Recycling, Volume 4, Issue 1 (March 2019) – 13 articles

The construction industry is faced with many challenges, among which is waste management. Aside from the fact that wastage contributes to time and cost overrun, it also has environmental implications in the form of pollution. However, the industry has the capacity to effectively manage waste, from generation to disposal. All stages of the management process are important, but scholars and governments have provided the final step, being disposal, unabated attention in order to ensure effective management. Potential waste disposal methods, including incineration, burning, landfilling, recycling, reuse, open dumping, pyrolysis, and shredding have emerged from the literature around the globe. Despite various waste minimisation and sustainable disposal options that are available, construction material waste is still increasing in Nigeria, while disposal remains a major issue for firms and government. Therefore, this study assesses disposal methods among construction firms to determine whether there is a relationship between their practices towards waste disposal. The research followed a concurrent triangulation design in a cross sectional survey, while data were collected via a convergent parallel mixed methods. The quantitative phase employed a structured questionnaire to collect data from 243 building construction firms, while the qualitative phase involved semi-structured interviews with 65 professionals from 10 on-going construction projects in Lagos, Nigeria. The research revealed that landfilling is the most common method of waste disposal, which is closely followed by reuse as backfill and recycling. In addition, the study revealed no association between company’s ownership statuses, age, project specialisation, and disposal methods, except company’s size. In conclusion, the study establishes the need for regulatory policies, such as site waste management plan (SWMP), pay as you throw (PAYT), and landfill ban, which would minimise material waste and divert them from landfills. Recycling and reuse are recommended as sustainable approaches for waste disposal. Full article

More than 250,000 metric tons (600 million pounds) of carpet are dumped in landfills every year. That creates a significant concern regarding environmental deterioration and economic liability. It is therefore imperative to develop sustainable post-consumer carpet-based products for high-value engineering applications such as composite tooling. To be considered as an acceptable composite tooling material, the composite needs to meet certain required properties such as a low coefficient of thermal expansion, excellent compressive properties, and high a hardness value after repeated exposure to curing cycles. The tooling composites must also exhibit the ability to endure several curing cycles, without deteriorating the mechanical properties. In the present investigation, post-consumer carpet has been recycled in the form of structural composites for tooling applications. The recycled carpet composites have been reinforced with 0.5 wt.% of graphene nanoplatelets to modify the material properties of the carpet composites. The results from compressive and hardness experiments demonstrate that the recycled carpet preserved its mechanical integrity even after several curing cycles. This indicates that recycled carpet composites have the potential to be a low-cost composite tooling alternative for the industry. Full article

Road deterioration inspires researchers to enhance the properties of asphalt binder for better performing mixes. Recycled tire rubber, or crumb rubber modifier (CRM), and used motor oil (UMO) are two modifiers that enhance asphalt binder performance through two different mechanisms. CRM affects high-temperature properties while UMO modifies low-temperature properties. Potential environmental concerns arising from the use of UMO have been raised in the literature. In this paper, the two recycled materials were investigated for their ability to complement each other. Both performance benefits of using both materials and the environmental concerns of using UMO were studied. Four CRM asphalt binders were investigated: two with UMO and two without UMO. Environmental impacts were evaluated using gas chromatography to check air emissions for benzene, toluene, ethyl-benzene, and xylenes (BTEX). The potential for toxic leaching of elements from modified hot mix asphalt (HMA) were checked using the US Environmental Protection Agency (EPA) Toxicity Characteristic Leaching Protocol (TCLP). For asphalt binders modified by CRM-UMO combinations, CRM decreased the amounts of released BTEX components, presumably by absorbing UMO and slowing the release of BTEX. Leaching results concluded that UMO mixtures showed a notable percentage of sulfur (S) as compared to non-UMO mixes. All these leachate components were under EPA limits. Full article

The recycling of waste plastics is considered as one of the strategies to tackle the issue of environmental pollution caused by commodity plastics all over the world. Recently, many universities have incorporated topics related to recycling and plastics waste management into their curricula at different levels to increase awareness as well as to develop new recycling technologies. In this study, one of the most important waste recycling problems is given as the project for the undergraduate students of chemical engineering to analyze the effectiveness of the project-based learning (PBL) approach in the school curriculum. A team of students was assigned with the task of recycling post-consumer polyethylene terephthalate (PET) bottles through an experimental and design approach. From the experimental data, students designed a recycling plant with a proposed capacity to produce 1 ton of recycled granules per day through the project-based learning approach. Evaluation of the project was carried out at various stages and it was found that the students acquired the required skills and applied them effectively. The outcomes of the present study clearly establish that the problems which have societal impacts, such as waste management, environmental pollution, etc., can be effectively communicated to the student community through the PBL approach, which can lead to increased motivation and enhanced critical thinking abilities. Full article

In this work, recycling of post-consumer carpets into structural composites using a modified vacuum assisted resin transfer molding process has been demonstrated. Fabrication of carpet composites addressed the problem related to the environmental effect of waste carpet. Application of the recycled carpet composite as the noise barrier structure has been studied in terms of noise absorption coefficient. Results show that the carpet composite absorbs noise better than conventional noise barrier at a wide spectrum of frequency. Effect of weather exposure on the carpet composite showed the degradation in the mechanical properties. Nanoclay films are also used on the carpet composite and show no change in the noise absorption ability. Full article

The main environmental issue associated with compost production is the production of a liquid leachate. Leachate from municipal wastes contains carbon, nitrogen, phosphorus, potassium and trace elements that can be used as nutrients by plants. The advantages of the use of organic wastes such as compost leachate as fertilizers are evident. Their use would reduce the consumption of commercial fertilizers, which need, with their production, high cost and energy. This work aims to determine the physical and chemical properties of a specific leachate with a variable composition, collected from the composting line of a mechanical and biological treatment facility. The goal is to assess if the leachates can be used as a potential source for fertilizers, and thus develop and design a sequence of processes which could effectively convert the leachates to commercial fertilizers according to the requirements of the proposal of regulation of the European Parliament of 2016 for fertilizers. Preliminary results show that the leachate samples qualitatively meet the requirements established for the composition of commercial fertilizers, especially organo-mineral fertilizers. Furthermore, there is no production cost of leachate as a raw material. The results show that the leachate is characterized by manageable concentrations of heavy metals which can be removed by adsorption processes, and it presents suitable amounts of organic carbon after a water removal procedure. However, the establishment of the conditions for suitable conversion processes are still under investigation considering the high composition variability due to factors like storage and environmental conditions. Full article

A successful circular economy can only exist when it relies solely on renewable energy sources. The adoption of resilient business models and the consequent redesign of legislation on all sectors are essential to ensure sustainable economic growth. Wind energy can offer clean and renewable energy with a low environmental impact. Nevertheless, waste in end of life composite materials resulting from wind turbines is a problem that needs to be addressed. Composite materials are commonly used in wind turbines due to their excellent mechanical properties, matched by low weight. Notably, the recycling technologies of such materials is limited. Material flows and estimations of end of life materials are of great importance and will convince stakeholders that markets for recycling composites are viable investments. Full article

Millions of tons of plastics are produced and consumed annually and should be recycled in a sustainable way. The effects of different compatibilizers on the properties of wood-mixed waste polymer composites are studied to promote recycling of plastics and to determine the potential of using waste plastics in composites. The effect of different addition levels and blending of compatibilizers is examined as well. The studied properties are microstructure, tensile and flexural properties, impact strength, and water absorption and thickness swelling in immersion. The results show that the addition of the selected compatibilizers improved the properties of wood-mixed waste polymer composites remarkably—all the studied mechanical properties and moisture resistance were improved by 50% or more. The effects depend strongly on the level of addition and the compatibilizer used. Findings show that compatibilization provides a feasible means to recycle waste plastics as feedstock for wood–plastic composites. Full article

The recycling of scrap is one of the common approaches aiming at reduction of mining-based production of critical metals and mitigation of their supply risk as well as processing-related environmental impact. The number of currently available end-of-life vehicles (ELVs) indicates—significant potential for critical metals recycling, especially niobium (Nb). Therefore, the quantification of environmental impact of niobium recovery starts to be an important issue in assessment of sustainability of large-scale recycling processes. In this paper, we assess energy consumption and greenhouse gas (GHG) emissions in individual stages of niobium supply chain in the automotive industry over the period 2010–2050. The different stages including mining, production and recycling are analyzed using dynamic simulation. The results show the majority of the consumed energy (45% of energy demand in niobium supply chain) is used in the primary production stage. This stage also contributes to 72% of total gas emissions of supply chain over the period 2010–2050. Mining of niobium consumes up to 36% of energy and generates ca. 21% of GHG emissions. While, in recycling stage, the secondary production of niobium requires 19% of supply chain energy and generates 7% of gas emissions. The detailed calculations show that recycling of niobium could save around 133–161 m GJ energy between 2010 and 2050. The recycling would also contribute to the reduction of 44–53 mt CO₂-eq in the same period. It shows around 18% reduction of annual emissions between 2010 and 2050 thanks to reuse of niobium in secondary production rather than primary production. Full article

Placing emphasis on promoting the reduction, reuse, recycling, recovery and repair of waste has been a critical aspect of the sustainable waste management agenda. Considering recycling, an environmentally friendly and sustainable waste management option, monetary rewards are in place for certain recyclable municipal waste materials in Finland. The study investigates consumers’ perception about the role of financial incentives in effecting the recycling of municipal solid waste materials in Finland. The study also considers drivers for recycling municipal solid waste on the basis of behavioural change factors, such as environmental risk, behavioural economics, resource value, economic benefit, convenience, knowledge, legislation and belief. It further determines the association between income-earning consumers and non-income-earning consumers in their perception of financial incentives for recycling. The empirical results from the study confirm that the role of financial incentive is important in accelerating the recycling of municipal solid waste. A weak-to-positive relationship exists between drivers for recycling municipal solid waste and recycling behaviour. There exists no statistically significant difference in the means of the perceived role of financial incentives for recycling in the two groups. The introduction of financial incentives for other recyclable wastes is required in order to boost consumers’ participation in the recycling of municipal solid waste. The need to pay more attention to intrinsic and extrinsic factors, as they affect the participation members of the society in the recycling of municipal solid waste, is paramount. This has become necessary in ensuring sustainable waste management in Finland. Full article

With changing consumption patterns, growing populations and increased urbanisation, developing countries face significant challenges with regards to waste management. Waste plastic is a particularly problematic one, with single-use plastic leaking into the environment, including the marine environment, at an unprecedented rate. Around the world, countries are taking action to minimise these impacts, including banning single-use plastics; changing petroleum-based plastics to alternative bio-benign products such as paper, glass or biodegradable plastics; and improving waste collection systems to ensure that all waste is appropriately collected and reprocessed or safely disposed. However, these “solutions” are often met with resistance, from business, government or civil society, due to the intended and unintended consequences, leaving many questioning the most appropriate solution to reducing the leakage. This paper argues that there is no one single solution to addressing the leakage of plastic into the environment, but that the solution is likely to be a combination of the three approaches, based on local considerations. Full article

This work contributes to waste management from two major perspectives. Firstly, waste generation in a previously not-studied location—Awka municipality—was sampled and characterized. Secondly, the characterization was done with improved accuracy using a new method called zero-intercept first-order polynomial regression. The proposed method arrives at composition values and per capita values through polynomial regression that considers sampled waste generation data and household size as regressors, respectively. There are no constituents when no waste is generated and there is no per capita waste when household size is zero, therefore, zero-intercept was imposed on the proposed linear regression approach. An 820 by 11 data matrix from a ten-day sampling in Awka Municipality was used to illustrate the proposed approach; eighty percent of the data was used for training, while twenty percent was used for testing. The results from the proposed method proved more accurate when compared with traditional averaging techniques. The results established for the study area are equally in consonance with known results for similar Nigerian locations, such as organic (73.2%), plastic (8.0%), and recyclable (20.3%). The calculated specific loose volume, specific compact volume, the loose bulk density, and compact bulk density are 2.0 × 10⁻³ m³/kg, 9.9 × 10⁻⁴ m³/kg, 500.0 kg∙m⁻³, and 1010.2 kg∙m⁻³, respectively. The waste generation rate is 416.9 g/capita/day, the organic waste generation rate is 307.1 g/capita/day, the recyclable waste generation rate is 83.0 g/capita/day, paper and textile waste generation rate is 25.2 g/capita/day, loose waste volume rate is 9.02 × 10⁻¹ dm³/capita/day, and compact waste volume rate is 4.51 × 10⁻¹ dm³/capita/day. The solid waste characters were compared among the three income groups of low, middle, and high income earners and the observed trends are literature compliant with city-specific coloration. City-wide estimations were made based on demography, literature, and the established results that would aid waste management planning. Full article