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Materials Recycling and Energy Use of Waste

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "B: Energy and Environment".

Deadline for manuscript submissions: closed (31 October 2021) | Viewed by 35107

Special Issue Editor

Spanish National Research Council (CSIC) – National Center for Metallurgical Researcher (CENIM), Madrid, Spain
Interests: materials recycling; metals removal; carbon nano adsorption technology; wastewater purification; hydrometallurgical operations
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Waste-to-energy (WtE) is the process of generating energy in the form of electricity and/or heat from the primary treatment of waste, or the processing of waste into a fuel source. WtE is a form of energy recovery. Most WtE processes generate electricity and/or heat directly through combustion or produce a combustible fuel commodity, such as methane, methanol, ethanol or synthetic fuels.

Waste thermal treatment processes with energy recovery are often suppressed in the circular economy scheme due to the belief that already minimized waste streams are not suitable for material recovery However, not all waste can be recycled, and in the future, other forms of waste management (such as energy recovery) have to be considered.

This Special Issue will focus on analyzing the technologies available for energy recovery of waste, including incineration, pyrolysis, gasification processes, and even the use of energy and materials in the cement industry. Different types of waste (municipal solid wastes, plastics, tires, and composites, among others) and the recovery of materials will be of interest in this Special Issue, paying attention also to the environmental problems derived from the processes described above, their effect on the climate, and its impact on the circular economy. In addition, it will be interesting to analyze the residual waste market and the future for WtE.

Prof. Dr. Felix A. Lopez
Guest Editor

Manuscript Submission Information

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Keywords

  • refuse-derived fuel
  • energy recovery
  • material recovery
  • greenhouse gas
  • circular economy

Published Papers (10 papers)

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Research

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13 pages, 1888 KiB  
Article
A Multidisciplinary Review of Recycling Methods for End-of-Life Wind Turbine Blades
by Ebbe Bagge Paulsen and Peter Enevoldsen
Energies 2021, 14(14), 4247; https://0-doi-org.brum.beds.ac.uk/10.3390/en14144247 - 14 Jul 2021
Cited by 34 | Viewed by 5494
Abstract
Wind energy has seen an increase of almost 500 GW of installed wind power over the past decade. Renewable energy technologies have, over the years, been striving to develop in relation to capacity and size and, simultaneously, though with less focus on, the [...] Read more.
Wind energy has seen an increase of almost 500 GW of installed wind power over the past decade. Renewable energy technologies have, over the years, been striving to develop in relation to capacity and size and, simultaneously, though with less focus on, the consequences and challenges that arise when the products achieve end-of-life (EoL). The lack of knowledge and possibilities for the recycling of fiber composites and, thus, the handling of EoL wind turbine blades (WTBs) has created great environmental frustrations. At present, the frustrations surrounding the handling are based on the fact that the most commonly used disposal method is via landfills. No recycling or energy/material recovery is achieved here, making it the least advantageous solution seen from the European Waste Commission’s perspective. The purpose of this research was thus to investigate the current recycling methods and to categorize them based on the waste materials. The opportunities were compared based on processing capacity, price, environment and technology readiness level (TRL), which concluded that recycling through co-processing in the cement industry is the only economical option at present that, at the same time, has the capabilities to handle large amounts of waste materials. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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19 pages, 2050 KiB  
Article
Exergy-Based Assessment of Polymers Production and Recycling: An Application to the Automotive Sector
by Sofia Russo, Alicia Valero, Antonio Valero and Marta Iglesias-Émbil
Energies 2021, 14(2), 363; https://0-doi-org.brum.beds.ac.uk/10.3390/en14020363 - 12 Jan 2021
Cited by 8 | Viewed by 2438
Abstract
In the last century, the economic growth has been accompanied by a worldwide diffusion of polymers for multiple applications. However, there is a growing attention to the environmental pollution and energy consumption linked to the unconditional use of plastic. In the present work, [...] Read more.
In the last century, the economic growth has been accompanied by a worldwide diffusion of polymers for multiple applications. However, there is a growing attention to the environmental pollution and energy consumption linked to the unconditional use of plastic. In the present work, exergy is used as a measure of the resource consumption during the life cycle of polymers. Nine commercially diffused polymers are chosen, and their production chains are identified according to the “grave to cradle” approach. The global Embodied Exergy (EE) is calculated as the sum of the contribution of each step of the chain, including the production process and the Exergy Replacement Cost (ERC) of the fossil fuel. Then, recycling routes and the associated exergy consumption are analysed. Thermodynamic recycling indexes are developed depending on the final product, namely the crude polymeric material and the oil derivatives or structural molecules. The main results show that some commonly used polymers have a considerable impact in terms of EE (e.g., PET). Recycling indexes encourage the recycling processes, which are always energetically convenient (from 10% to 60% of exergy savings) compared with the production from virgin raw material. Results from EE calculation are used for the thermodynamic assessment of the plastic content of vehicle components, to obtain useful information for recycling practices development. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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22 pages, 4229 KiB  
Article
Activated Carbon from Winemaking Waste: Thermoeconomic Analysis for Large-Scale Production
by Isaac Lorero, Arturo J. Vizcaíno, Francisco J. Alguacil and Félix A. López
Energies 2020, 13(23), 6462; https://0-doi-org.brum.beds.ac.uk/10.3390/en13236462 - 07 Dec 2020
Cited by 5 | Viewed by 2139
Abstract
An activated carbon manufacturing process from winemaking waste is analyzed. In that way, vine shoots conversion is studied as a basis for plant designing, and mass and energy balances of hydrothermal carbonization and physical activation are fulfilled. To develop an energy-integrated plant, a [...] Read more.
An activated carbon manufacturing process from winemaking waste is analyzed. In that way, vine shoots conversion is studied as a basis for plant designing, and mass and energy balances of hydrothermal carbonization and physical activation are fulfilled. To develop an energy-integrated plant, a network of heat exchangers is allocated to recover heat waste, and a cogeneration cycle is designed to provide electricity and remaining heat process demands. Furthermore, thermoeconomic analysis is applied to determine the thermodynamic efficiency and the economic viability of the plant. Energy balance indicates that heat exchangers energy integration covers 48.9% of the overall demands by crossing hot and cold streams and recovering heat from residual flue gas. On the other hand, the exergy costs analysis identifies combustion of pruning wood as the main source of exergy destruction, confirming the suitability of the integration to improve the thermodynamic performance. Attending to economic costs analysis, production scale and vineyard pruning wood price are identified as a critical parameter on process profitability. With a scale of 2.5 ton/h of pruning wood carbonization, a break-event point to compete with activated carbons from biomass origin is reached. Nevertheless, cost of pruning wood is identified as another important economic parameter, pointing out the suitability of wet methods such as hydrothermal carbonization (HTC) to treat them as received form the harvest and to contribute to cutting down its prices. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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15 pages, 3097 KiB  
Article
Assessment of the Synergy between Recycling and Thermal Treatments in Municipal Solid Waste Management in Europe
by Marco Abis, Martina Bruno, Kerstin Kuchta, Franz-Georg Simon, Raul Grönholm, Michel Hoppe and Silvia Fiore
Energies 2020, 13(23), 6412; https://0-doi-org.brum.beds.ac.uk/10.3390/en13236412 - 04 Dec 2020
Cited by 25 | Viewed by 3114
Abstract
In 2018, the production of Municipal Solid Waste (MSW) in EU-28 reached 250.6 Mt, with the adoption of different management strategies, involving recycling (48 wt %), incineration and thermal valorization (29 wt %) and landfilling (23 wt %). This work was based on [...] Read more.
In 2018, the production of Municipal Solid Waste (MSW) in EU-28 reached 250.6 Mt, with the adoption of different management strategies, involving recycling (48 wt %), incineration and thermal valorization (29 wt %) and landfilling (23 wt %). This work was based on the analysis of the baseline situation of MSW management in EU-28 in 2018, considering its progress in 2008–2018, and discussed the possible improvement perspectives based on a framework involving incineration and recycling as the only possible alternatives, specifically evaluating the capability of already-existing incineration plants to fulfill the EU needs in the proposed framework. The results of the assessment showed two main crucial issues that could play a pivotal role in the achievement of Circular Economy action plan targets: the need to increase the recycling quotas for specific MSW fractions through the separate collection, and therefore the improvement of definite treatment process chains; the optimization of the recovery of secondary raw materials from incineration bottom ash, involving the recycling of ferrous and nonferrous metals and the mineral fraction. Both issues need to find an extensive application across all member states to decrease the actual differences in the adoption of sustainable MSW management options. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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11 pages, 2533 KiB  
Article
Utilization of Boiler Slag from Pulverized-Coal-Combustion Power Plants in China for Manufacturing Acoustic Materials
by Jing Li, Xinguo Zhuang, Carlos Leiva, Celia Arenas, Ana Cornejo, Xavier Querol, Natalia Moreno, Oriol Font and Constantino Fernández Pereira
Energies 2020, 13(21), 5705; https://0-doi-org.brum.beds.ac.uk/10.3390/en13215705 - 31 Oct 2020
Cited by 2 | Viewed by 1785
Abstract
The potential utilization of boiler slag generated in large amounts from pulverized-coal-combustion (PCC) power plants has recently drawn much attention due to the serious problems caused to ecosystems. In order to make maximal use of the boiler slag and reduce the environmental risk [...] Read more.
The potential utilization of boiler slag generated in large amounts from pulverized-coal-combustion (PCC) power plants has recently drawn much attention due to the serious problems caused to ecosystems. In order to make maximal use of the boiler slag and reduce the environmental risk it poses, this study focused on manufacturing acoustic materials using boiler slag from Chinese PCC power plants. Three promising acoustic materials were successfully manufactured from up to 80% boiler slag with different grain sizes, with the addition of 20% Portland cement. The density and compressive strength of the products were inversely proportional and the sound absorption coefficient was positively proportional to the grain size of the boiler slag. The best sound absorption coefficient was obtained in products made from the coarsest fraction of the boiler slag (MS-C). Nonetheless, all the boiler-slag-based acoustic products still demonstrated compressive strength and densities comparable to those of other acoustic materials made of Spanish bottom ash or other conventional/recycled materials. The acoustic products made from the coarsest fraction (MS-C) and medium fraction (MS-M) of the boiler slag presented good noise absorption characteristics, like those of the commercial coarse porous cement that is traditionally used as an acoustic product. Furthermore, the acoustic products were characterized by very low leach ability of potentially hazardous elements. Consequently, the manufacture of acoustic materials is a very promising application for boiler slag. On the one hand, it consumes huge amounts of boiler slag that is generated in large amounts in China. On the other hand, the acoustic products can be used extensively to produce road acoustic barriers with a high sound absorption efficiency, no significant physical or mechanical limitations and no environmental implication. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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17 pages, 944 KiB  
Article
Thermochemical Treatment of Sewage Sludge Ash (SSA)—Potential and Perspective in Poland
by Marzena Smol, Christian Adam and Stefan Anton Kugler
Energies 2020, 13(20), 5461; https://0-doi-org.brum.beds.ac.uk/10.3390/en13205461 - 19 Oct 2020
Cited by 17 | Viewed by 2567
Abstract
Phosphorus (P) recovery from sewage sludge ash (SSA) is one of the most promising approaches of phosphate rock substitution in mineral fertilizers and might be a sustainable way to secure supply of this raw material in the future. In the current investigation, the [...] Read more.
Phosphorus (P) recovery from sewage sludge ash (SSA) is one of the most promising approaches of phosphate rock substitution in mineral fertilizers and might be a sustainable way to secure supply of this raw material in the future. In the current investigation, the process of thermochemical treatment of SSA was applied to SSA coming from selected mono-incineration plants of municipal sewage sludge in Poland (Cracow, Gdansk, Gdynia, Lodz, Kielce and Szczecin). The Polish SSA was thermochemically converted in the presence of sodium (Na) additives and a reducing agent (dried sewage sludge) to obtain secondary raw materials for the production of marketable P fertilizers. The process had a positive impact on the bioavailability of phosphorus and reduced the content of heavy metals in the obtained products. The P solubility in neutral ammonium citrate, an indicator of its bioavailability, was significantly raised from 19.7–45.7% in the raw ashes and 76.5–100% in the thermochemically treated SSA. The content of nutrients in the recyclates was in the range of 15.7–19.2% P2O5, 10.8–14.2% CaO, 3.5–5.4% Na2O, 2.6–3.6% MgO and 0.9–1.3% K2O. The produced fertilizer raw materials meet the Polish norms for trace elements covered by the legislation: the content of lead was in the range 10.2–73.1 mg/kg, arsenic 4.8–22.7 mg/kg, cadmium 0.9–2.8 mg/kg and mercury <0.05 mg/kg. Thus, these products could be potentially directly used for fertilizer production. This work also includes an analysis of the possibilities of using ashes for fertilizer purposes in Poland, based on the assumptions indicated in the adopted strategic and planning documents regarding waste management and fertilizer production. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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37 pages, 7221 KiB  
Article
Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy Balance
by Kacper Świechowski, Martyna Hnat, Paweł Stępień, Sylwia Stegenta-Dąbrowska, Szymon Kugler, Jacek A. Koziel and Andrzej Białowiec
Energies 2020, 13(12), 3161; https://0-doi-org.brum.beds.ac.uk/10.3390/en13123161 - 18 Jun 2020
Cited by 11 | Viewed by 3727
Abstract
Sustainable solutions are needed to manage increased energy demand and waste generation. Renewable energy production from abundant sewage sludge (SS) and digestate (D) from biogas is feasible. Concerns about feedstock contamination (heavy metals, pharmaceuticals, antibiotics, and antibiotic-resistant bacteria) in SS and D limits [...] Read more.
Sustainable solutions are needed to manage increased energy demand and waste generation. Renewable energy production from abundant sewage sludge (SS) and digestate (D) from biogas is feasible. Concerns about feedstock contamination (heavy metals, pharmaceuticals, antibiotics, and antibiotic-resistant bacteria) in SS and D limits the use (e.g., agricultural) of these carbon-rich resources. Low temperature thermal conversion that results in carbonized solid fuel (CSF) has been proposed as sustainable waste utilization. The aim of the research was to investigate the feasibility of CSF production from SS and D via torrefaction. The CSF was produced at 200~300 °C (interval of 20 °C) for 20~60 min (interval 20 min). The torrefaction kinetics and CSF fuel properties were determined. Next, the differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) of SS and D torrefaction were used to build models of energy demand for torrefaction. Finally, the evaluation of the energy balance of CSF production from SS and D was completed. The results showed that torrefaction improved the D-derived CSF’s higher heating value (HHV) up to 11% (p < 0.05), whereas no significant HHV changes for SS were observed. The torrefied D had the highest HHV of 20 MJ∙kg−1 under 300 °C and 30 min, (the curve fitted value from the measured time periods) compared to HHV = 18 MJ∙kg−1 for unprocessed D. The torrefied SS had the highest HHV = 14.8 MJ∙kg−1 under 200 °C and 20 min, compared to HHV 14.6 MJ∙kg−1 for raw SS. An unwanted result of the torrefaction was an increase in ash content in CSF, up to 40% and 22% for SS and D, respectively. The developed model showed that the torrefaction of dry SS and D could be energetically self-sufficient. Generating CSF with the highest HHV requires raw feedstock containing ~15.4 and 45.9 MJ∙kg−1 for SS and D, respectively (assuming that part of feedstock is a source of energy for the process). The results suggest that there is a potential to convert biogas D to CSF to provide renewable fuel for, e.g., plants currently fed/co-fed with municipal solid waste. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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24 pages, 16850 KiB  
Article
Co-Combustion of Municipal Sewage Sludge and Biomass in a Grate Fired Boiler for Phosphorus Recovery in Bottom Ash
by Andreas Nordin, Anna Strandberg, Sana Elbashir, Lars-Erik Åmand, Nils Skoglund and Anita Pettersson
Energies 2020, 13(7), 1708; https://0-doi-org.brum.beds.ac.uk/10.3390/en13071708 - 03 Apr 2020
Cited by 15 | Viewed by 2688
Abstract
Phosphorus has been identified as a critical element by the European Union and recycling efforts are increasingly common. An important phosphorus-containing waste stream for recycling is municipal sewage sludge (MSS), which is used directly as fertilizer to farmland. However, it contains pollutants such [...] Read more.
Phosphorus has been identified as a critical element by the European Union and recycling efforts are increasingly common. An important phosphorus-containing waste stream for recycling is municipal sewage sludge (MSS), which is used directly as fertilizer to farmland. However, it contains pollutants such as heavy metals, pharmaceutical residues, polychlorinated bi-phenyls (PCBs) and nano-plastics. The interest in combustion of MSS is continuously growing, as it both reduces the volume as well as destroys the organic materials and could separate certain heavy metals from the produced ashes. This results in ashes with a potential for either direct use as fertilizer or as a suitable feedstock for upgrading processes. The aim of this study was to investigate co-combustion of MSS and biomass to create a phosphorus-rich bottom ash with a low heavy metal content. A laboratory-scale fixed-bed reactor in addition to an 8 MWth grate-boiler was used for the experimental work. The concentration of phosphorus and selected heavy metals in the bottom ashes were compared to European Union regulation on fertilizers, ash application to Swedish forests and Swedish regulations on sewage sludge application to farmland. Element concentrations were determined by ICP-AES complemented by analysis of spatial distribution with SEM-EDS and XRD analysis to determine crystalline compounds. The results show that most of the phosphorus was retained in the bottom ash, corresponding to 9–16 wt.% P2O5, while the concentration of cadmium, mercury, lead and zinc was below the limits of the regulations. However, copper, chromium and nickel concentrations exceeded these standards. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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Review

Jump to: Research

20 pages, 3959 KiB  
Review
A Review on Management of End of Life Tires (ELTs) and Alternative Uses of Textile Fibers
by Panagiotis Grammelis, Nikolaos Margaritis, Petros Dallas, Dimitrios Rakopoulos and Georgios Mavrias
Energies 2021, 14(3), 571; https://0-doi-org.brum.beds.ac.uk/10.3390/en14030571 - 22 Jan 2021
Cited by 47 | Viewed by 6756
Abstract
Annually, approximately 3 billion tires are commercially transacted worldwide each year and an equivalent amount is disposed of by the end of their life. Despite the increase in the life of tires and the global economic and pandemic crisis, the number of discarded [...] Read more.
Annually, approximately 3 billion tires are commercially transacted worldwide each year and an equivalent amount is disposed of by the end of their life. Despite the increase in the life of tires and the global economic and pandemic crisis, the number of discarded tires is going to rise further due to the increasing demand for vehicles worldwide (approximately 5 billion tires by the end of 2030). The obsolete methods of tire disposal, including landfill, burning, etc., are a responsible for environmental issues (harmful substances production, air and soil pollution) and for the transmission of various diseases. Nowadays, approximately 70% of the total tires at the end of their life (ELTs) is recovered. The largest percentage of the recovered ELTs is intended for energy production or recovery as a fuel in cement industries or can be used for the production of various materials. A significant amount (approximately 95%) of the discarded ELTs can be reused. The products from the processing of ELTs can be fragments of different sizes and types, including: Trimmed rubber (70% by weight), steel wire (5–30% by weight), and fluff or textile fibers (up to 15% by weight). From the aforementioned materials, rubber and steel wires are mainly recovered and used for numerous applications. However, current ways of utilizing these materials will have to adapt or change in the near future, in order to comply with stricter regulations. The purpose of the current study is to sufficiently review recent progress on the management of ELTs, focusing on alternative uses of textile fibers such as additive for sound absorbing materials, bituminous conglomerates, concrete production, plastic materials, soil reinforcement, etc. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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22 pages, 4886 KiB  
Review
A Systematic Literature Review of Reverse Logistics of End-of-Life Vehicles: Bibliometric Analysis and Research Trend
by Meiling He, Tianhe Lin, Xiaohui Wu, Jianqiang Luo and Yongtao Peng
Energies 2020, 13(21), 5586; https://0-doi-org.brum.beds.ac.uk/10.3390/en13215586 - 26 Oct 2020
Cited by 19 | Viewed by 3072
Abstract
Under the background of the prompt development of the global economy and continuous improvement of environmental protection awareness, end-of-life vehicles (ELVs), as an essential part of “urban mineral”, have the substantial economic, resource, and environmental value. The research on reverse logistics of ELVs [...] Read more.
Under the background of the prompt development of the global economy and continuous improvement of environmental protection awareness, end-of-life vehicles (ELVs), as an essential part of “urban mineral”, have the substantial economic, resource, and environmental value. The research on reverse logistics of ELVs has developed rapidly, but the existing relevant reviews are based on unique research perspectives and do not fully understand the whole field. This work aims to help comprehend the research status of reverse logistics of ELVs, excavate and understand the critical publications, and reveal the main research topics in the past 20 years. Based on 299 articles published in ISI Web of Science Core Collection (WOSCC) database from 2000 to 2019, this paper uses the methodologies of literature bibliometrics and content analysis, combined with VOS viewer, CiteSpace, and Bibexcel software. Besides, the literature quantity and cited situation, core journals, distribution of countries and regions, institutions, core authors, subject categories, and keywords information are analyzed to determine the primary trends and future research hot spots focus on reverse logistics of ELVs. Full article
(This article belongs to the Special Issue Materials Recycling and Energy Use of Waste)
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