5, but the w/c was increased as the replacement ratio of RUP also increased for all the experiments. The results were excellent about the fresh workability of the mortars in all the experiments with higher values of slump in contrast to the reference one from virgin materials. But there were some problems about the mechanical properties and especially the compressive strengths of the new mortars. The usage of smaller RUP below 45 microns improve the mechanical properties of the mortars with the highlight of the higher values for all the mortars in the test of flexural strength in the measurement after 14 days. Generally, it seems that as the replacement ratio of RUP was increased, the compressive strength of the mortars was decreased. For the 3rd experiment, the results regarding the mechanical properties were not very satisfactory despite the compensation with extra water. The quantity of this water has a crucial role for future researches and additionally lower replacement ratio than 100% is suggested for recycled sand.The next step was to reveal the possible ecological advantages from usage of this new mortar with recycled cement paste. For this investigation, an ecological analysis was conducted. This ecological analysis included in the first part a simulation in the lab experiments and in the second part a simulation in a conceptual recycling plant. The results are pleasant for the both cases regarding the GHG emissions and especially CO2. Initially, in the lab experiments, 5 % substitution with RUP instead of cement particles leads to 5,1% reduction of CO2 emissions, 10% substitution with RUP leads to 10,2% reduction of CO2 emissions and 15 % substitution with RUP leads to 14,8% reduction of CO2 emissions. Moreover, for the simulation of a conceptual recycling plant, the reuse of RUP in the mortar/concrete industry can lead to significant reduction of CO2 and less air pollution. Especially for the scenario in this MSc thesis, there is a potential environmental gain with total CO2 offset of 70,75 ton/day from this conceptual recycling plant. Up-to-day, the calcination of limestone to produce cement contributes to the emission of carbon dioxide. But the usage of recycled cement paste can reduce this bad consequence. The last step the investigation for the potential economic benefits from the reuse of the recycled materials and especially RUP in mortar/concrete industry. For this business case, an integration of Cost-Benefit Analysis with Cash-Flows was conducted for the previous conceptual recycling plant. According to this economic analysis, there are benefits from the creation of market for RUP, recycled sand and coarse aggregate like gravel and their demand as well as from the compensation by the European Union due to the reduction in CO2 emissions in this innovative conceptual recycling plant. The results revealed that the NPV was 5.955.631€ >0 for forecast of 18 year-operation. This can lead to a great payback period of the investment of about 33 months without the calculation of the taxation inside and with the conceptual discount rate at 10%. It has great perspectives for circular economy, with less waste, reuse of materials, less consumption of natural resources and less carbon emissions.In conclusion, although some technical drawbacks, the usage of RUP in new mortars instead of cement seems very satisfactory, and especially smaller RUP have beneficial effect to the mechanical properties of the mortar. Recycled sand is a material that needs more investigation about the appropriate parameters. The reuse of recycled materials and especially RUP contribute to some ecological advantages regarding the CO2 emissions. Also, there are possibilities for economic benefits for recycling plants with RUP as targeted material in products leading to the potential model of circular economy. Finally, RUP and other recycled materials can be the basis for sustainable and green development. Hence, recycled cement paste has as an impact the development of sustainable mortar in this industry.

With the acceleration of global urbanization, most of us will live in cities in the future. As the urban population grows, the shortage of residential buildings has become a more and more severe problem. In response to the rising demand for housing, more and more builders in Europe, East Asia, Australia and other places have begun to adopt a method called modular construction to build houses. By pre-constructing building components off-site, then combining them into a complete modular unit and transporting them to the building site for assembly, this approach can cut construction time in half and significantly reduce on-site labour costs (Hong, 2020). Modular construction is well suited for tall buildings due to its inherent topological modular form and increased number of repeatable modules (Thai, Ngo and Uy, 2020). However, most builders currently do not consider the concept of circularity when producing modules, let alone how they will be dismantled and reused in the future. It is conceivable that in the end a large number of discarded modular units will be sent to landfills, creating a large amount of solid waste and consuming many resources to dispose of them, while the functionality of the module still can work to fit the demand. Suppose we can consider the concept of circular economy at the beginning of the project and design the modular units to be easily disassembled and reused, in that case, we will benefit not only economically, but also significantly reduce the carbon footprint of the project. Based on the problem, it can be found that there is currently a research gap between circular economy and modular buildings. And there is still no tool for evaluating the circularity of modular buildings based on their characteristics. Therefore, this study aims to propose a method for circularity measurement based on the characteristics of modular buildings and modular construction. A review of design strategies for circular construction reveals a number of recognised strategies. Depending on the characteristics of modular construction, design for durability, adaptability, disassembling and reusability can be selected as suitable circular strategies for modular construction. From a structural point of view, an evaluation method called Module Circularity Indicator (MCI) was developed. The method takes into account the structure, the connection method and the loading capacity of modules and assigns a weight to each structural factor based on the results of a questionnaire in order to evaluate the circularity of the modular unit on a numerical basis. Project owners and designers, especially structural engineers, can use this method to evaluate the circularity of modular projects in terms of four dimensions. A study using student accommodation as a case was carried out to explore the economic and environmental impact of MCI. Through the case study, it was found that a higher MCI score does not lead to better economic returns and that investors need additional incentives to invest in more sustainable modular buildings. Furthermore, a higher MCI can reduce the environmental impact of a project to some extent, but the materials used in the modules are also important. In order to achieve a circular economy in the construction industry, MCI could be used as an indicator to subsidise highly circular modular buildings in order to encourage owners to invest in highly sustainable projects. This will allow the modular building industry to move towards more circular projects and reduce the environmental impact of the construction industry.