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. ... Read more

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. ... Read more

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.
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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. ... Read more

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. ... Read more

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. ... Read more

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.
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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. ... Read more

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. ... Read more