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Recycling, Volume 3, Issue 3 (September 2018)

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Cover Story (view full-size image) Plastic is an indispensable everyday material. From food packaging to sensitive medical [...] Read more.
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Open AccessArticle Compressive Strength and Leaching Behavior of Mortars with Biomass Ash
Received: 7 August 2018 / Revised: 6 September 2018 / Accepted: 17 September 2018 / Published: 18 September 2018
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Abstract
This study investigated the use of a biomass ash produced by a fuel combination made with wood, corn stover, and corn cob as cement replacement for the production of mortar. Biomasses are now widely accepted as a substitute for conventional fuels and are
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This study investigated the use of a biomass ash produced by a fuel combination made with wood, corn stover, and corn cob as cement replacement for the production of mortar. Biomasses are now widely accepted as a substitute for conventional fuels and are becoming essential for cost-effective production of energy. This study aimed to provide an opportunity for the annual agricultural corn-crop residue, corn stover and cob, which is increasingly being used as fuel for its valuable energy content. Measurements of workability, compressive strength, and leachate properties (pH, salinity, heavy metals and calcium ion release) of mortar specimen, at different cement substitution levels and ages, were evaluated. The results obtained reveal definitive possibilities for such mixed biomass ash to be used in cement-based materials, such as mortars. Moreover, a multiple regression analysis has been reported between the mass of calcium ions leached and the mixture composition with the compressive strength. Data show that further confirmation, on a longer span of time and of other types of mechanical properties and environmental tests, would be necessary to fully implement the use of such biomass ashes in various types of cement-based construction materials, in order to divert them from landfill disposal. Full article
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Open AccessArticle Sustainability Assessment of Waste Management System for Mexico City (Mexico)—Based on Analytic Hierarchy Process
Received: 28 July 2018 / Revised: 7 September 2018 / Accepted: 7 September 2018 / Published: 12 September 2018
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Abstract
Mexico City introduced the new legal waste norm Norma NADF-024-AMBT-2013 in July 2017. This report compares the proposed system with three alternatives: a baseline scenario with composting of organics, a scenario which involves anaerobic digestion of organics, and a mechanical–biological treatment scenario with
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Mexico City introduced the new legal waste norm Norma NADF-024-AMBT-2013 in July 2017. This report compares the proposed system with three alternatives: a baseline scenario with composting of organics, a scenario which involves anaerobic digestion of organics, and a mechanical–biological treatment scenario with no source separation. The comparison was done using an Analytic Hierarchy Process. Eleven different indicators were chosen for the evaluation: general waste performance indicators (landfill disposal and recycling rates), environmental indicators (greenhouse gas emissions, acid gas emissions, Biological Oxygen Demand (BOD), and mercury content in water and soil), economic indicators (investment and operation costs) ($ per Mg municipal solid waste (MSW)), and social indicators (jobs created and social acceptance). The scenario ranking based on pairwise comparison made by 5 experts from Mexico City showed that the most sustainable scenario, environmentally, socially, and economically, is that which corresponds to Norma NADF-024-AMBT-2013 with a ranking priority of 30.78%. Full article
(This article belongs to the Special Issue Waste Management Practices in Developing Countries)
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Open AccessArticle Recycling and Reuse Technology: Waste to Wealth Initiative in a Private Tertiary Institution, Nigeria
Received: 5 August 2018 / Revised: 24 August 2018 / Accepted: 7 September 2018 / Published: 8 September 2018
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Abstract
The practice of collecting, treating, and managing solid waste prior to disposal has become a necessity in developing and modern societies. However, over the years, most waste has become regarded as having second-rate value and could be recovered and reused for valuable goods.
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The practice of collecting, treating, and managing solid waste prior to disposal has become a necessity in developing and modern societies. However, over the years, most waste has become regarded as having second-rate value and could be recovered and reused for valuable goods. However, the construction costs for conventional Material Recovery Facility(s) (MRFs) have been a major barrier for its implementation, and these technologies also require considerable technical expertise, which is not often available in developing nations for the successful operation of the MRFs. Covenant University, a private mission institution undertaking a waste-to-wealth scheme, is focused on managing and processing used materials to create reusable products. Such materials included PET bottles, paper waste, food waste from cafeterias, plastic food packs, nylon, tin cans, and others. Specific areas from the university which were chosen for the survey included the residential areas for staff and students and the two cafeterias. The waste generated was characterized so as to quantify the amount of recyclable waste generated, and also to find out which was most-occurring. The survey involved the use of structured questionnaires, on-site observations, and measurements. The study revealed that the average amount of recyclable waste generated per day in the institution were 55.56% food waste, 13.46% PET bottles, 12.64% other plastic, 9.63% nylon, 4.68% tin cans, and 4.03% paper. The study establishes that adequate waste characterization is a requirement for effective integrated solid waste management, which would boost resource recovery, reuse, and recycling. Full article
(This article belongs to the Special Issue Waste Management Practices in Developing Countries)
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Open AccessArticle Applying the Theory of Planned Behavior to Recycling Behavior in South Africa
Received: 30 July 2018 / Revised: 30 August 2018 / Accepted: 5 September 2018 / Published: 8 September 2018
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Abstract
This paper reports on an application of the Theory of Planned Behavior to understand the relationships between the determinants (latent variables) comprising the Theory of Planned Behavior and, based on these findings, to guide decision-making related to household recycling in South Africa. Data
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This paper reports on an application of the Theory of Planned Behavior to understand the relationships between the determinants (latent variables) comprising the Theory of Planned Behavior and, based on these findings, to guide decision-making related to household recycling in South Africa. Data from a representative sample of respondents in large urban areas (n = 2004) was analyzed using Structural Equation Modeling (SEM). The results of the SEM analysis showed a good fit of the survey data to the Theory of Planned Behavior theoretical model. The Theory of Planned Behavior explains 26.4% of the variance in recycling behavior and 46.4% of the variance in intention to recycle. Only 3.3% of South Africans in large urban areas show dedicated recycling behavior, considering the recycling of five materials: paper, plastic, glass, metal, and compostable organic waste. The recycling frequency item in the recycling behavior construct is the most likely to be over-reported. South Africans lack sufficient knowledge, positive attitudes, social pressure, and perceived control that would encourage recycling behavior. Awareness drives containing moral values (injunctive norms) and information about available recycling schemes, combined with the provision of a curbside collection service for recyclables, have the greatest chance to positively influence recycling behavior amongst South Africa’s city dwellers. Full article
(This article belongs to the Special Issue Waste Management Practices in Developing Countries)
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Open AccessArticle Water Electrolysis Anode Based on 430 Stainless Steel Coated with Cobalt Recycled from Li-Ion Batteries
Received: 4 August 2018 / Revised: 25 August 2018 / Accepted: 4 September 2018 / Published: 6 September 2018
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Abstract
In this paper, a new environmentally-friendly anode for hydrogen production was developed based on 430 stainless steel with an electrodeposited cobalt layer. The novelty of this work is the cobalt source once the electrodeposition bath was obtained from acid dissolution of a spent
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In this paper, a new environmentally-friendly anode for hydrogen production was developed based on 430 stainless steel with an electrodeposited cobalt layer. The novelty of this work is the cobalt source once the electrodeposition bath was obtained from acid dissolution of a spent Li-ion battery cathode. The oxygen evolution reaction on electrodeposited cobalt in 1 M KOH is compatible with the E. Kobussen mechanism. The water discharge is related with reaction determinant step in low overpotential. The cobalt electrodeposition (3 Ccm−2) promotes a significant improvement of 430 stainless steel anodic properties for oxygen evolution reaction. When the overpotential reaches 370 mV, the density current for 430 stainless steel with electrodeposit cobalt is 19 mA·cm−2 against 0.80 mA·cm−2 for 430 stainless steel without cobalt. Thus, the anode construction described in this paper is an excellent option for Li-ion battery recycling. Full article
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Open AccessArticle Barriers to Household Waste Recycling: Empirical Evidence from South Africa
Received: 30 July 2018 / Revised: 24 August 2018 / Accepted: 3 September 2018 / Published: 6 September 2018
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Abstract
A small percentage of South Africans regularly recycle most of their recyclables, which was only 4% and 7.2% in 2010 and 2015, respectively. This empirical quantitative study, the first study on this scale in South Africa, aimed to ascertain the reasons why people
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A small percentage of South Africans regularly recycle most of their recyclables, which was only 4% and 7.2% in 2010 and 2015, respectively. This empirical quantitative study, the first study on this scale in South Africa, aimed to ascertain the reasons why people do not recycle. This paper reports the results from a survey conducted among a representative sample of 2004 respondents in eleven of South Africa’s large urban areas. Each respondent selected three main reasons why people do not recycle from ten possible options as well as the one main reason. The results show that (i) insufficient space, (ii) no time, (iii) dirty and untidiness associated with recycling, (iv) lack of recycling knowledge, and (v) inconvenient recycling facilities are perceived as the main reasons why people do not recycle. Non-recycling households (74% of the respondents) give high priority to time and knowledge. Low recyclers—those that sporadically recycle few items—and young South Africans give high priority to services (inconvenient facilities and no curbside collection). Lack of knowledge is an important factor for people from dense settlements as well as the unemployed looking for work. Improved recycling services such as regular curbside collections have the potential to overcome time and space barriers. Recycling services as well as recycling knowledge will have to improve to encourage the youth, the unemployed, and those living in informal areas to recycle and realize the opportunities locked in the waste sector. The perceptions of respondents from non-recycling households differ from those from recycling households. The larger representation of non-recyclers in developing countries emphasize the importance of understanding local evidence when comparing and implementing results from developed countries. The learning from this study could also assist other developing countries to encourage household participation in recycling initiatives. Full article
(This article belongs to the Special Issue Waste Management Practices in Developing Countries)
Open AccessArticle Public Policy for Solid Waste and the Organization of Waste Pickers: Potentials and Limitations to Promote Social Inclusion in Brazil
Received: 25 July 2018 / Revised: 19 August 2018 / Accepted: 30 August 2018 / Published: 4 September 2018
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Abstract
The management model for the National Solid Waste Policy to develop sustainable actions, proposes the social inclusion of recyclable waste pickers in the waste management system. Compliance with the law, the form of participation of the waste pickers, and incentive mechanisms are configured
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The management model for the National Solid Waste Policy to develop sustainable actions, proposes the social inclusion of recyclable waste pickers in the waste management system. Compliance with the law, the form of participation of the waste pickers, and incentive mechanisms are configured as a relationship open to analysis. Therefore, the aim of this work was to investigate the potentials and limitations of a recycling cooperative, in terms of social technologies and inclusion, to encourage local development. The qualitative approach was aided by structured questionnaires, semi-structured interviews, and participant observation. The resulting evidence suggests that the organization of a cooperative, enabled access to information on the legislation of the National Solid Waste Policy. It showed the need to strengthen relationships with education institutions and public authorities. Despite the low levels of education of the members of the cooperative, projects and knowledge could be developed to aid social technologies. No technological innovations were observed, nor the production of alternative artifacts for recyclable materials. This weakens the cooperative in terms of articulation among peers, most notably the integration of the Catamare cooperative in the network of Cataparaná, to support the sale of material produced for industry. It may be concluded that joining the cooperative improved the social, economic, and political conditions of the members, but there were also structural limits to the recycling production chain that were not considered in the National Solid Waste Policy; and to a certain extent this weakens the development of sustainable actions. Furthermore, the organization of the cooperative hindered the development of social technologies and the social inclusion of the waste pickers. Full article
(This article belongs to the Special Issue Waste Management Practices in Developing Countries)
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Open AccessArticle The Feasibility of Using Marble Cutting Waste in a Sustainable Building Clay Industry
Received: 11 June 2018 / Revised: 27 August 2018 / Accepted: 29 August 2018 / Published: 3 September 2018
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Abstract
This study evaluates the feasibility of stabilizing clay bricks with marble cutting waste (MCW). This waste is currently discarded in huge quantities as sludge resulting from the sawing of marble blocks to slabs and the processes of disposing of grinding and polishing marble
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This study evaluates the feasibility of stabilizing clay bricks with marble cutting waste (MCW). This waste is currently discarded in huge quantities as sludge resulting from the sawing of marble blocks to slabs and the processes of disposing of grinding and polishing marble in landfills located around the marble processing factories in the Shaq El-Thoban industrial zone, Cairo governorate, Egypt, which causes negative impacts on the environment, health, and sustainable development. Experimental investigations were carried out to explore the effect of the addition of MCW in different clay–base mixes using varying percentages of up to 20% at the expense of the hydrated lime. Cement, hydrated lime, and MCW are the three types of solidification agents used, and clay and sand were also added in the formulations of the unfired clay brick specimens. Laboratory cylindrical stabilized and compressed specimens were made; then, they were cured in a humidity chamber for two weeks and four weeks. Afterwards, they were air dried, tested, and evaluated according to the Egyptian code for the building by the stabilized and compressed earth soil (ECBS, 2016). To enhance the durability of the cured specimens, transparent silicon-based paint was used. The results demonstrated that the optimum content of marble sludge waste (MCW) was 15% when used as replacement for hydrated lime in the production of stabilized clay brick. For all of the samples, the use of silicon-based paint was found to improve the strength and water resistance of the stabilized clay bricks. The use of local waste materials as a substitute for a hydrated lime binder reduces both the cost and environmental impact associated with block production. Full article
(This article belongs to the Special Issue Management and Disposal of Sewage Sludge)
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Open AccessArticle Predictors of Recycling Intentions among the Youth: A Developing Country Perspective
Received: 20 June 2018 / Revised: 10 July 2018 / Accepted: 9 August 2018 / Published: 16 August 2018
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Abstract
India is currently facing a mounting challenge related to municipal waste management, due to an increasing urban population, and their high consumption lifestyles. India also has the world’s highest number of young people in the 10–24 years age group. The study applied the
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India is currently facing a mounting challenge related to municipal waste management, due to an increasing urban population, and their high consumption lifestyles. India also has the world’s highest number of young people in the 10–24 years age group. The study applied the theory of planned behaviour (TPB) model to predict school students’ recycling intentions in Delhi, the capital of India and one of the highest producers of municipal solid wastes in the country. Data were collected from a school in New Delhi and the sample size consisted of 272 students from 9th and 10th grades. The TPB model explained 56% of the variance in the students’ intentions to recycling. The predictor ‘subjective norm’ appeared to have the strongest impact on the students’ recycling intentions, followed by ‘attitude’ and ‘perceived behavioural control’. It indicated that social factors are driving the Indian youth’s recycling intentions. It is important that the policymakers promote recycling as a social trend in India and provide adequate facilities to the public so that they can participate in recycling activities without facing difficulties. Schools also have a role in increasing students’ awareness of recycling and motivating them to participate in household waste management practices. Full article
(This article belongs to the Special Issue Waste Management Practices in Developing Countries)
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Open AccessArticle Performance Evaluation of the Physical and Combustion Properties of Briquettes Produced from Agro-Wastes and Wood Residues
Received: 5 July 2018 / Revised: 4 August 2018 / Accepted: 12 August 2018 / Published: 15 August 2018
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Abstract
This study investigated the physical and combustion properties of briquettes produced from agricultural wastes (groundnut shells and corn cobs), wood residues (Anogeissus leiocarpus), and mixture of the particles at 15%, 20%, and 25% starch levels (binder). A 6 × 3 factorial
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This study investigated the physical and combustion properties of briquettes produced from agricultural wastes (groundnut shells and corn cobs), wood residues (Anogeissus leiocarpus), and mixture of the particles at 15%, 20%, and 25% starch levels (binder). A 6 × 3 factorial experiments in a Completely Randomized Design (CRD) was adopted for the study. The briquettes produced were analyzed for density, volatile matter, ash content, fixed carbon, and specific heat of combustion. The result revealed that the density ranged from 0.44 g/cm3 to 0.53 g/cm3, while briquettes produced from groundnut shells had the highest (0.53 g/cm3) significant mean density. Mean volatile matter and ash content of the briquettes ranged from 24.35% to 34.95% and 3.37% to 4.91%. A. leiocarpus and corn cobs particles had the lowest and highest ash content, respectively. The briquette fixed carbon and specific heat of combustion ranged from 61.68% to 68.97% and 7362 kcal/kg to 8222 kcal/kg, respectively. Briquette produced from A. leiocarpus particles had the highest specific heat of combustion. In general, briquettes produced from A. leiocarpus particles and mixture of groundnut shell and A. leiocarpus particles at 25% starch level had better quality in terms of density and combustion properties and thus are suitable as an environmentally friendly alternative energy source. Full article
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Open AccessArticle Release of Trace Elements from Bottom Ash from Hazardous Waste Incinerators
Received: 11 July 2018 / Revised: 5 August 2018 / Accepted: 9 August 2018 / Published: 14 August 2018
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Abstract
Bottom ash is the major by-product of waste incineration and can contain trace elements (As, Cd, Co, Cu, Cr, Mo, Ni, Pb, and Zn) with concentrations up to thousands of mg·k−1. In this study, a combination of different extractions and leaching
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Bottom ash is the major by-product of waste incineration and can contain trace elements (As, Cd, Co, Cu, Cr, Mo, Ni, Pb, and Zn) with concentrations up to thousands of mg·k−1. In this study, a combination of different extractions and leaching tests (i.e., CH3COOH and ammonium-EDTA (Ethylenediaminetetraacetic acid) extractions and pHstat leaching tests) was used to investigate the potential release of trace elements from bottom ash samples derived from hazardous waste incineration plants. Although large variations have been found in the release of trace elements by different extractions, in general, the highest concentrations of most trace elements (except As and Mo) were released with the CH3COOH extraction, whereas the release of As and Mo was highest with the ammonium-EDTA extraction. Kinetics of element release upon acidification based on a pHstat leaching test at pH 4 could be related to the solid-phase speciation of some selected trace elements. The relatively high-potential mobility and elevated total concentrations of some trace elements imply a threat to the environment if these bottom ashes are not treated properly. Results of the present study may be useful to develop potential treatment strategies to remove contaminants and eventually recover metals from bottom ash. Full article
(This article belongs to the Special Issue Waste Management Practices in Developing Countries)
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Open AccessArticle Fast Electrochemical Method for Organic Dye Decolorization Using Recycled Li-Ion Batteries
Received: 2 August 2018 / Revised: 8 August 2018 / Accepted: 9 August 2018 / Published: 14 August 2018
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Abstract
In this paper, the application of recycled Li-ion battery spent cathodes (LIB-SC) combined with a NaHCO3/H2O2 system is presented for the first time in the literature as an alternative for the degradation of potentially toxic organic molecules. The
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In this paper, the application of recycled Li-ion battery spent cathodes (LIB-SC) combined with a NaHCO3/H2O2 system is presented for the first time in the literature as an alternative for the degradation of potentially toxic organic molecules. The model pollutant choice was methylene blue molecule. The spent cathode composition corresponds to LiCoO2, which was proved by the XRD and EDX. Regarding the decolorization of methylene blue solution, the addition of NaHCO3, in comparison with only H2O2, reduces the complete decolorization time by 96%. This reduction occurs because the radical CO 3 . is more stable than OH. In this way, the application of the system proposed in this article is aimed at solving two major global problems: the disposal of cell phone batteries and the pollution of liquid effluents. Full article
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Open AccessReview Microwave Technologies: An Emerging Tool for Inactivation of Biohazardous Material in Developing Countries
Received: 6 July 2018 / Revised: 27 July 2018 / Accepted: 1 August 2018 / Published: 2 August 2018
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Abstract
Inappropriate treatment and disposal of waste containing biohazardous materials occurs especially in developing countries and can lead to adverse effects on public and occupational health and safety, as well as on the environment. For the treatment of biohazardous waste, microwave irradiation is an
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Inappropriate treatment and disposal of waste containing biohazardous materials occurs especially in developing countries and can lead to adverse effects on public and occupational health and safety, as well as on the environment. For the treatment of biohazardous waste, microwave irradiation is an emerging tool. It is a misbelief that microwave devices cannot be used for inactivation of solid biohazardous waste; however, the inactivation process, and especially the moisture content, has to be strictly controlled, particularly if water is required to be added to the process. Appropriate control allows also inactivation of waste containing inhomogeneous compositions of material with low fluid/moisture content. Where appropriate, especially where control of transport of waste cannot be guaranteed, the waste should be inactivated directly at the place of generation, preferably with a closed waste collection system. In waste containing sufficient moisture, there are direct useful applications, for example the treatment of sewage sludge or human feces. A number of examples of microwave applications with impacts for developing countries are presented in this review. In respect to energy costs and environmental aspects, microwave devices have clear advantages in comparison to autoclaves. Full article
(This article belongs to the Special Issue Waste Management Practices in Developing Countries)
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Open AccessArticle Sustainability Impact Assessment of Increased Plastic Recycling and Future Pathways of Plastic Waste Management in Sweden
Received: 17 June 2018 / Revised: 11 July 2018 / Accepted: 20 July 2018 / Published: 22 July 2018
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Abstract
Plastic is a versatile material that has contributed to numerous product innovations and convenience in everyday life. However, plastic production is growing at an alarming rate, and so has the generation of plastic waste. Unsound waste management results in plastic leakage to the
[...] Read more.
Plastic is a versatile material that has contributed to numerous product innovations and convenience in everyday life. However, plastic production is growing at an alarming rate, and so has the generation of plastic waste. Unsound waste management results in plastic leakage to the environment with multiple adverse effects to ecosystems. Incineration of plastic waste produces excessive greenhouse gas (GHG) emissions, while plastic as a material is consumed and cannot be used again as a resource within a circular economy framework. For this reason, the European Union (EU) takes measures to increase plastic recycling, introducing higher targets for recycling in its revised waste legislation. Sweden follows suit, prioritising actions for improving the management of plastic waste. In this contribution, three scenarios of future plastic waste management are analysed for their sustainability impacts by 2030. The analysis is enabled by a plastic waste management flow model that calculates environmental, economic, and social impacts. The indicators used in the model to describe the impacts in each axis of sustainability are (1) GHG emissions, (2) monetary costs and benefits, and (3) number of jobs created. The results indicate several trade-offs between the different scenarios and between the different sustainability aspects of future plastic waste management, with their strengths and weaknesses duly discussed. Concluding, the most promising and sustainable future scenario for plastic waste management in Sweden includes high targets for recycling—in line with EU targets—and a gradual phase-out of plastic incineration as a waste management option. Full article
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Open AccessArticle Study of Temperature Fields and Heavy Metal Content in the Ash and Flue Gas Produced by the Combustion of Briquettes Coming from Paper and Cardboard Waste
Received: 16 May 2018 / Revised: 8 July 2018 / Accepted: 12 July 2018 / Published: 13 July 2018
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Abstract
The present study focused on the combustion of four types of briquettes made from paper and cardboard waste produced in Ouagadougou (Burkina Faso). Rotary and tubular kilns were used to study the combustion. The combustion mean temperatures, nitrogen, phosphorus and potassium (NPK) content
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The present study focused on the combustion of four types of briquettes made from paper and cardboard waste produced in Ouagadougou (Burkina Faso). Rotary and tubular kilns were used to study the combustion. The combustion mean temperatures, nitrogen, phosphorus and potassium (NPK) content in the ash and heavy metals content in the ash and the flue gas were analyzed. The combustion steady phase mean temperatures ranged from 950 °C to 750 °C were obtained according to briquettes type. The temperature favored the transfer of the heavy metal in the flue gas comparatively to the ash mainly for Hg, Cd and Pb. The Pb, Hg and Mn content in flue gas and the ash are higher than their content in the parent wood used for paper production due to the additive during the manufacturing process. The results showed a high content of heavy metal in flue gas produced by combustion of briquette made with office paper and in the ash for the briquette made of corrugated cardboard. Furthermore, the low heavy metal contain in the ash allow their use for soil amendment. However, ash contained a low proportion of NPK (less than 2%) which does not allow their usage as fertilizer alone. Full article
(This article belongs to the Special Issue Waste Management Practices in Developing Countries)
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Open AccessArticle A Proof-of-Concept Portable Water Purification Device Obtained from PET Bottles and a Magnetite-Carbon Nanocomposite
Received: 18 March 2018 / Revised: 22 June 2018 / Accepted: 28 June 2018 / Published: 1 July 2018
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Abstract
Widespread access to potable water is still far from being granted to populations of developing countries, especially in rural zones. For this reason, the development of easy-to-make, easy-to-use water purification devices is a topic of great social and economic importance. Poly(ethylene terephthalate) (PET)
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Widespread access to potable water is still far from being granted to populations of developing countries, especially in rural zones. For this reason, the development of easy-to-make, easy-to-use water purification devices is a topic of great social and economic importance. Poly(ethylene terephthalate) (PET) bottles are available worldwide, even in the remotest and poorest countries, as testified by the increasingly common practice of re-using bottles for solar water disinfection (SODIS). Here, we demonstrate how PET bottles could be re-used as a proof-of-concept water purification system. In this way, virtually the same bottle could be used first for SODIS and then for removing chemical contaminants. In the proposed approach, the bottles are treated with ethylenediamine to introduce amine groups, which are subsequently protonated with dilute acid. These functional groups allow the stable adsorption of a magnetite-activated carbon nanocomposite, which is prepared by a simple coprecipitation protocol. The efficiency of the nanocomposite and of the resulting prototype to remove model inorganic and organic pollutants (hexavalent chromium, industrial dyes) from water has been demonstrated. The proposed purification device is easy, cheap, and effective, all factors which could promote its use in developing and rural countries. Full article
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Open AccessArticle Modification of Refractory Concretes with Aeration Agents as a Method of Protection against the Phenomenon of Spalling
Received: 22 December 2017 / Revised: 3 April 2018 / Accepted: 19 June 2018 / Published: 24 June 2018
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The aim of the work is to carry out tests analyzing the effectiveness of introducing pores to concrete on eliminating explosive spalling of concrete in fire conditions. A fireproof concrete is designed, which contains aluminum cement and aggregate obtained from waste sanitary ware.
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The aim of the work is to carry out tests analyzing the effectiveness of introducing pores to concrete on eliminating explosive spalling of concrete in fire conditions. A fireproof concrete is designed, which contains aluminum cement and aggregate obtained from waste sanitary ware. A Microporan aerating agent is used to modify the concrete features. The tests are carried out on cubic samples with nominal dimensions 10 × 10 × 10 cm and cylindrical dimensions 10 × 20 cm. Three batches of test samples are prepared, with different levels of aeration of the concrete mixture, i.e., without an aeration agent, with 0.5% and a 1% amount of aeration admixture weighted relative to the amount of cement used. Samples of all batches are divided into two series and conditioned in two types of environments with different humidity levels: dry and humid. The article presents the results of strength tests of concrete samples that are subjected to high temperatures similar to the temperatures occurring in the fire environment. The process of heating the samples proceeds according to the standard curve showing the temperature rise during the standard fire. The soaking temperature is in the range of 20 to 1000 °C. After baking in the oven, the samples are tested on a strength machine. The authors carry out only pilot studies. Only results from destructive tests of compressive strength of a refractory concrete composite are presented. The simulation station for the fire impact is the PK-1100/5 high-temperature chamber furnace together with the control system and a computer station with temperature monitoring software. Samples are loaded with increasing temperatures, according to the “temperature–time” standard curve. The compressive strength test is used as a criterion for assessing the effectiveness of the aeration agent. Strength tests are carried out both on unheated and soaked conditions in different environments. This paper presents the results of laboratory tests that allow for the authors to determine the characteristics of the material being tested. The empirical data include, among others, testing of selected physical properties (water absorption of concrete) and mechanical properties (measurements of compressive strength before and after thermal load). Based on the results obtained, conclusions from the tests are formulated. The proposed considerations show that the modification of the composite by aeration is an effective preventive measure in relation to the phenomenon of explosive concrete spalling. Full article
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