Recycling, Volume 4, Issue 3 (September 2019) – 14 articles

Some industrial wastes are shown to be useful in the production of mullite ceramics. These industrial wastes are rich in certain metal oxides such as silica (SiO₂) and alumina (Al₂O₃). This gives wastes the potential to be used as a starting material source for mullite ceramics preparation. The purpose of this review paper is to compile and review various mullite ceramics preparation methods that utilized a variety of industrial wastes as starting materials. This review also describes the sintering temperatures and chemical additives used in the preparation and its effects. A comparison of both mechanical strength and thermal expansion of the reported mullite ceramics prepared from various industrial wastes were also addressed in this work. Full article

This study seeks to find the influence of replacing a portion of the asphalt–rubber binder with the bio-based material “guayule resin.” This replacement could be beneficial in terms of sustainability, economics, and environmental concerns related to the asphalt industry. Nine asphalt–rubber–guayule binders were investigated to find their rheological properties. Consecutively, the study proceeded with five selected binders being compared to the original asphalt (PG64-22). Investigations underwent whole matrices (crumb rubber modifier (CRM) residue included) and liquid phases (CRM residue extracted). Additionally, these properties were partially sought for their corresponding asphalt–rubber binders to compare and judge the contribution of the guayule resin. Likewise, a thermo-gravimetric analysis was done for the guayule resin to recognize its moisture and composition complexity. Such an analysis was also done for the as-received CRM and some extracted CRMs to determine the release and residue of rubber components. Outcomes showed that the guayule resin has the potential to compensate the performance required against the original asphalt at elevated temperatures while greatly decreasing the asphalt cement proportion. For instance, a blend of 62.5% asphalt, 12.5% CRM, and 25% guayule resin provided better performance than that of the original asphalt. Full article

The melt conditioned direct chill (MC-DC) casting process has been used for the production of billets of AA-6111 alloy formulated from recycled aluminium derived from incinerator bottom ash (IBA). The billets were homogenised and then extruded into planks. Optical metallography of the MC-DC billets showed equiaxed refined grains in comparison to DC and grain refined (DC-GR) billets formulated from the same scrap source. Microstructure evaluation for the extruded planks showed a less extensive peripheral coarse grain (PCG) for the MC-DC sample. Full article

The recovery of valuable metals from waste printed circuit boards (WPCBs) is crucial in order to harness their economic resources, and prevents potential environmental contamination. However, selective extraction of Cu and Zn, and the co-extraction of other metals as impurities at ambient temperature using selected lixiviants such as HCl, H₂SO₄, HNO₃, trifluoromethanesulfonic acid (TFMS), NaOH, and mixtures of NaCl and CuCl₂ was studied. It is shown that the extraction efficiencies of all the metals increased with increases in lixiviant concentrations. High selectivity of Cu and Zn toward Fe were achieved in dilute H₂SO₄, HNO₃, TFMS, and 0.5 M NaCl + 0.1 M CuCl₂, and low dissolution of Pb (<5%) was observed in all H₂SO₄ lixiviants. Almost 100% Zn extraction using NaOH lixiviants without trace of other metals was achieved. Therefore, 0.5 M NaCl + 0.5 M CuCl₂, 1.0 M HNO₃, 0.5 M H₂SO₄, and 1.0 M TFMS showed high extraction selectivity toward Cu and Zn with low chemical consumption, and produced pregnant leach solution rich in Cu and Zn, as well as residue containing Fe, Ni, and other metals. Full article

This paper studies the utilization and management of the waste mollusk shell. The two major export countries of mollusk shell are the Southeast Asia’s Thailand and the Philippines. First, the aquaculture of oysters and bivalve shells has been studied as background understanding. The effect of the global climate change on farming and the consequences of farming on the nearby environment and neighborhoods have also been discussed. The utilization technologies on the waste shell are available on a small scale and not industrialized. This study offers an enabling context under which a suitable method can take action to solve the overflow waste shell problem, and at the same time, provide sustainable management. Full article

The treatment of end-of-life vehicles generates large amounts of automobile shredder residue (ASR), a potential source of recycled metals. Reliable measurement methods are required to determine the composition of ASR and evaluate the resource potential. We reported on research undertaken to investigate bias and variability in the process of measuring trace metals in ASR. Two primary samples of shredder light fraction (SLF) underwent extensive physical sample preparation and chemical analysis. The samples were spiked to control random variations and systematic effects during physical sample preparation. Chemical analysis was conducted using wavelength-dispersive X-ray fluorescence spectrometry (WD-XRF), a fully validated wet-chemical analysis, and a wet-chemical analysis representing an “in-house” lab procedure. Physical sample preparation introduced deviations up to a factor of 2, likely due to preferential losses and heterogeneity. Deviations for WD-XRF measurements of elements were in the range +100%/−50%. In-house chemical analysis produced results that were in good agreement with validated results for Al, Fe and Sn, but led to biased results or high variability for Cd, Dy, La, Nd, Pb, Pd, Pt and Sb. To improve the chemical analysis of trace metals in SLF, we recommended reducing particle size to less than 0.1 mm before chemical analysis and using a larger number of repeated digestions. Full article

Polypropylene and polystyrene are petroleum-based thermoplastics which are commonly used and disposed of in the environment after their service life, leading to environmental degradation. There is a need to recycle polypropylene and polystyrene, but the effect of recycling on thermo-mechanical properties is not well understood. This study aims to determine thermo-mechanical properties of the recycled polypropylene and recycled polystyrene and compare them with corresponding virgin polypropylene and newly produced polystyrene (general purpose polystyrene 1540 and high impact polystyrene 7240). The study was carried out by preparing bar-shaped samples of recycled polypropylene, recycled polystyrene, general purpose polystyrene 1540, and high impact polystyrene 7240 by compression molding using a hot press and thermally characterizing them to determine glass transition temperature and melting temperature using differential scanning calorimetry. The changes in Young’s modulus, tensile strength, hardness, and toughness due to recycling activities were determined at room temperature (24 °C), 40 °C, 60 °C, and 80 °C. The thermo-mechanical properties of recycled polystyrene (PS) were found to be comparable to those of high impact polystyrene (HIPS) 7240. The study revealed that the hardness and toughness for the recycled polymers were higher than those of corresponding virgin polymers. On the other hand, tensile strength and Young’s modulus for the recycled polymers were lower than those of the virgin polymers. Understanding the thermo-mechanical properties of the recycled polymers will contribute to more industrial applications hence increase the rate of recycling, resulting in a reduction in environmental pollution. Full article

Considering that the large quantity of waste electrical and electronic equipment plastics generated annually causes increasing environmental concerns for their recycling and also for preserving of raw material resources, decreasing of energy consumption, or saving the virgin materials used, the present challenge is considered to be the recovery of individual polymers from waste electrical and electronic equipment. This study aims to provide an update of the main identification methods of waste electrical and electronic equipment such as spectroscopic fingerprinting, thermal study, and sample techniques (like identification code and burning test), and the characteristic values in the case of the different analyses of the polymers commonly used in electrical and electronic equipment. Additionally, the quality of the identification is very important, as, depending on this, new materials with suitable properties can be obtained to be used in different industrial applications. The latest research in the field demonstrated that a complete characterization of individual WEEE (Waste Electric and Electronic Equipment) components is important to obtain information on the chemical and physical properties compared to the original polymers and their compounds. The future directions are heading towards reducing the costs by recycling single polymer plastic waste fractions that can replace virgin plastic at a ratio of almost 1:1. Full article

The increase in the generation of used automotive lubricating oils is an issue of growing concern, especially in developing countries. Most used oil contains degraded additives and its indiscriminate disposal causes environmental degradation and pollution. This study investigates the characteristics of the reclaimed oil obtained by solvent extraction technology. It further evaluates the suitability of the reclaimed oil for reuse, by comparing its properties with the Society of Automotive Engineers (SAE) quality standards for lube oils. Three samples of used engine oils were collected, recycled and analyzed. Results from this study and other similar studies indicated that the flashpoint is below the SAE specifications. Viscosity index and kinematic viscosity at 40 and 100 °C are found above the SAE specifications. The pour point of the reclaimed oil is found below the standard values while the specific gravity concurs with the SAE standards. Total acid and total base numbers of the reclaimed oil indicated a low acid concentration. The study suggests an improvement on the flash point and the viscosity of the reclaimed oils for better lubricating performance in the automotive engines. Full article

The scope of this work covers a proposal for the implementation of sustainable, low-cost, environmentally friendly, and affordable housing for low-income people. This paper aims to address the current housing issues, namely that many people lack decent housing and that the built houses are usually of a poorly sustainable nature. The work consists of three main parts: an evaluation of housing sustainability, measurement of parameters related to their internal comfort and a simulation of thermal enclosure with the COMSOL Multiphysics^® software. An important objective is to propose a sustainability assessment format, which, besides being explained in detail, is presented in a percentage scale for ease of understanding. This work seeks a methodology for evaluating the level or degree of sustainability for the construction and inhabitation stages of housing. Using a prototype constructed with polyethylene terephthalate (PET) bottles, temperature and humidity were measured. There was a contrasting behavior of these two parameters, which tended towards an inverse behavior, except on cloudy or rainy days. The roof of the prototype contained some waste materials that provided thermal insulation: galvanized steel, polyethylene bags for upcycling as waterproofing, PET bottles, soil and endemic plants (green roof). The results obtained in the simulation are in accordance with the real internal behavior of the prototype. Full article

The use of recycled aggregate in new concrete has often been limited due to concerns over their quality and structural performance. This research aims to investigate the physical properties of recycled roof tile aggregate and its suitability for concrete production. Physical properties of recycled roof tile aggregate are compared to normal crushed stone aggregate. Effects of recycled roof tile aggregates on strength and durability of recycled roof tile concrete was compared with normal aggregate concrete using mechanical properties and durability tests. The experimental results showed that high water absorption and low strength of aggregate have a great effect on the workability and strength of the concrete containing recycled roof tile aggregate. Aggregate density, water absorption, crushing value and abrasion value of the recycled roof tile aggregate were found to be lower than crushed stone aggregate and concrete containing recycled roof tile aggregate had low strength and slow strength development. Similar durability performance of recycled roof tile aggregate concrete and normal aggregate concrete was observed except when exposed to freezing and thawing. Full article

The rates of waste generation in India have been increasing with increasing population and urbanization. Since higher education campuses are like mini autonomous cities, they can act as a model for solid waste management (SWM) and enhance sustainable development. SWM is the controlled generation, storage, collection, transport, processing, and disposal of solid waste considering public health, conservation, economics, and environmental conditions. A SWM program on campus will benefit the campus through reduced resource consumption and waste diversion. Developing countries like India are lacking behind in SWM from the developed countries which are using advanced technologies along with efficient management. This paper will analyze the issues related to SWM at IITR (Indian Institute of Technology Roorkee) campus and provide feasible solutions to be implemented at IITR campus for becoming zero waste campus. The SWM at the IITR campus is disorganized and incompetent. Lack of awareness and improper collection, imprecise segregation, exposed transportation, inefficient processing and disorganized disposal of solid waste are the major reasons for it. IITR has the potential to manage its waste properly through various techniques discussed in this paper. These would reduce the amount of waste diverted to landfills and the problems arising on campus due to solid waste, thus leading to a zero waste campus. Other campuses like IITR with similar context and issues can learn from this case study and work towards a zero-waste campus. This paper identifies a need to implement a robust SWM at the IITR campus in India. Full article

The circular economy (CE) concept is gaining traction as a sustainable strategy for reducing waste and enhancing resource efficiency. This concept has been adopted in some countries such as Denmark, Netherlands, Scotland, Sweden, Japan, China, and Germany while it is being considered by others including England, Austria, and Finland. The CE has been employed in the manufacturing, agricultural, textile, and steel industries but its implementation varies. It is against this backdrop that this study seeks to identify CE implementation in three pioneering countries (China, Japan, and Germany). A critical review and analysis of the literature was conducted. The results revealed enabling and core policies/laws for the development of the CE concept. It also identified the implementation structure of the CE in China, Germany, and Japan. In conclusion, the findings of this study are expected to serve as a guide for developing and implementing the CE concept in various sectors of the economy. Full article

The article compares the energetic qualities of fuels from waste with hard coal. A cogeneration system has been modeled based on the organic Rankine cycle (ORC) powered by the investigated fuels in order to identify possibilities as well as problems in use of fuels from waste in an exemplary cogeneration unit in distributed generation. The emission of thermal transition of the investigated fuels has been calculated on the basis of their energetic use in order to determine the aggregate impact on the environment, people’s health and the ecosystem. In order to conduct the research, Ebsilon Professional and SIMAPro software were used. The article demonstrated the energetic and ecological validity of the use of fuels form waste in small-scale combined heat and power (CHP). The energetic potential and influence on the environment, people’s health and the ecosystem depends on the quality of fuel, but the strict regulations for generating fuels from waste and the flexibility in forming them, allow for a product which is more beneficial economically and ecologically than hard coal. Full article