Recycling, Volume 5, Issue 3 (September 2020) – 9 articles

Cocoa beans are found inside an outer husk; 60% of the cocoa fruit is the outer husk, which is a waste biomass. The husk cannot be used directly as a soil amendment as it promotes the fungal black pod disease, which reduces crop yield. The pods are segregated from the trees, and their plant nutrient value is wasted. This is particularly true for the small acreage farmers in West Africa. Cocoa pod husk is well suited to be used as a biomass source for electricity production. The waste ash is rich in potassium, which can be converted in various chemical products, most notably, high-purity potassium carbonate. This study reviews the information known about cocoa and cocoa pod husk, and considers the socio-economic implications of creating a local economy based on collecting the cocoa pod husk for electricity production, coupled with the processing of the waste ash into various products. The study demonstrates that the concept is feasible, and also identifies the local conditions required to create this sustainable economic process. Full article

Electronic components (EC) from waste electrical and electronic equipment (WEEE) such as resistors, capacitors, diodes and integrated circuits are a subassembly of printed circuit boards (PCB). They contain a variety of economically valuable elements e.g., tantalum, palladium, gold, and rare earth elements. However, until recently there has been no systematic dismantling and recycling of the EC to satisfy the demand for raw materials. A problem connected with the recycling of the EC is the removal of the components (dismantling) in order to recover the elements in later processing steps. The aim of the present study was to develop a new technique of dismantling using bioleaching technology to lower costs and environmental impact. In triplicate batch experiments, used PCBs were treated by bioleaching using an iron-oxidizing mixed culture largely dominated by Acidithiobacillus ferrooxidans strains supplemented with 20 mM ferrous iron sulfate at pH 1.8 and 30 °C for 20 days. Abiotic controls were treated by similar conditions in two different variations: 20 mM of Fe²⁺ and 15 mM of Fe³⁺. After 20 days, successful dismantling was obtained in both the bioleaching and the Fe³⁺ control batch. The control with Fe²⁺ did not show a significant effect. The bioleaching condition presented a lower rate of dismantling which can partially be explained by a constantly higher redox potential leading to a competition of solder leaching and copper leaching from the printed copper wires. The results showed that biodismantling—dismantling using bioleaching—is possible and can be a new unit operation of the recycling process to maximize the recovery of valuable metals from PCBs. Full article

Swedish recycling businesses argue that the Non-Toxic Environmental target gets too much weight and that resource efficiency gets too little focus, which results in decreased recycling. The purpose of this paper is to highlight different factors that recycling of waste decisions should consider, as well as contributing to a constructive discussion of the overall principles and policies for recycling. How recycling works in practice is explored based on nine interviews with stakeholders from the governmental agency level to recycling businesses. Theory with regards to ethics, risk, decision-making, governmental policy and laws is summarised. Finally, the discrepancy and connection between practice and theory is analysed. If recycling of waste is seen as a decision problem, the choice is between to recycle (in different ways) or not to recycle (i.e., energy recovery and/or landfill). Based on risk and decision theory, all relevant goals should be considered. This requires a broader problem framing when goals are in conflict. All parties agree that recycled and virgin material should be treated equally. From a higher policy perspective, it should then be demonstrated that any use of material (recycled and/or virgin) minimize environmental impact and promotes long-term sustainability. Full article

The electronic components mounted on the printed circuit boards (PCBs) of mobile phones represent a resource that is rich in metals, and after separation from the boards, these components could be considered secondary raw materials. The concentrations of the valuable metals are insignificant when compared with those of complete PCBs; however, they could be significantly higher in a fraction formed from the separated components. This study focused on the analysis of Ag, Au, Cu, Nd, Nb, Ni, Pb, Pd, Sn, and Ta in fractions produced by the separation of all the components mounted on PCBs from several types of mobile phones. Atomic absorption spectrometry, atomic emission spectrometry, and mass spectrometry techniques were utilized, and a comparison of five older models of “brick” phones and five modern smartphones was conducted. Additionally, 50 kg of PCBs from the current recycling market were analyzed in the same way to create a summary of the current recycling stream. Full article

Comprehensive knowledge of built-in batteries in waste electrical and electronic equipment (WEEE) is required for sound and save WEEE management. However, representative sampling is challenging due to the constantly changing composition of WEEE flows and battery systems. Necessary knowledge, such as methodologically uniform procedures and recommendations for the determination of minimum sample sizes (MSS) for representative results, is missing. The direct consequences are increased sampling efforts, lack of quality-assured data, gaps in the monitoring of battery losses in complementary flows, and impeded quality control of depollution during WEEE treatment. In this study, we provide detailed data sets on built-in batteries in WEEE and propose a non-parametric approach (NPA) to determine MSS. For the pilot dataset, more than 23 Mg WEEE (6500 devices) were sampled, examined for built-in batteries, and classified according to product-specific keys (UNUkeys and BATTkeys). The results show that 21% of the devices had battery compartments, distributed over almost all UNUkeys considered and that only about every third battery was removed prior to treatment. Moreover, the characterization of battery masses (BM) and battery mass shares (BMS) using descriptive statistical analysis showed that neither product- nor battery-specific characteristics are given and that the assumption of (log-)normally distributed data is not generally applicable. Consequently, parametric approaches (PA) to determine the MSS for representative sampling are prone to be biased. The presented NPA for MSS using data-driven simulation (bootstrapping) shows its applicability despite small sample sizes and inconclusive data distribution. If consistently applied, the method presented can be used to optimize future sampling and thus reduce sampling costs and efforts while increasing data quality. Full article

Management of waste streams from abattoirs is a major challenge in developing countries. Harnessing these wastes as resources for the production of biogas and biofertilizer could contribute to curbing the environmental menace and to addressing the problems of energy and food deficits in Nigeria. However, large scale uptake of the technology is faced with techno-socio-economic and the lack of data required for effective investment decisions. In this study, the potential use of waste generated in the north central region of Nigerian abattoirs, representing approximately 12% of the land and 6% of the population, were evaluated for suitability for biogas and biofertilizer production. Data acquired from the study sites were used for computational estimation and integrated into strengths, weaknesses, opportunities, and threats (SWOT) analysis to give a detailed overview of the prospects and the limiting factors. The study revealed that high investment costs and public subsidies for fossil fuels are the key limiting factors while the prospects of tapping into the unexploited carbon markets and multiple socio-economic and environmental benefits favors investment. Public supports in the form of national policy reforms leading to intervention programs are required for progress. Full article

The demand for more sustainable solutions has led an ever-growing number of stakeholders to being committed to pursue the principles of sustainability in pavement management. Different stakeholders have been looking for tools and methodologies to evaluate the environmental impacts of the solutions, for which the life cycle assessment (LCA) proved to be an appropriate methodology. This paper is focused on the LCA of road pavement multi-recycling based on the use of bituminous mixtures with high rates of reclaimed asphalt pavement (RAP). In order to promote the circular economy, a comparative analysis was performed on a road pavement section by taking into account different scenarios, which stem from the combination of production, construction and rehabilitation activities incorporating different RAP rates in new bituminous mixtures: 0% (as reference), 25%, 50%, 75% and 100%, respectively. LCA results have been expressed in terms of four damage categories: human health, ecosystem quality, climate change and resources. Results have shown that both recycled and multi-recycled bituminous mixtures lead to substantial benefits in comparison with the solution employing virgin materials, hence embodying a sustainable approach. The benefits grow with the increase in the RAP rate with an average decrease of 19%, 23%, 31% and 33% in all the impact categories for a 25%, 50%, 75% and 100% of RAP rate. Full article

In the present research, we investigated the conceivable outcomes of using ground tire rubber (GTR) particle polymeric blends. Special methods of restoring tires that are no longer in use include GTR retreading, GTR blending destined for recycling to attain raw substances utilized in other industrial application production processes, and the valorization of GTR for power/energy generation. The recycling of end-of-life tires enables the recovery of rubber, steel, and fibers, all of which are valid on the market as raw materials to be used for other processes. There are methods to recycle GTRs in a clean and environmentally friendly way. In the present research, several industrial applications of GTR polymer blends were developed and compared with standard values from the Spanish Association for Standardization (UNE) and the International Electrotechnical Commission (IEC). In order to analyze the viability in many of the industrial applications selected, certain compounds obtained from the GTR polymer blends were analyzed regarding their use in nine low requirement insulator applications. The research and analysis developed in this manuscript used standard values from the UNE and IEC, and these standard values were compared with the test values. The obtained results were used to provide an application list that could be helpful for industrial applications. In this research, the pre-owned polymers were as follows: polypropylene (PP), high-density polyethylene (HDPE), polystyrene (PS), acrylonitrile butadiene-styrene (ABS), ethylene vinyl acetate (EVA), polyvinyl chloride (PVC), and polyamide (PA). The filler used was GTR with particle sizes lower than 200 microns. The amounts of GTR particles in the compound materials were 0% (raw polymer), 5%, 10%, 20%, 40%, 50%, and 70% (the latter being found in polymeric blends). We discovered six plausible modern applications of GTR polymer blends as indicated by the UNE and IEC standards. Full article

Hazardous waste materials and their management are of prime importance to society. This article gives an overview of the current practices that relate to hazardous waste management. It looks at issues concerning the transboundary or international movement of harmful materials from industrialized nations to the developing and emerging world. This study has shown that Africa, most notably Nigeria, has become a dumping ground for hazardous waste materials as a result of the high importation of scrap computers and electronic devices into the country. The public health hazards, such as birth deficiencies, cancers, and even infectious diseases such as human immunodeficiency virus (HIV) and Hepatitis B and C, respectively, have been traced to the improper management of these waste materials. The review highlights a few models on hazardous waste management as developed by previous literature, which gives a hierarchy, ranging from source reduction, recycling, and landfill options. Studies reveal that hazardous waste management in Africa must revolve around wealth creation, economic, and environmental sustainability. The study provided evidence that the recycling option has high potentials in the areas of energy recovery. The data collected show South Africa to be the most advanced in the African continent in the field of hazardous waste management. For a sustainable environment, keen attention must be paid to hazardous waste management globally. Full article