The increasing demand for sand in the construction sector underscores the need for sustainable alternatives to natural sand. This bachelor's thesis explores the application of Fine Recycled Concrete Aggregate (fRCA) produced by Heating air and classification system (HAS) from the Concrete To Cement and Aggregate (C2CA) technology as a sustainable substitute for natural sand. fRCA consists of pure sand and cementitious material, with the removal of extraneous substances such as timber and steel. While fRCA finds applications in various sectors, the challenges in its use in mortar include property variations, cost considerations, and the absence of quality control standards. Addressing these challenges would be crucial for the wider adoption of fRCA in mortar applications. This research aims to characterize fRCA properties, enhance fRCA quality through acid treatment and milling, determine optimal milling parameters, investigate the influence of the water-cement (W/C) ratio on mortar workability, and assess the compressive and tensile strength of mortar with fRCA. The central inquiry pertains to identifying the optimal approach for enhancing fRCA properties and integrating it into concrete mixes for civil engineering applications. The study is exploring the effects of untreated fRCA, milled fRCA, and acid-washed fRCA on mortar properties. It is also determined the ideal quantity of milled fRCA to replace natural sand in mortar mixtures. The theoretical evaluation of sustainability in mortar mixes utilizing this specific fRCA have been conducted. This research did not investigate the chemical properties of fRCA. Notably, the quality of fRCA differs from that of Natural Aggregate (NA), characterized by distinct particle size distributions and water absorption properties. While fRCA can effectively replace NA in mortar mixtures, it does affect compressive strength due to higher water absorption and the partial retention of cementitious material. However, by milling or treating it with ACID, the quality of fRCA can be improved, making it possible to use fRCA as a replacement for NS in mortars. The optimal substitution rate of NA with fRCA is identified as 25%, with the possibility of an increase to 100%, depending on the specific application. The integration of fRCA in concrete holds potential for sustainability by reducing reliance on natural resources and curbing waste generated by the construction industry.

Packaging plastics account for the majority of the household waste plastics. These plastics can be divided into a number of types of plastics, namely PET, HDPE, LDPE, PP, PS, EPS and others. However, many plastic packages consist of different types of plastics and are often contaminated, therefore these plastics end up in the mixed plastics. While monostreams of plastic waste still have a certain value the mixed plastics are worthless and accumulating. With an ever-increasing amount of mixed plastic waste, it is very important to recycle these plastics too. The EU, the Dutch government and municipalities in the Netherlands all have their sustainability goals. Almere as a municipality in the Netherlands wants to create their own mixed plastic household waste (MPHW) value chain to reduce their total amount of residual waste per citizen. The aim of this research is to find out how the municipality of Almere can encourage local recycling of MPHW. The research question of this research is therefore: What are opportunities to stimulate the niche of mixed plastic household waste recycling, in the municipality of Almere, and how can this be organized? To answer the research question there is made an overview of the plastic waste recycling infrastructure in the Netherlands and interviews are held with the municipality of Almere and with companies that are active in the recycling of MPHW. To be able to analyze the developments a theoretical framework has been designed which is based on the multi-level perspective, strategic niche management and business model innovation. The results show that municipalities in the Netherlands, such as Almere, have gained more control over their own waste processing. Almere can stimulate developments in the local niche for recycling MPHW by creating the right conditions such as a guaranteed supply of MPHW and demand for products made from these plastics. Technological innovations in the recycling of mixed plastics can be conducive to the success of the niche when Almere brings the various players together. Successful development of the local MPHW niche in Almere can stimulate other municipalities to follow their example.

Fine sieved fraction (FSF) is a solid waste generated from wastewater treatment plants (WWTPs). Cellulose fiber is the most important component of FSF, which can be fermented into volatile fatty acids (VFAs) and then be used as carbon sources in biological nutrient removal (BNR). This thesis measured and evaluated the aerobic & anaerobic biodegradability of solids in fermented FSF (fFSF) and the BNR performance of FSF-derived VFAs. In addition, this research tested the feasibility of using secondary sieving as a potential downstream processing technology. The products of secondary sieving (liquid: secondary filtrate, solid: secondary FSF) were compared with fFSF in terms of biodegradability and BNR performance. The aerobic biodegradability of raw FSF, fFSF and secondary filtratewere 52.3 ± 1.4, 60.4 ± 4.7 and 72.1 ± 6.4 %, respectively. The anaerobic biodegradability of raw FSF, fFSF and secondary FSF are 56.8 ± 8.4, 68.2 ± 6.4, 51.5 ± 7.8 %, respectively. The results of biodegradability revealed that secondary sieving increased the proportion of readily biodegradable solids and reduced the overall organic load of activated sludge systems. The residual solids after secondary sieving could be converted into biogas or recovered as building materials. FSF-derived VFAs could substantially increase denitrification rates and phosphate release rates. fFSF and secondary filtrate could increase the denitrification rate by 40 - 50%and increase the phosphate release rate by around 200 % compared to blank. Theoretically, the effluent nitrogen load could be reduced by up to 53.7%if FSF-derived carbon sources are fully used for denitrification atWWTP Aarle-Rixtel. If used for phosphorus removal, the capacity provided by FSF-derived VFAs could nearly remove all phosphate from the effluent. To sum up, FSF-derived VFAs could effectively increase BNR rates and significantly reduce the effluent nitrogen and phosphorus load. The main advantages of FSFderived VFAs over conventional carbon sources are sustainability and waste-reduction. Secondary sieving could reduce the solid load of activated sludge tank and achieve a combined recycling of VFAs and fibers, but the total COD available for BNR will be reduced as a compensation. The results in this thesis can facilitate the application of fFSF in WWTPs and the improvement of FSF-derived VFAs production.

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.

The ambition of the Netherlands is to have a fully circular economy by 2050. One of the steps to achieve this ambition is that in 2030 the tenders should have circular ambitions at all governmental levels. However, at the moment, there are insufficient tools for the municipality to make the practical implications of these circular ambitions explicit. In a studied case-project in Reigersbos (Amsterdam), where circular facades are being applied, a selection procedure has taken place to unify different parties that are willing and able to enhance the circularity of the project. Such a tender process is complex and time-consuming. A tool that streamlines circular requirements can help the selection procedure for the parties involved early in the process and can actively keep track of realisation of the set requirements during the process. Therefore, the thesis aims to develop a circular tendering tool that actively helps the municipality and project developer set circular ambitions and criteria for an arbitrary project location. The tool’s concept is to categorize and assess the individual benefits of the circular measures in the chosen products, phases and parties, based on the principle of the circular economy. By utilizing this tool, it becomes possible to compare and select a facade system for the project. Furthermore, it also keeps track of the process by monitoring the set goals during the project for necessary adjustments and allows evaluating of the goals in the end.

Mining projects around the world face a significant challenge to reduce their footprint and be more environmentally friendly. Research has shown that mineral processing is of major influence, due to the use of heavy chemicals that are both expensive and polluting. Currently, electrowinning (the electrodeposition of metals) is only used in the last purification step of the process. So far, the majority of the studies on cobalt have focused on non-electrowinning possibilities. Therefore, it is of interest to investigate the electrochemical behaviour within different environments to obtain more information and gain a better understanding. This thesis focuses on the electrochemical behaviour and deposition of cobalt-bearing minerals, which will be evaluated with the help of cyclic voltammetry (CV) and the electrochemical quartz crystal microbalance (EQCM). These techniques use the help of multiple variable input parameters, which will be investigated and compared to gain the optimised condition to perform the experiments. Furthermore, the sensitivity of the techniques to different input parameters and different solutions will be investigated. This is done to investigate what the origins are for the differences in the electrochemical behaviour of copper-cobalt minerals in aqueous solutions using analytical, synthetic and real ores, and to find a correlation between the obtained results using the graphs generated using CV and EQCM-techniques. This is done to investigate to possibilities using selective electrowinning, meaning the electrodeposition of multiple elements within the same electrolyte solution. Based on a review of the literature, the experimental setup used for the experiments will be discussed to gain better understanding of the specialised equipment and corresponding software. Cobalt chloride, cobalt sulphate and copper sulfate solution will be evaluated first, after which two synthetic cobalt-bearing minerals containing iron will be tested. With the help of CV, the electrochemical behaviour, e.g. redox- reactions, can be analysed. Using the EQCM, accurate measurements of the mass change per unit area of the electroplated cobalt will be recorded. Synthetic minerals will be used to discover how much can be recovered using this technique. Finally, six samples from the Democratic Republic of Congo (DRC) will be evaluated to obtain the same data as for the synthetic minerals. For this QEMSCAN data is used to evaluate the mineral composition. Analysis of the results demonstrated that under different circumstances in different environments, similar electrochemical behaviour and the occurrence of copper, iron and/or cobalt deposition is observed. However, for special cases these reactions do not occur. This difference can be explained by a varying mineralogy, where bornite and chalcopyrite have a positive effect on the electrochemical activity. Regarding the shape of the voltammogram, the number of electrons involved in the reaction has the largest influence. Furthermore, alkaline conditions have a positive effect on the electrodeposition of cobalt. No overall correlation has been found between the samples. For all experiments similar reactions and electrochemical activity is observed regarding the peak potentials and within the same environment, correlations can be found. Recommendations for further research are to investigate the influence of changes to parameters such as temperature, magnetic field and impurities on the electrochemical behaviour of the reaction and changes in the yield of electrodeposited material, to generate more data to validate and calibrate the characteristic potentials that can be used for selective electrowinning and to gather more data of the selective electrowinning experiments in terms of additional (rare) elements, such as lithium.

In order to help the building and construction sector move towards a Circular Economy and lower its environmental impact, a better founded choice regarding the design and selection of building materials for a building’s load bearing structure is required. By investigating different design strategies that focus on optimizing various aspects of the Circular Economy, an office building can be designed in such a way that it matches both the initial client’s requirements as well as possibly changing future needs. Different design strategies then lead to varying lay-outs of a building’s load bearing structure and the building material it’s made of. By ranking ten design perspectives in varying orders, three main design strategies can be formed. The first one maximizes a building's technical service life, thereby limiting the use of new materials and energy during maintenance activities. The second strategy aims for a maximal functional service life, by making the original building fit for possible other functions in the future. The final strategy maximizes a building's residual value, which includes re-use of building elements in new projects. The next step is to link these design strategies to various criteria that can be included in the Multi Criteria Analysis. This results in a total of nine criteria, some of them being linked to the characteristics of a building material and the type of connections that come with that material. Other criteria depend on the design of a load bearing structure, such as the total weight of a structure, its ECI value and a cost indication. Now, all these MCA criteria can be given different weights, according to their level of importance per design strategy. Finally, the MCA as explained above, can be tested on a case study from Witteveen+Bos. Based on the Program of Requirements as formulated by the client, both design strategy 2 and 3 could be followed during the design phase. The main difference between these two strategies can clearly be seen in the lay-out of the load bearing structure’s. After completing the MCA for both strategies, it can be concluded that a bolted steel structure is most likely the best option for design strategy 2. On the other hand, a bolted CLT structure seems to be the best solution when designing according to design strategy 3 for this specific case study. Concluding these results, it can be stated that the MCA can indeed help in selecting a design and building material, however in some cases, the differences between some building materials seem limited. Therefore, it can be said that the MCA is more likely to be helpful in eliminating some of the building materials from next design steps, based on their low MCA results.

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

This experimental thesis explored the technical feasibility of a temperature-controlled dissolution-precipitation process for recycling polyolefin household wastes. An extensive literature review defines the experiment's feed composition and experimental setup. Additionally, it inspects the potential for the process to become a sustainable addition to the existing plastic recycling system along with a basic analysis of the major costs of a commercial plant. The study involved 5 experiments with the characterization of its outputs. The results demonstrate that the technique can handle common organic contaminates and non-target polymers in the feed without compromising the quality of the polymer product. The polymer products present characteristics that are comparable to the feed, which mostly consist of food-grade packaging. Suggesting the potential application of polymer products in the food and beverage industry, closing the loop for plastic use.

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.

Large quantities of mine tailings are stored in mine tailings storage facilities. These facilities are only costing money for mining companies. In addition, these tailings storage facilities are prone to failure. To prevent this from happening these facilities have to be reinforced. This research introduces a concept to use geotextile tubes filled with mine tailings as reinforcing construction elements. That way value is assigned to the mine tailings while also making the storage facilities safer. However, pumping mine tailings in geotextile tubes is not an option due to the small particle sizes which will flow through the openings in the geotextile fabric. In addition, the contaminations in the mine tailings will also be mobilised using this method. Therefore, this research investigates potential enhancement of mine tailings to make them suitable to be pumped in geotextile tubes. The potential enhancement is in the form of flocculation and remediation. While flocculation increases the dewatering properties of mine tailings, the remediation will prevent the contaminations from mobilising. Test performed in this research include a series of jar tests, cone tests, two different strength tests and hanging bag tests. The results show that when flocculants are added to the tailings, the dewatering rate increases. The flocculant type which proved the most effective for these specific tailings type is a flocculant with an average molecular weight and average anionic value. Adding coagulant to the tailings further increases the dewatering rate of the tailings. When Ordinary Portland Cement is added, to stabilise and solidify the tailings, the dewatering rate increases even more. In addition, adding Ordinary Portland Cement to the tailings resulted in an increase of shear strength and unconfined compressive strength. After seven days of curing, the highest strength of curing was measured for the mixtures where fifteen mass percentage Ordinary Portland Cement was added. The mixture where the highest strength and the fastest dewatering rate was measured, was the mixture composes of mine tailings, flocculants, coagulants and fifteen mass percentage Ordinary Portland Cement. With these results, it may be concluded that mine tailings can be used to fill geotextile tubes to form reinforcing construction elements if its dewatering behaviour is enhanced and its contaminants remediated.

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.

Construction and demolition waste form a significant problem in terms of environmental pollution and material depletion. Concrete, as part of construction and demolition waste, is already responsible for 9% of the total anthropogenic carbon dioxide emissions. Consequently, it is important to alleviate the environmental stress of concrete by replacing virgin aggregates and cement by recycled aggregates and liberated cement. This study determines how the properties of recycled aggregates and virgin (new) aggregates compare for using recycled aggregates in a new concrete mixture. Recycled aggregate properties are examined by performing a variety of experiments, namely water absorption and specific gravity, Los Angeles abrasion, flakiness and shape index and compressive strength. Each experiment describes a different characteristic of the aggregates creating a clear picture of their properties. The properties of virgin aggregates have been obtained from literature. In addition, a milling method has been examined as a possible new step in the recycling chain for liberating cement paste from the fine recycled aggregates. Water absorption and interfacial transition zone formed problems for the recycled aggregates, but they show excellent properties in terms of compressive strength, resistance to abrasion, grain interlocking and shape characteristics. While very different from each other, recycled aggregates show very good properties when compared to virgin aggregates giving them potential to be used in new concrete mixtures.

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.

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.

Waste management in Lagos State is an unrelenting issue as the population increases exponentially per annum; there is a constant struggle with organization, transportation, and disposal of the daily waste generated per capita within the city. Of the waste generated in households in Lagos, plastic makes up a large percent of the non-organic waste found in dwellings. Waste from residences often end up pooling by the street side, and recycling is slow in gaining traction within the city. In addition, tropical cities like Lagos use HVAC systems to deal with high temperatures; this gives rise to high energy consumption in dwellings and offices alike. This is noteworthy because high energy consumption usually translates to energy expenses and in this city, with a population of 22 million, about 8.5% live in poverty with the middle-income earners toeing the line. Although a passive strategy like the use of thermal mass in buildings could improve energy efficiency, it is deemed more effective in regions with a significant difference in diurnal temperatures (>10°C). In Lagos state, however, there is no such significant range in temperatures. This served as the motivation for the inclusion of another strategy to support what is already existing – thermal insulation. This study explored the impact of thermal insulation made from plastic waste on energy savings and energy costs with the aid of DesignBuilder used to model dwellings with the climatic conditions of Lagos state. The focus of this study was on middle-class citizens in Lagos State and a survey was conducted using an online tool called Survicate, to assess their perception of the use of plastic waste on their facade. From the data, it was deduced that there is a possibility that people are willing to use plastic waste as thermal insulation when they are aware of the reduction of energy costs. For this study, five variations of thermal insulation were constructed, and experiments were carried out with the use of a hotbox to determine the thermal conductivity of these samples. The first sample was made from PET bottles with its cavity filled with textile waste; the second sample, a mould created from melted PET plastic that had been cut into tiny bits; the third variant was constructed from PET bottles with its cavity filled with water sachets (LDPE); the fourth sample, was built from crushed PET bottles and water sachets; and the last sample was made from empty PET bottles stacked on top of one another. The test sample with the least capability produced an expense reduction of N774.36/m2.year (€1.94/m2.year), while the best performing had a cost reduction of N1100.57/m2.year (€2.75/m2.year). Regardless of which insulation sample is applied, there would be savings in energy consumption, the cooling load demand of RAC (residential air-conditioning) systems would also decline, and there would be monetary savings as well. Resulting from the study’s outcome, it was recommended that a physical model be built in Lagos State to be studied further to see how well the materials perform under the actual climatic conditions in Lagos.

Zinc smelters in the European Union are now facing a lot of problems, especially under the attack of the Covid-19. This study reviewed the situation of the zinc smelting industry in the EU, including production methods, application of raw materials, pollution control, and waste treatment. The vast majority of smelters use hydro-metallurgical process to obtain high-purity zinc products. Roasting – leaching – electro-winning method is well developed, accepting a large range of raw materials and also has economic advantages. However, the problem with this method is the generation of large amounts of leaching residues. Many researchers have been worked on this and proposed many solutions. It can be improved by increasing leaching efficiency and can better recover valuable metals from the leaching residues. As for environmental pollution in the zinc smelting industry, sulphur emissions have been under well control, and both waste water and solids can be partly recycled in the process. But the storage and disposal of leaching residues are the main problems that still exist and need to be resolved.