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A comprehensive review on pyrolysis from the circular economy point of view and its environmental and social effects
Abstract
The rising volume of waste created worldwide due to industrialization and commercial activity necessitates a method of waste management that is both effective and efficient. However, waste management is linked to unsustainable patterns in a linear economic system. On the contrary, a circular economy (CE) is widely perceived to solve various issues, including resource scarcity and long-term economic benefits. Utilizing pyrolysis to convert waste to energy and valuable compounds is a potential method for reducing waste while producing valuable end products. The current article offers a thorough analysis of pyrolysis from a circular economy point of view. First, the nature of pyrolysis is briefly described to understand subsequent concepts better. In the following, the pyrolysis of three types of waste, including tire, plastic, and biomass, is deeply investigated from the CE aspect. Then, the social and environmental impacts of pyrolysis from the life cycle assessment (LCA) perspective in developed and developing countries are scrutinized. In the end, ongoing challenges and suggestions for future research are also discussed. Pyrolysis products have not yet been standardized for trade in the market. However, pyrolysis might be able to close the loop of energy and materials. Also, LCA results revealed that pyrolysis has acceptable environmental impacts and a low global warming potential (GWP).
... The recycling market size is projected to reach a valuation of USD 8.32 billion by 2032. [30][31][32][33][34] The quantification and description of recycling processes can vary depending on the type and quality of the waste materials, the methods and technologies used, and the intended outcomes and benefits of recycling. 30 The recycling and reuse of WTR is an essential and permanent solution to the waste tire disposal problem. ...
... In recent years, the research on developing new methods for recycling WTR has attracted immense interest from social, economic and environmental aspects also. The life cycle assessment (LCA) of tire studied the environmental and economic impacts of recycling of tire with various waste management processes like landfilling, incineration etc. 31,33 Life cycle assessment (LCA) of tire is a method that evaluates the environmental impacts of life cycle of tire starting from its raw material preparation, production, transportation, use and its disposal. The process measures the energy consumption, greenhouse gas emissions, water use, resource depletion, and other environmental indicators associated with different waste management scenarios of waste tire. ...
... Furthermore, it estimates the costs and benefits of recycling, such as the savings in raw materials, energy, and landfill space, or the revenues from selling recycled products. 31 China is majorly involved in green tire disposal projects. One such major program is ZC Rubber Tire Recycling. ...
The recycling of waste vulcanized rubber (WVR) products is highly challenging due to the presence of a three-dimensional (3D) sulfur crosslinked network hindering the natural degradation process. Traditional disposal approaches such as combustion, stockpiling, and landfilling create several environmental concerns by generating toxic fumes and gases causing serious health issues. The best approach to resolve these problems is to reuse/recycle waste materials using sustainable methods for minimizing the negative impact of the current waste handling systems. The recycling of WVR products requires the breaking of the 3D crosslinked sulfur network using environmentally benign devulcanization and/or depolymerization strategies. Pyrolysis is another important process to recycle the WVR products into value-added chemicals. It is important to adopt sustainable approaches to recycle the WVR products into new products. The present review covers various sustainable technologies with the state-of-the-art development of recycling of waste tire and non-tire rubber products. Important processes such as physical, chemical, and biological devulcanization methods involving selective carbon–sulfur (C–S) and sulfur–sulfur (S–S) bond breakage along with depolymerization and pyrolysis are also discussed.
... After modification enhanced SA which was 59.23 m 2 g −1 23 Auricularia auricular dreg 400 Cetyl trimethyl ammonium bromide Cr (IV) ...
... Acid treatment modifies the physicochemical attributes of biochar to increase the adsorption capacities for the elimination of inorganic and organic pollutants from soil and wastewater. The pickling mechanism decreased the sludge-based adsorbent's micro-pore volume and enhanced the mesoporous volume, thereby improving the sorption capacity of biochar for antibiotics and heavy metals 23 . Compared to fresh biochar, H 3 PO 4 -treated eucalyptus-derived biochar exhibited higher removal efficiency of chromium hexavalent 24 . ...
... Moreover, amination and carboxyl groups modification of adsorbent also greatly increased Cu 2+ adsorption by powerful surface complexation with NH 2 -functional groups, which were greatly selective and slightly affected via competing cation 32 . KOH-treated biochar significantly increased its adsorption capacity to As (V) due to the enhancement of pore volume and surface area and the alternation of surface functional groups 23 . Elimination of organic contaminants could be increased through π-π EDA interaction between aromatic rings of pollutants and biochar 13 . ...
The pollution of soil and aquatic systems by inorganic and organic chemicals has become a global concern. Economical, eco-friendly, and sustainable solutions are direly required to alleviate the deleterious effects of these chemicals to ensure human well-being and environmental sustainability. In recent decades, biochar has emerged as an efficient material encompassing huge potential to decontaminate a wide range of pollutants from soil and aquatic systems. However, the application of raw biochars for pollutant remediation is confronting a major challenge of not getting the desired decontamination results due to its specific properties. Thus, multiple functionalizing/modification techniques have been introduced to alter the physicochemical and molecular attributes of biochars to increase their efficacy in environmental remediation. This review provides a comprehensive overview of the latest advancements in developing multiple functionalized/modified biochars via biological and other physiochemical techniques. Related mechanisms and further applications of multiple modified biochar in soil and water systems remediation have been discussed and summarized. Furthermore, existing research gaps and challenges are discussed, as well as further study needs are suggested. This work epitomizes the scientific prospects for a complete understanding of employing modified biochar as an efficient candidate for the decontamination of polluted soil and water systems for regenerative development.
... One of the most significant advantages of pyrolysis is its flexibility in terms of output and its capacity to process a wide variety of plastics, including those that are not easily recycled through mechanical means [88,98]. Despite these benefits, pyrolysis is a capital-intensive process, requiring precise control to ensure optimal energy efficiency and minimize environmental impacts [99]. Gasification represents another advanced technology for energy recovery from plastic waste. ...
... Gasification represents another advanced technology for energy recovery from plastic waste. Through partial oxidation at high temperatures, plastic is converted into syngas a mixture of hydrogen and carbon monoxide that can be utilized for electricity generation, heating, or as a feedstock for chemical production [99]. Gasification generally exhibits higher energy efficiency than incineration, with efficiencies ranging from 45 to 65%, depending on the process parameters and the type of plastic waste [100]. ...
Energy generation from plastic composites offers a viable solution to the dual challenges of plastic waste management and renewable energy production. This study explores the potential of plastic composites for energy generation through key waste-to-energy technologies, including incineration, pyrolysis, gasification, and anaerobic digestion. The study employs a Systematic Literature Review (SLR) methodology, following the PRISMA guidelines, and draws from two primary databases: ScienceDirect and Web of Science. Each method is assessed in terms of energy efficiency, environmental impact, economic feasibility, and scalability, based on studies published between 2020 and the second quarter of 2024. Pyrolysis and gasification emerge as particularly promising technologies due to their flexibility and higher energy recovery potential. Incineration, although widely used and well-established, presents challenges related to emissions, despite improvements in emissions control technologies. Anaerobic digestion, though limited in its application to conventional plastics, provides sustainability benefits when used with biodegradable materials. The analysis reveals regional disparities in research focus, the influence of policy frameworks, and the need for technological innovation to optimize these processes. Ultimately, the findings highlight the importance of integrating energy recovery from plastic waste within circular economy models to achieve sustainable waste management and renewable energy goals.
... From the point of view of the circular economy, recycling already generates organic waste, and converting these into useful resources is one of the ways to alleviate such constraints ( Figure 9). In this case, so-called closed-loop recycling (reusing and recycling used items to produce energy through pyrolysis) can be classified as closed-loop energy [63]. The shortage of natural resources, especially so-called non-renewable energy resources, is a problem in modern society. ...
... (Figure 9). In this case, so-called closed-loop recycling (reusing and recycling used items to produce energy through pyrolysis) can be classified as closed-loop energy [63]. ...
Organic waste-to-energy (OWtE) technologies are playing a steadily increasing role in the Green Transition, thus becoming a powerful driver in the establishment of an ever more efficient and sustainable circular economy. The advantages of OWtE processes are well known: not only do they reduce the waste volumes sent to landfills or incineration plants, but also and foremost, through the energy they yield (biogenic carbon dioxide, amongst others), they reduce dependance on fossil fuels. This article gives a complete panorama of these technologies, starting from the classical methods and ending with a review of the latest modern novelties. Advantages and disadvantages of each method are highlighted, with particular focus on the formation of by-products and the relevant treatment aimed at preventing environmental pollution. Accordingly, modern techniques for increasing waste-to-energy efficiency and integrating the concept of circular economy and substitutability are analyzed from this perspective. Along with an analysis of modern scientific achievements in this area, practical examples of the implementation of technologies in European countries are given, with an emphasis on the obvious advantages, both economic and environmental.
... Densified RDF (d-RDF) is more manageable, facilitating better flowability when used as feedstock in thermochemical W2E technologies [16]. Production of different types of RDF is shown in Fig. 2. The pyrolysis process is generally an applicable and economically effective approach to convert various mixed feedstocks, such as d-RDF into high-value added products, including H 2 gas [18], commodity chemicals [19], and carbon-rich solid residue [20]. This process takes place in an oxygen-free or N 2 atmosphere at temperatures ranging from 300 to 700 • C [13,18,20]. ...
... Production of different types of RDF is shown in Fig. 2. The pyrolysis process is generally an applicable and economically effective approach to convert various mixed feedstocks, such as d-RDF into high-value added products, including H 2 gas [18], commodity chemicals [19], and carbon-rich solid residue [20]. This process takes place in an oxygen-free or N 2 atmosphere at temperatures ranging from 300 to 700 • C [13,18,20]. As a result, waste pyrolysis commonly yields three major products: pyrolytic gas, pyrolytic oil, and pyrolytic char. ...
The conversion of municipal solid waste (MSW) into its energy-rich fraction, known as refuse-derived fuel (RDF), addresses both MSW management and energy demand. RDF comprises a diverse blend of various non-hazardous waste streams, making it challenging to predict physical properties and chemical compositions. However, densification can help overcome these challenges. This work aims to explore the effect of densification degree on kinetic and thermodynamic parameters during the degradation of densified refuse-derived fuels (d-RDFs) in inert atmosphere. Herein, three d-RDFs samples obtained with varying degrees of densification and die temperatures ranging from 55 °C to 118 °C, as well as a mixed fines (MF) sample produced during the pelletization process, were analyzed. Pyrolysis potential of d-RDFs and MF were determined using thermogravimetric analysis in the temperature range from 30 to 800 °C, at multiple heating rates of 5, 10, and 20 K min−1. The effect of the degree of densification on physical characteristics, and kinetic and thermodynamic parameters of d-RDF was investigated. Apparent activation energy (Eα) was estimated employing Friedman (FR), Kissinger-Akahera-Sunnose (KAS), and Flynn-Wall-Ozawa (FWO) methods. Derived Eα values were used to determine the pre-exponential factor (Aα) using the Kissinger method. Experimental results revealed that the durability of d-RDFs increased from 79.26 % to 98.73 % as the densification degree increased from II to IX. Furthermore, the Eα values exhibited a decreasing trend in the first peaks of the DTG profiles, while an opposite trend was observed in the second peaks of DTG curves. However, with an increase in the degree of densification, the mean values of Eα decreased by 5–10 % for all methods. The Aα values, assessed using the FR method, surpassed the critical value of (109 s−1) for all samples. However, with the KAS and FWO methods, these values fell below (109 s−1) within the conversion range of 0.05–0.25. Thermodynamic parameters confirmed the endothermicity of the thermal degradation process.
... Pyrolysis distinguishes itself from incineration by recovering energy and materials more flexible through adjusting parameters like residence time, heating rate, and temperature [75]. Additionally, plastic pyrolysis has acceptable environmental effects with low global warming potential [11]. Pyrolysis of PP face mask waste can be regarded as an endothermic and non-spontaneous reaction [138]. ...
... Table 4 illustrates the differences between slow, fast, flash, and intermediate pyrolysis, depending on the heating rate, temperature, and residence time of the material being subjected to the process [9]. In addition, pyrolysis has other variations, including vacuum pyrolysis, catalytic pyrolysis, co-pyrolysis, microwave pyrolysis, and plasma pyrolysis, each of which differs based on the heat source, environment, and operating parameters used [11]. Numerous studies comparing it with other developing technologies to assess their viability have been done, and pyrolysis has lower operating costs than incineration [126,131,45]. ...
... Energy is largely responsible for the creation of modern civilization, but the global energy crisis has become a pressing concern for developing nations worldwide (Andooz et al., 2023). As the consumption of energy has increased drastically around the world because of industrialization, population growth, and economic expansion, it has become a global concern to supply the reliable energy in the modern era (Zaharia et al., 2019). ...
... According to Bangladesh Power Development Board (BPDB), 27% of country's installed power generation capacity is based on furnace oil. Bangladesh Petroleum Corporation (BPC) imported 4.4 and 6.23 million tones fuel oil, respectively for the year 2021 and 2022 and planned to import 7.72 million tones for the year 2023 which is 15 lakh tones higher than the previous year (Andooz et al., 2023). According to Bangladesh Bank, the country spent $5.3 billion and $8.9 billion, respectively for importing of petroleum products for the FY 2020-21 and 2021-21 (Hossain et al., 2023). ...
... A reasonable waste management system is needed due to globalisation and economic growth. In a linear economy, waste management is unsustainable, whereas a circular economy (CE) has the potential to address resource limitations and support ongoing economic growth [14,15]. The transition from traditional linear systems to circular economies emphasises the importance of innovative thinking and technology advancements in minimizing waste through the adoption of closed-loop systems and biorefineries [16]. ...
Lignocellulose biomass (LCB) gasification presents considerable opportunities for environmental conservation, energy crisis mitigation, and the advancement of the circular economy; nonetheless, its entire realisation is hindered by multiple obstacles. Comprehensive evaluation of different challenges is vital for enhancing the use of bioenergy. The study has identified sixteen obstacles and the analytical hierarchy process (AHP), frequently utilized in multiple criteria decision-making (MCDM), is applied to rank the obstacles that hinder the successful execution of LCB gasification. AHP is acknowledged for its ability to decompose multifaceted problems into an apparent hierarchical framework. The AHP theory is based on three core principles: decomposition, comparative evaluation and synthesis. The result of the study reveals that operational challenges are the most significant obstacle, weighing 0.1257, followed by gas cleaning at 0.1107, and the consolidation of initial funds, market establishment and harvesting and collection at 0.1037, 0.0913 and 0.0749, respectively. A strategic approach to LCB gasification advancement can foster global community well-being, drive economic development and improve energy access. This study seeks to provide a solution for researchers and stakeholders addressing energy scarcity and the challenges related to biomass gasification.
... Additionally, its production via pyrolysis generates valuable by-products, contributing to a more sustainable process. However, as highlighted by Andooz et al. (2023) [55], the current high costs of pyrolysis present a challenge. To make pyrolysis more economically viable, support from public and private institutions is needed to enhance the marketability of its products. ...
The growing concern over water pollution and waste management requires innovative solutions that promote resource efficiency within a circular economy. This study aims to utilize rice husk (RH) as a sustainable feedstock to develop highly porous silica particles and generate valuable by-products, addressing the dual challenges of waste reduction and water contamination. We hypothesize that optimizing the production of amorphous silica from acid-washed RH will enhance its adsorptive properties and facilitate the concurrent generation of bio-oil and syngas. Amorphous silica particles were extracted from acid-washed RH with a yield of 15 wt% using a combination of acid washing at 100 °C, pyrolysis at 500 °C, and calcination at 700 °C with controlled heating at 2 °C/min. The optimized material (RH2-SiO2), composed of small (60–200 nm) and large (50–200 µm) particles, had a specific surface area of 320 m2/g, with funnel-shaped pores with diameters from 17 nm to 4 nm and showed a maximum cadmium adsorption capacity of 407 mg Cd/g SiO2. Additionally, the pyrolysis process yielded CO-rich syngas and bio-oil with an elevated phenolic content, demonstrating a higher bio-oil yield and reduced gas production compared to untreated RH. Some limitations were identified, including the need for bio-oil upgrading, further research into the application of RH2-SiO2 for wastewater treatment, and the scaling-up of adsorbent production. Despite the challenges, these results contribute to the development of a promising adsorbent for water pollution control while enhancing the value of agricultural waste and moving closer to a circular economy model.
... Briefly, it is an alternative industry model that involves sharing, renting, reusing, repairing, refurbishing, and recycling materials and existing products as many times as possible to create added-value products [1]. According to Andooz et al. [2], this new business model is a designer based on economy and environment promoting development, profit, and environmental protection. Thus, most of the countries have started adopting several policies to promote the transition from a linear to a circular economy model, which will contribute to developing low-carbon (C) and resource-efficient economies by avoiding unsustainable resource consumption, product redundancy, waste, and pollution [3,4]. ...
The valorization of agricultural by-products represents a promising approach to sustainable development. In the transition toward a circular economy, Opuntia ficus indica peels (OFIP) can be converted into valuable products, thereby reducing greenhouse gas emissions and contributing to climate change mitigation. This study proposes the valorization of OFIP residues through pyrolysis, focusing on biochar production. The main objective of the present study is to optimize OFIP pyrolysis, considering both slow- and fast-pyrolysis processes at temperatures ranging from 500 to 700°C. Therefore, two different pyrolysis technologies were applied: fixed bed and spouted bed reactors for slow and fast pyrolysis, respectively. The novel approach of the study lies in employing the same biomass feedstock in two different pyrolysis technologies, enabling a direct comparison of the effects of these pyrolysis approaches on biochar production. Moreover, the resulting biochars underwent comprehensive characterization by elemental, proximate, chemical composition, and thermogravimetric (TG) analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), CO2 adsorption, and scanning electron microscopy (SEM). Additionally, the potential of the obtained biochar for subsequent valorization was evaluated, and the most suitable biochar for a specific application was determined based on its properties. The obtained results revealed that slow pyrolysis of OFIP yielded slightly higher biochar amounts than fast pyrolysis, with the highest biochar production at 500°C. Regarding biochar characterization, fast pyrolysis samples had higher fixed carbon and ash contents than the ones produced from slow pyrolysis. Moreover, fast-pyrolysis biochars showed a more developed porous structure, attaining a specific surface area of 328.61 m² g⁻¹ and a micropore volume of 0.13 cm³ g⁻¹ at 700°C. This study concluded that fast-pyrolysis biochars may be suitable for catalytic applications, whereas slow-pyrolysis biochars may be more appropriate for adsorption and soil applications. Nevertheless, the high ash content of the OFIP-derived biochar makes it unsuitable to be used for power generation.
Graphical abstract
... However, these processes require large amounts of energy and lead to waste formation and the release of halogenated compounds such as dioxins. Pyrometallurgical plants require particular infrastructure to prevent the release of dioxins and brominated flame retardants into the environment, which also increases the cost of the process [16][17][18]. ...
Electronic waste grows globally at a rate of 5% annually, which makes electronic waste recycling (WEEE recycling) an urgent task aimed at achieving (i) environmental protection and (ii) the preservation of mineral resources through the re-introduction of strategic metals into the market. As it turns out, WEEE recycling produces further waste, called WEEE secondary waste, which still contains valuable metals such as gold, silver, and copper. This study assessed the economic viability of recovering these metals and identified the most promising targets and approaches. WEEE secondary waste produced at a plant in southern Europe was sampled and examined for this purpose. The study methods included an ANOVA (analysis of variance) and an OCCP (orthogonal central composition plan). Over 90% gold, silver, and copper extraction was achieved with hydrochloric acid leaching in sodium hypochlorite with sodium chlorite as an oxidizing agent at 60 °C. The significance of the variation in the response for each factor, calculated using the Yates algorithm, demonstrates that by excluding sodium chloride and optimizing the doses of hydrochloric acid and sodium hypochlorite, gold can be selectively recovered through the leaching process. The scenario of HCl (2.5M)/NaClO (5%) leaching results in the maximum extraction effect of Au (91.6%) at the lowest concentrations of Ag and Cu (37–44%).
... The LCA methodology has been used to scrutinize the social and environmental impacts of pyrolysis in developed and developing countries (Andooz et al., 2023). In other works and more specifically, different options for the EoL tires including pyrolysis, energy recovery in cement plant, energy recovery in a dedicated incineration plant and production of infill have been compared by implementing LCA according to the relevant ISO standards with FU the treatment of one (1) tone of EoL tires, showing that material recycling including pyrolysis has lower environmental impacts (Maga et al., 2023). ...
... Due to this, much interest has been devoted to the development of autothermal oxidative pyrolysis as an alternative to energy neutrality (Huang et al., 2020). However, this process comes at the cost of reducing the production of biofuel products, whose recovery is one of the most attractive aspects of the process from the point of view of the circular economy (Andooz et al., 2023). Renewable energy sources represent a solution to this problem (Lobato-Peralta et al., 2021), and solar reactors are a green chemistry alternative. ...
... Next, the obtained powder was mixed with KOH (activated agent) at a mass ratio of 1:1, and after adding 50 ml of H 2 O, it was stirred for 40 min by a magnetic stirrer at 25 • C. The obtained mixture was placed in a vacuum oven to dry. After activation, pyrolysis was used to prepare porous and high surface area biochar [46]. The KOH-activated Heracleum Persicum seed was pyrolyzed under an N 2 atmosphere with a 10 • C/min heating rate and a 100 mL/min flow rate at 500 • C for 30 min. ...
... In circular economy terms, pyrolysis may be a noteworthy solution, which fits into the 3xR hierarchy (reduce, reuse, recycle). Pyrolysis is the process of decomposition of a complex molecule of a chemical compound under the influence of sufficiently high temperatures in an anaerobic environment [14,[17][18][19][20][21]. The pyrolysis process is represented by Reaction [22] (1): ...
This article discusses research on the low-temperature pyrolysis of waste floor and furniture joinery as an example of chemical recycling. Pyrolysis was carried out at 425 °C to obtain solid, liquid, and gaseous products. In line with the circular economy concept, the waste was transformed into economical and environmentally friendly raw materials suitable for application. Research results related to the chemical composition and properties of pyrolysis products are shown, with particular emphasis on the migration process of acidic impurities, i.e., sulphur and chlorine. In some processes, the presence of such substances can be a problem. Research has shown the high potential for sulphur and chlorine migration in pyrolysis products. It was shown that for woodwork, the most sulphur was discharged with the pyrolysis gas and the least was immobilised in the oil fraction. For vinyl panels, more than 50% of the sulphur was immobilised in the char. Chlorine was immobilised mainly in the char and pyrolysis gas. A high chlorine content of 12.55% was found in the vinyl panel. At the same time, a high chlorine content was also found in the pyrolysis products of these panels. This value is several times higher than in wood-based waste.
... The cost of pyrolysis highly depends on the type of pyrolytic reactor used. According to Andooz et al. [52], current waste treatment systems can economically benefit from the integration of pyrolytic processes for resource recovery (like pyrolytic oil production for usage in internal combustion engines, ethylene production, etc.). ...
The presented paper addresses two significant issues of the present time. In general, the studies of the effect of synthetic fuels on cavitation formation and cavitation erosion prediction in the nozzle tip of common-rail diesel injectors were addressed. The first problem is plastic waste, which can have a significant negative environmental impact if not treated properly. Most plastic waste has high energy value, so it represents valuable material that can be used in resource recovery to produce various materials. One possible product is synthetic fuel, which can be produced using thermal and catalytic pyrolysis processes. The first issue addressed in the presented paper is the determination of fuel properties since they highly influence the fuel injection process, spray development, combustion, etc. The second is the prediction of cavitation development and cavitation erosion in a common-rail diesel injector when using pyrolytic oils from waste plastic. At first, pyrolytic oils from waste high- and low-density polyethylene were obtained using thermal and catalytic pyrolysis processes. Then, the obtained oils were further characterised. Finally, the properties of the obtained oils were implemented in the ANSYS FLUENT computational program and used in the study of the cavitation phenomena inside an injection nozzle hole. The cavitating flow in FLUENT was calculated using the Mixture Model and Zwart-Gerber-Belamri cavitation model. For the modelling of turbulence, a realisable k–ε model with Enhanced Wall Treatment was used, and an erosion risk indicator was chosen to compare predicted locations of cavitation erosion. The results indicate that the properties of the obtained pyrolytic oils have slightly lower density, surface tension and kinematic viscosity compared to conventional diesel fuel, but these minor differences influence the cavitation phenomenon inside the injection hole. The occurrence of cavitation is advanced when pyrolytic oils are used, and the length of cavitation structures is greater. This further influences the shift of the area of cavitation erosion prediction closer to the nozzle exit and increases its magnitude up to 26% compared to diesel fuel. All these differences have the potential to further influence the spray break-up process, combustion process and emission formation inside the combustion chamber.
... A good review article published recently has demonstrated the role of pyrolysis from the circular economy point of view and its environmental and social effects Andooz et al. (2023). This shows that even with some limitations, the excellent advantages surpass the disadvantages, and pyrolysis is, to date, the most useful technique used in different countries and the base process for obtaining different carbon nanostructures Deng et al. (2016). ...
Plastic waste consumption increases exponentially every year, mainly in the last three years due to the COVID-19 pandemic. The rapid growth of plastic products has exceeded the world's capacity to deal with this type of trash. Thus, it has become a substantial environmental concern in modern society. Another dire concern is the improper disposal of used supercapacitors, leading to serious environmental impacts. Consequently, critical action to tackle this issue is to transform trash into high-valued materials, such as carbon nanomaterial supercapacitors. Considering several methodologies of recycling, pyrolysis stands out due to its simplicity and easy handling of mixed plastic waste to produce carbonaceous materials with different dimensions (0, 1, 2, and 3D). Thus, from this technology, it is possible to create new opportunities for using plastic waste and other types of waste to produce cheaper carbon-based materials for supercapacitors. This review aims to provide readers with a sustainability-driven view regarding the reutilization of plastic trash, discusses the environmental consequences of not doing so, and shows plastic waste solutions. Despite the broad scope of the topic, this review focuses on identifying the currently studied strategies to convert plastic waste into carbon-based electrodes, using less expensive and more efficient competitive protocols, besides emphasizing the diverse types (0, 1, 2, and 3D) of nanostructures. This review also proposes promising options for a sustainable cycle of plastic waste and supercapacitor.
... Owing to the large amount of plastic waste during the pandemic, different recovery methods were proposed. For instance, plastic waste such as masks can be utilized as a construction material (Rehman and Khalid 2021;Zhang et al. 2022;Zhang et al. 2023) and as an energy source (Dharmaraj et al. 2021;Jung et al. 2021;Andooz et al. 2023). ...
This study examines urban plastic waste generation using a citizen science approach in six Latin American countries during a global pandemic. The objectives are to quantify generation rates of masks, gloves, face shields, and plastic bags in urban households using online survey and perform a systematic cross-jurisdiction comparisons in these Latin American countries. The per capita total mask generation rates ranged from 0.179 to 0.915 mask cap⁻¹ day⁻¹. A negative correlation between the use of gloves and masks is observed. Using the average values, the approximate proportion of masks, gloves, shields, and single-use plastic bags was 34:5:1:84. We found that most studies overestimated face mask disposal rate in Latin America due to the simplifying assumptions on the number of masks discarded per person, masking prevalence rate, and average mask weight. Unlike other studies, end-of-life PPE quantities were directly counted and reported by the survey participants. Both of the conventional weight-based estimates and the proposed participatory survey are recommended in quantifying COVID waste. Participant’ perception based on the Likert scale is generally consistent with the waste amount generated. Waste policy and regulation appear to be important in daily waste generation rate. The results highlight the importance of using measured data in waste estimates.
... CE operates on the belief that the economy and environment can synergistically drive environmental preservation, cultivate innovative business models, and generate employment opportunities. CE is increasing as a focal point in academic research and organizational implementation [13]. ...
Considering sustainability and resource efficiency goals, the circular economy has gained significant attention as a promising economic model. To achieve this the countries worldwide are putting their attention on total municipal waste generation and its disposal methods with focus on recycling. For sustainable development of the country, policy makers need to design a new economic framework that should target reduction in the waste generation and enhancement in its reusage. Keeping in view this need the Organisation for Economic Cooperation and Development (OECD) explored twelve key factors associated with the circular economy for European countries. For better understanding Heat map analysis is done on total municipal waste generation and recycling for ten countries. The trend analysis is also performed to get insight into how countries should plan their future policy designs keeping sustainability in the limelight. The study employs an ARIMA model to predict trends in two crucial components of the circular economy: municipal waste generation and recycling rates. The predicting modelling approach will provide a targeted measures to policy makers to handle the waste efficiently.
The modification of the operational parameters of pyrolysis, such as the heating rate (HR), to produce adsorbent biochar (BC) has been little explored, especially regarding materials obtained from premodified biomass. Consequently, some fundamental aspects in this field remain not understood, which can limit more targeted syntheses of these materials in environmental application. This study investigated the effect of HR on the pyrolysis of sugarcane bagasse premodified with NaOH. BC was produced in a muffle furnace with HR of 5, 10, 15, or 20 °C min−1, at final temperature of 400 °C, and characterized by FTIR, N2 adsorption, SEM, EDS, conductometric titration, and determination of the point of zero charge. The methylene blue (MB) adsorption kinetics and equilibria on the produced materials were studied to elucidate the influence of HR on the adsorption. The results showed that the surface chemistry and physical properties of the materials were not influenced by different HR. However, equilibrium times for MB adsorption of 10 and 5 h were observed for HR of 5 and 10 °C min−1, respectively, while an equilibrium time greater than 48 h was observed for the highest HR; MB intraparticle diffusion played an important role in these different behaviors. The adsorption isotherms were better fit by the Konda model. The fitted parameters suggested that the distribution of sites within pores of different sizes was also determined by the HR. The results showed that the use of MB can help identify structural changes induced by pyrolysis parameters that have a minor effect on the properties of adsorbent BC, such as HR.
The environmental impact of petroleum-based plastic has had far-reaching repercussions for human health, global warming, and natural flora and fauna, particularly in the seas and marine life. The inability of synthetic plastics to biodegrade is the fundamental cause of environmental persistence. Comprehensive studies show that plastic remains in the environment for 20 to 50 years after being disposed of in various waste disposal systems. The global demand for bioplastics as a substitute for traditional plastics has increased due to their nontoxicity, biocompatibility, renewability, and biodegradability properties. This book chapter focuses on the possibilities for sustainable and eco-friendly bioplastic materials by investigating several agricultural waste sources. The thorough evaluation of different methods and materials gives significant insights for academics, scientists, and industry experts seeking to contribute to the expanding area of green materials. As we seek environmentally conscious solutions, using agricultural waste in bioplastics appears to be a viable option for lowering dependency on conventional plastics and building a more sustainable future.
The global increase in energy consumption, driven by population growth and improved living standards, has led to a heavy reliance on fossil fuels, causing significant environmental concerns. This has prompted a shift toward sustainable energy sources, with biomass, especially lignocellulosic forest biomass, emerging as a key alternative due to its abundance and carbon-neutral potential. Microwave-assisted pyrolysis (MAP) is an efficient method for converting forest biomass into valuable bioproducts and bioenergy with reduced energy use. This review introduces biomass types, focusing on forest biomass and its role in global energy production. It compares MAP to conventional pyrolysis, highlighting the benefits of rapid, uniform heating and improved product yields. Key operational conditions, such as temperature, microwave power, biomass size, and catalyst ratios, are discussed in relation to their impact on product quality and yield. Despite its advantages, MAP faces challenges, particularly in temperature control, which can affect bio-oil yield and quality. High temperatures may cause unwanted secondary reactions, while low temperatures can lead to incomplete decomposition. Research into biomass dielectric properties and process modeling is essential in order to optimize MAP and scale it up for industrial use. Addressing bio-oil quality issues through catalytic upgrading is also critical for broader adoption.
Considering sustainability and resource efficiency goals, the circular economy has gained significant attention as a promising economic model. For the country’s sustainable development, policymakers need to design a new economic framework that targets the reduction of waste generation and the enhancement of its usage. To achieve this, countries worldwide focus on total municipal waste generation and its disposal methods with a focus on recycling. Considering this need, the Organisation for Economic Co-operation and Development (OECD) explored twelve factors associated with the Circular Economy (CE) for European countries. For a better understanding, a correlation analysis was conducted on total municipal waste generation and recycling for eleven countries. Trend analysis is also performed to understand how countries should plan their future policy designs while keeping sustainability in the limelight. The study employs an autoregressive integrated moving average (ARIMA) model to predict trends in two crucial components of the CE: municipal waste generation and recycling rates. The predicting modelling approach will provide a targeted measure for policymakers to handle waste efficiently.
This work presents a methodology integrating Non-Linear Programming (NLP) for multi-objective and multi-period optimization, addressing sustainable waste management and energy conversion challenges. It integrates waste-to-energy (WtE) technologies such as Anaerobic Digestion (AD), Incineration (Inc), Gasification (Gsf), and Pyrolysis (Py), and considers thermochemical, technical, economic, and environmental considerations through rigorous non-linear functions. Using Mexico City as a case study, the model develops waste management strategies that balance environmental and economic aims, considering social impacts. A trade-off solution is proposed to address the conflict between objectives. The economical optimal solution generates 1.79M and reduces emissions by 54%, where 40% is due to gasification technology. Moreover, the environmentally optimal solution, with incineration and gasification generates 9500 MWh/day and 5960 MWh/day, respectively, demonstrates the capacity of the model to support sustainable energy strategies. Finally, this work presents an adaptable framework for sustainable waste management decision-making.
Pyrolytic synergistic interactions, in which the production of pyrolyzates is enhanced or inhibited, commonly occur during the co-pyrolysis of different polymeric materials, such as plastics and biomass. Although these interactions can increase the yield of desired pyrolysis products under controlled degradation conditions, the desired compounds must be separated from complex pyrolyzates and further purified. To balance these dual effects, this study was aimed at examining pyrolytic synergistic interactions during slow heating co-pyrolysis of biodegradable plastics including polylactic acid (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexaoate) (PHBH) and petroleum-based plastics including high-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS). Comprehensive investigations based on thermogravimetric analysis, pyrolysis–gas chromatography/mass spectrometry, and evolved gas analysis-mass spectrometry revealed that PLA and PHBH decompose at lower temperatures (273–378 °C) than HDPE, PP, and PS (386–499 °C), with each polymer undergoing independent decomposition without any pyrolytic interactions. Thus, the independent pyrolysis of biodegradable plastics, such as PLA and PHBH, with common plastics, such as HDPE, PP, and PS, can theoretically be realized through temperature control, enabling the selective recovery of their pyrolyzates in different temperature ranges. Thus, pyrolytic approaches can facilitate the treatment of mixed biodegradable and common plastics.
Research background: The concept of sustainable firm performance has gained significant interest within the highly competitive usiness arena. There has been a significant increase in the adoption and implementation of circular economy practices by industries. If a company can implement an established approach to circular economy practices, it may expedite the attainment of sustainable corporate performance. This research is conducted in the context of ready-made garment organizations that are following green criteria in their business activities. The study focuses on an emerging South Asian country, Bangladesh, as it holds a strong
position in the global apparel and garment market; it is imperative to assess and ensure the environmental maintenance of this country’s garment sector.
Purpose of the article: The purpose of this research is to investigate the relationship between circular economy practices and sustainable organizational performance. The study focuses on the contributory relationship of circular economy practices on three-dimensional sustainable performance, i.e. on environmental, financial, and social performance.
Method: This is a quantitative survey-based study; a total of 418 managers were selected to
participate. Primary data was collected through a structured questionnaire given to a sample of permanent managers of green garment organizations in Bangladesh. For data input and
analysis, SPSS and PLS-SEM software were used.
Findings & value added: The results of our study demonstrate a noteworthy relationship between circular economy practices and sustainable performance. This research enhances our
comprehension of the efficacy of circular economy practices in addressing environmental issues. The study examines the potential ramifications of implementing circular economy practices for policymakers in the green garment sector, which is known for its significant labor-intensive activities, and ranks as the country's second-largest contributor. The outcomes provide a distinctive perspective for adding value to the environmental concerns in emerging economies. Thus, through an investigation of circular economy practices, our research provides valuable insights for the market of global garment products concerning the environment,
resource maximization, energy saving, and circular production processes.
This report, the third in the series by New Zealand's Chief Science Advisor to the Prime Minister, outlines how we might capture value from food loss and waste (FLW) before it ends up in landfills. It covers upcycling, animal feed, material recovery, nutrient recovery, energy recovery, and disposal. The report explores technologies and approaches that facilitate value capture from FLW, but also highlights that a lack of knowledge on the composition of our FLW streams presents a challenge to systematically capturing value. The report concludes by acknowledging the tension between capturing value in the near team and avoiding FLW in the long term but seeks to resolve this tension through recommendations to the government that highlight that the problem is big enough for multiple solutions at different scales.
The substantial rise in global energy demand, propelled by industrial expansion, population growth, and transportation needs, poses a formidable challenge. The concurrent urbanization places pressure on the disposal of solid municipal solid waste and the management of plastic waste. Addressing the global waste crisis requires innovative and sustainable garbage disposal solutions with an environmentally friendly approach. This review tackles the challenges of worldwide waste management, focusing on renewable and sustainable fuels and waste recycling through the exploration of co‐pyrolysis as an innovative method. It explores the characteristics and environmental impact of municipal solid waste (MSW) and plastic waste (PW), delving into pyrolysis fundamentals, processes, and challenges. The primary emphasis is on co‐pyrolysis, elucidating its integration of municipal and plastic waste, synergistic effects, and advantages. The manuscript thoroughly analyzes reaction kinetics, thermodynamics, and the feasibility of co‐pyrolysis for energy recovery. It also delves into the synthesis of renewable fuels and valuable chemical intermediates, considering optimization of product distribution. Environmental and economic sustainability aspects, including impact assessment, greenhouse gas emissions, life cycle analysis, and cost analysis of co‐pyrolysis processes, are comprehensively investigated. The review underscores the economic benefits of renewable fuel and chemical materials synthesis. The conclusion addresses challenges, proposes future directions, outlines limitations, technical challenges, environmental considerations, and recommends further exploration and integration with other waste management techniques. The manuscript emphasizes the ongoing importance of research in this critical field, aiming to contribute to the development of effective solutions for the escalating global waste management crisis.
The rapid urbanization witnessed in developing countries in Asia and Africa has led to a substantial increase in municipal solid waste (MSW) generation. However, the corresponding disposal strategies, along with constraints in land resources and finances, compounded by unorganized public behaviour, have resulted in ineffective policy implementation and monitoring. This lack of systematic and targeted orientation, combined with blind mapping, has led to inefficient development in many areas. This review examines the key challenges of MSW management in developing countries in Asia and Africa from 2013 to 2023, drawing insights from 170 academic papers. Rather than solely focusing on recycling, the study proposes waste sorting at the source, optimization of landfill practices, thermal treatment measures, and strategies to capitalize on the value of waste as more pertinent solutions aligned with local realities. Barriers to optimizing management systems arise from socio-economic factors, infrastructural limitations, and cultural considerations. The review emphasizes the importance of integrating the study area into the circular economy framework, with a focus on enhancing citizen participation in solid waste reduction and promoting recycling initiatives, along with seeking economic assistance from international organizations.
Waste Tyres (WT) are a significant fraction of industrial waste and a source of environmental hazards with limited valorisation. To reduce this problem, currently there is a growing interest in valuing the WT through pyrolysis to obtain multifunctional liquids to improve the rheological and self-healing properties of aged binders. This research provides a comprehensive study on using WT mixtures as precursors for asphalt rejuvenators by means of pyrolysis and distillation processes. To this end, WT polymeric fractions from light (WT-L) and mining trucks (WT-M) were used as feedstock and characterised for compositional and thermal properties. Additionally, micropyrolysis coupled with gas chromatography/mass spectrometry (Py-GC-MS) was used to identify the major products in pyrolysis vapours, to elucidate the reaction maps describing thermal degradation of WTs and to predict the feasible reaction conditions. The pyrolysis liquids were produced after a screening of reaction conditions and subjected to distillation, following a response surface model to produce an optimised pyro-rejuvenator. The results showed that the pyrolytic rejuvenator obtained through pyrolysis at 465 °C and distillation cutting at 160-200 °C is mainly composed of hydrocarbons and aromatic substances (95.5%), with a significant proportion of limonene (33.71%). Furthermore, the pyrolytic rejuvenator exhibited highly desirable physical properties in the context of its application and excellent oxidative stability (85.7%). Otherwise, it was determined that bitumen mixtures with 3% to 6% doses of pyro-rejuvenator improved the viscosity, softening point, and penetration of aged binders, restoring their physical properties to the virgin state. In conclusion, pyro-rejuvenators can be successfully used as a promising solution to produce more durable and sustainable pavements with improved rheological and healing properties.
The investigation of environmentally friendly substitutes for conventional jet fuels has been motivated by the aviation industry’s negative environmental effects, particularly those caused by greenhouse gas emissions. As a potential answer, bio-jet fuels (BJFs) made from sustainable feedstocks have gained popularity. In order to compare the environmental performance of bio-jet fuel to that of traditional fossil-based jet fuel, this study does a thorough life cycle assessment (LCA). The LCA framework takes into account every stage of the manufacture of bio-jet fuel, from feedstock cultivation through final application in aircraft engines. To estimate the environmental impacts throughout multiple life cycle stages, data from numerous sources are combined, including literature, industry reports, and databases. The possibility for global warming, energy use, water use, eutrophication, and land use change are among the environmental factors evaluated. The LCA’s first findings show that producing bio-jet fuel typically results in fewer net carbon dioxide emissions than producing conventional jet fuel. The production of biofuel feedstocks and their processing has an impact on things like land use change and agricultural inputs. However, the ability of feedstock crops to store carbon and the adoption of more environmentally friendly agricultural methods frequently mitigate these effects. A lower overall energy consumption during the life cycle of bio-jet fuel is also a result of the reduced reliance on fossil fuels. Water utilization is a crucial factor to take into account, with some biofuel manufacturing methods using more water than traditional jet fuel refining. The study assesses methods to improve the overall sustainability of the manufacturing of bio-jet fuel and lessen its effects on the environment. This LCA seeks to provide light on the environmental trade-offs related to the adoption of bio-jet fuel through a comparative examination of several bio-jet fuel production pathways and feedstock sources. The findings will help stakeholders in the aviation industry make well-informed judgments about the viability and sustainability of integrating bio-jet fuels. Life cycle assessment carried out in this chapter emphasizes the potential of bio-jet fuel to lessen the environmental impact of the aviation sector. The practicality of bio-jet fuels as a crucial part of a more sustainable aviation future is anticipated to be further enhanced by continuous research and technology improvements, even though challenges regarding feedstock farming practices and water utilization still exist.
E-waste is a major global problem linked to the use, and discard of, electronic and electric devices. While the volume of these obsolete devices continues to increase and accumulate, the means and approaches currently used to reuse, dispose of, recycle, and address this continues to vary widely in terms of availability, effectiveness, and value. The issues relating to e-waste management include those emanating from managerial, environmental, labor, and health perspectives. This article aims to present an overview of the key considerations related to the e-waste dilemma, and also proposes issues, challenges, and solutions to addressing the problem. A focus on the factors and variables affecting e-waste management, together with a global framework of e-waste management methods and strategies, are then followed by recommendations and viable areas for future research.
The lifecycle assessment (LCA) framework is widely applied to comprehensively evaluate and improve the environmental performance of a circular economy (CE). The advances and application of LCA has been primarily restricted to evaluate the environmental performance of the CE at a micro-level, wherein the CE is implemented for a single product system. However, the CE can be operationalized at two broader levels: the meso-level (for eco-industrial parks) and the macro-level (for a city, state, or nation). Six methodological challenges emerge when applying LCA to a meso-or macro-level CE and remain unaddressed in the existing literature. This includes: selecting a relevant system boundary and functional unit, addressing data paucity and uncertainty, accounting for stakeholder behavior, assessing the trade-offs from renewable energy (RE) use, accounting for manufacturing and technology evolution, and quantifying displacement and rebound. This article proposes potential solutions and research priorities to address the above challenges.
Water makes up most of the Earth, although just 0.3% is usable for people and animals. The huge oceans, icecaps, and other non-potable water resources make up the remaining 99.7%. Water quality has declined in recent decades due to pollution from population growth, industry, unplanned urbanization, and poor water management. The textile industry has significant global importance, although it also stands as a major contributor to wastewater generation, leading to water depletion and ecotoxicity. This issue arises from the extensive utilization of harmful chemicals, notably dyes. The main aim of this review article is to combine and assess the impacts of textile wastewater that contains dyes and chemicals, and to examine their potential consequences on human health, aquatic health, and the environment. Moreover, the dedicated section presents an in-depth review of various environmentally sustainable approaches for the management and treatment of wastewater in the textile industry. These approaches encompass bio adsorbents, biological methods, membrane technology, ion exchange, advanced oxidation processes, as well as physicochemical and biochemical processes. Furthermore, this study also evaluates the contemporary progressions in this particular domain, taking into account the corresponding advantages and disadvantages. Finally, this article highlights the significance of recovering and reusing dyes, alkalis, and electrolytes in wastewater treatment. Additionally, it emphasizes the necessity of performing technoeconomic analyses and life cycle assessments (LCA) on wastewater treatment plants.
The increasing emissions of gaseous pollutants of anthropogenic origin, such as carbon dioxide (CO2), which causes global warming, have raised great interest in developing and improving processes that allow their mitigation. Among them, adsorption on porous materials has been proposed as a sustainable alternative. This work presents a study of CO2 equilibrium adsorption at low temperatures (0, 10, and 20 °C) over a wide range of low pressures, on activated carbon derived from Eucalyptus (ES) and Patula pine (PP) forest waste, and carbonaceous material derived from waste tires (WT). The precursors of these materials were previously prepared, and their physicochemical properties were characterized. ES and PP were thermochemically treated with phosphoric acid, and WT was oxidized with nitric acid. Additionally, these materials were used to obtain monoliths using uniaxial compaction techniques and different binding agents, with better results obtained with montmorillonite. A total of six adsorbent solids had their textural and chemical properties characterized and were tested for CO2 adsorption. The highest specific surface area (1405 m² g⁻¹), and micropore properties were found for activated carbon derived from Eucalyptus whose highest adsorption capacity ranged from 2.27 mmol g⁻¹ (at 0 °C and 100 kPa) to 1.60 mmol g⁻¹ (at 20 °C and 100 kPa). The activated carbon monoliths presented the lowest CO2 adsorption capacities; however, the studied materials showed high potential for CO2 capture and storage applications at high pressures. The isosteric heats of adsorption were also estimated for all the materials and ranged from 16 to 45 kJ mol⁻¹ at very low coverage explained by the energetic heterogeneity and weak repulsive interactions among adsorbed CO2 molecules.
This study addressed the development of a pilot plant for pyrolysis of scrap tires to obtain carbon black and other byproducts. The work was motivated by the goal of contributing to the development and dissemination of knowledge about existing technologies that allow modern economies to transform waste into valuable products, by documenting and discussing an empirical application in Brazil. Thispaper describes the development of a market for steel scrap, pyrolytic oil and carbon black products obtained from a vacuum pyrolysis process. The research work was conducted in Brazil, and was guided by the twofold purpose of reducing the environmental impacts, while gaining economical sustainability. Modern economies increasingly need to devise strategies to address energy generation while preserving natural ecosystems. These strategies include leveraging the use of renewable energy sources. Acknowledging that scrap tires hold an enormous potential as a sustainable energy option, this study aimed to contribute to the development and maturity of eco-friendly processing approaches to realize its full potential. The work involved a preliminary phase concerned with the operation of vacuum pyrolysis of scrap tires at a laboratorial scale, followed by the design of the pilot plant that operated for 10 years, at the time of the study, with a 100 kg/h batch flow. Results show that the yield of the pyrolysis process was 41% pyrolytic oil, 38% carbon black, 12% gas, and 8.9% steel scrap, with a calorific value of 36 MJ/kg per tire. The carbon black was composed of 90% carbon, and the pyrolytic oil was composed of 66% gasoline and 33% other oils, which have higher quality and can be commercialized with a potential profit over 3 million dollars/year.
The widespread use of plastic goods creates huge disposal issues and environmental concerns. Increasing emphasis has been paid to the notion of a circular economy, which might have a significant impact on the demand for plastic raw materials. Post-consumer plastics recycling is a major focus of the nation’s circular economy. This study focuses on energy recovery from waste plastics as an alternative fuel source to meet the circular economy demand. Waste plastic fuel produced through pyrolysis has been claimed to be utilized as a substituted fuel. This work focuses to determine the performance and emission standards of Waste Plastic Fuel (WPF) generated from the pyrolysis of High-Density Polyethylene (HDPE) in a single-cylinder Direct Injection Diesel Engine (DIDE). Three different ratios of WPF were combined with 10% ethanol and 10% ethoxy ethyl acetate as an oxygenated additive to create quaternary fuel blends. The ethanol has a low viscosity, a high oxygen content, a high hydrogen-to-carbon ratio as favourable properties, the quaternary fuel results the improved brake thermal efficiency, fuel consumption and reduced emissions. The blend WEE20 exhibits 4.7% higher brake thermal efficiency, and 7.8% reduced fuel consumption compared to the diesel. The quaternary fuel blends demonstrated decreased carbon monoxide of 3.7 to 13.4% and reduced hydrocarbons of 2 to 16% under different load conditions.
This work aims to use wax to modify a binder employed in the paving industry. This wax can be obtained either directly or as a by-product from plastic waste′s thermal cracking (pyrolysis). The study characterizes this sustainable material and the binders resulting from blending it with conventional or modified bitumen with other additives applied in the manufacture of bituminous mixtures. Different tests were used: thermogravimetric and spectroscopic analysis; consistency tests; testing of dynamic viscosity at various temperatures; and assessment of the rheologic properties of binders. As a result, several crucial findings were reached: this sustainable wax promotes changes in the viscosity of the binders, their handling temperatures can be reduced, and it contributes to some goals of the U.N. 2030 Agenda. In summary, this work allowed us to conclude that the positive effects of a suitable modification of the bituminous binders, which incorporated this wax and other additives, led to improved consistency and rheological behaviour, having provided, for example, lower temperature susceptibility and higher permanent deformation resistance.
The article analyzes the thermal degradation in the inert and oxidative atmosphere of waste vinyl panels, the main component of which is PVC. Both pyrolysis and incineration of plastic waste are difficult, complex and multifaceted processes due to several physical and chemical phenomena occurring during their performance. The coupled TG-MS (thermogravimetry-mass spectrometry) analysis combined with the Fourier transform infrared spectrometry (TG-FTIR) analysis was used to identify the decomposition mechanisms of waste vinyl panels. Thermogravimetric tests were carried out for two heating rates of 5 and 20 K/min in the temperature range of 40–1000 °C, mass losses were determined, and products resulting from thermal degradation were identified. It was found that the individual components decompose at different temperatures depending on the heating rate and the choice of an inert or oxidative atmosphere. Vinyl floor panels were treated in terms of secondary raw material, which, in the light of the circular economy, may constitute a potential energy or chemical resource.
Poland’s management of municipal waste, which amounts to over 13 million tons/year, is not efficient—about 60% of the waste is subjected to recovery processes, about 20% of all municipal waste is converted into energy, and almost 40% is landfilled. The authors of this article recognize the potential of pyrolysis as a method of the thermal processing of waste allowing the potential of the energy contained in the waste to be utilized. Pyrolysis is an economically attractive alternative to incineration, with a significantly lower environmental impact, allowing efficient waste management and the use of pyrolysis by-products in the energy sector (pyrolysis gas), or in the building materials sector (biochar). Despite so many advantages, this method is not employed in Poland. The aim of the paper is to indicate a recommended strategy for the application of pyrolysis in Poland as a method of the thermal processing of municipal solid waste. SWOT (strengths, weaknesses, opportunities, threats) analysis was used as a research method. In the first step, on the basis of the literature review, the factors which may affect the use of pyrolysis in Poland were identified. In the second step, five experts evaluated the weights of those factors and the interactions between them. The products of the weights and interactions allowed, in accordance with SWOT analysis methodology, the most desirable strategy of pyrolysis application in Poland to be determined, which turned out to be an aggressive one. This means that pyrolysis as a thermal waste processing method should be implemented on a large scale in Poland to improve the indicators of municipal waste management.
In this study, our aim was to explore the potential energy savings obtainable from the recycling of 1 tonne of Construction and Demolition Waste (C&DW) generated in the Metropolitan City of Naples. The main fraction composing the functional unit are mixed C&DW, soil and stones, concrete, iron, steel and aluminium. The results evidence that the recycling option for the C&DW is better than landfilling as well as that the production of recycled aggregates is environmentally sustainable since the induced energy and environmental impacts are lower than the avoided energy and environmental impacts in the life cycle of recycled aggregates. This LCA study shows that the transition to the Circular Economy offers many opportunities for improving the energy and environmental performances of the construction sector in the life cycle of construction materials by means of internal recycling strategies (recycling C&DW into recycled aggregates, recycled steel, iron and aluminum) as well as external recycling by using input of other sectors (agri-food by-products) for the manufacturing of construction materials. In this way, the C&D sector also contributes to realizing the energy and bioeconomy transition by disentangling itself from fossil fuel dependence.
The disposal and use of natural algae have recently been the subject of great interest, due to increasing concern for environmental protection and resource utilization. In this paper, a mini review of recent research on the pyrolysis of natural algae, especially the algae from water blooms, is presented. The chemical compositions of the natural algae are summarized, and the pyrolysis properties of different compositions are reviewed. Non-catalytic, catalytic, and integrated catalytic processes are reviewed. Different ideas and methods for the production of bio-fuel or chemicals are discussed. Apparently, deoxygenation and denitrogenation are highly necessary for algae-based bio-fuel and catalysts play an important role in these processes. In addition, the integrated catalytic process, which involves catalysis and other operation conditions aside from the thermal treatment under inert atmosphere, shows potential for the valorization of algae-based bio-oil. Based on the recent concept and progress, the research gaps are discussed, followed by the challenges and proposals to achieve high-value utilization of the natural algae.
A lifecycle model was established to explore the efficiency, economy, and greenhouse gas emissions of a non-phase-transition drying pyrolysis and mass conversion technology, based on the principle of lifecycle assessment. The evaluation scope included straw collection and transportation, drying and crushing, biomass pyrolysis, charcoal processing, and waste heat utilization. The results show that the energy output/input ratio for non-phase-transition drying pyrolysis was 20.43, and the energy efficiency was high. The pure profit from treating wet straw was USD 45.32 per ton, the profit margin of sales was 52.11%, and the economic benefit was high. The equivalent emission of CO2 was 34.10 g·MJ−1, demonstrating high environmental benefits. Therefore, non-phase-transition drying pyrolysis and mass conversion technology is a potential biomass utilization technology with energy, economic, and ecological benefits.
The concerns about increasing greenhouse gas emissions and climate change have mobilized the world towards using new materials and technologies to decarbonize the global economy. In line with this, the utilization of diverse forms of bioenergy is expected to expand in various economic sectors due to their potential to solve environmental concerns. More specifically, the carbon contained in bioenergy is mainly from biogenic carbon dioxide; thus, bioenergy utilization contributes much less to environmental impacts than fossil energy. Despite the renewability of bioenergy sources, their production is dependent on immense amounts of construction materials, chemicals, and, most importantly, energy resources. Since the production and use of the above items are also responsible for environmental problems and challenges, the sustainability of bioenergy product systems might also be questioned. Life cycle assessment is a powerful tool to quantify the environmental sustainability of various products, including bioenergy production. It also can identify the sources and causes of the environmental impacts of bioenergy product systems. Despite the significant advantages of life cycle assessment in assessing the environmental sustainability of bioenergy product systems, there are still limitations and disadvantages to using this method. Different assumptions, various inventory data, different methods of impact assessment, and many other sources of uncertainty may give rise to wide ranges of final results. These issues can negatively affect the accuracy and reliability of bioenergy product systems’ life cycle assessment results, leading to incorrect decisions and policies. In light of the above, this study critically discusses the pros and cons of life cycle assessment in bioenergy product systems, identifying the gaps and sources of uncertainty. Finally, frameworks and procedures to improve the applicability and validity of life cycle assessment are suggested to shed light on future research directions.
The pyrolysis of sewage sludge is an alternative method to recycle the contained nutrients, such as phosphorus, by material use of the resulting biochar. However, the ecological effects of pyrolysis are not easy to evaluate. Therefore, a life cycle assessment (LCA) was carried out to determine the environmental impact of sewage sludge pyrolysis and to compare it with the common method of sewage sludge incineration. In order to identify the most sustainable applications of the resulting biochar, four different scenarios were analyzed. The modeled life cycles include dewatering, drying and pyrolysis of digested sewage sludge and utilization paths of the by-products as well as various applications of the produced biochar and associated transports. The life cycle impact assessment was carried out using the ReCiPe midpoint method. The best scenario in terms of global warming potential (GWP) was the use of biochar in horticulture with net emissions of 2 g CO 2 eq./kg sewage sludge. This scenario of biochar utilization can achieve savings of 78% of CO 2 eq. emissions compared to the benchmark process of sewage sludge mono-incineration. In addition, no ecological hotspots in critical categories such as eutrophication or ecotoxicity were identified for the material use of biochar compared to the benchmark. Pyrolysis of digested sewage sludge with appropriate biochar utilization can therefore be an environmentally friendly option for both sequestering carbon and closing the nutrient cycle.
The article presents the possibilities of effective management of lignocellulosic waste by including it in the circular economy. The pyrolysis process was chosen as the thermal conversion method. This approach, due to a high flexibility of the obtained products, better quality of the solid residue (char), and the lower emission of pollutants into the atmosphere, e.g., SO2 and NOx, is a competitive solution compared to combustion process. Wood waste from alder and pine were analyzed. As part of laboratory tests, the elementary composition was determined, i.e., C, H, N, S, and O. The pyrolysis process was carried out at a temperature of 600 °C on an experimental stand for the conversion of solid fuels in a stationary bed. For the obtained data, using the Ansys Chemkin-Pro calculation tool, the detailed chemical composition of gaseous products of the pyrolysis process was modeled for a varying temperature range and residence time in the reactor. The studies have shown that for certain process conditions it is possible to obtain a high calorific value of pyrolytic gas, up to 25 MJ/m3.
Fast pyrolysis of waste from agroindustry may be an alternative choice for sustainable use of enhanced biofuels. Plastics are one option for improving the hydrogen to carbon efficiency ratio (H/Ceff) of biomass feedstock. Waste from agroindustry in blends with biomass could modify the reaction mechanism for removing oxygen by substituting decarbonylation and decarboxylation with dehydration. Firstly, fast pyrolysis was performed to find the optimal mass blending ratio for olive pomace (OP) and agroindustrial polymers (polyethylene (PE), polystyrenes (PS) and polyvinyl chloride (PVC)) according to hydrocarbon production. Experimental results for the 1.5:1 OP/PE, 1:1.5 OP/PS and 1:1.5 OP/PVC mass blending ratios at 500 °C, showed synergistic enhancement of hydrocarbon yields. Alkenes yield were enhanced for 1.5:1 OP/PE, where the light hydrocarbons fraction (C6-C10) first increased and then decreased with temperature, reaching a maximum at 650 °C. For 1:1.5 OP/PS and 1:1.5 OP/PVC, it was improved the aromatic compounds formation, being 500 °C and 650 °C the optimal reaction temperature for the former and the later, respectively. Benzene, toluene and xylene were in large quantities obtained for PS and PVC blends with OP. Additionally, the synergistic effect on pyrolysis of the blends did not show any clear trend for pyrolytic gas emissions. In general, as reaction temperature increased, CO and CO2 emissions fell and CH4 was enhanced. Finally, olefin and aromatic yields were promoted for blends with a higher H/Ceff.
The catalytic effect of mineral components (K, Ca, Mg and Na), after pre‐treatment by water leaching and adding NaCl, was evaluated in fast pyrolysis with the biomass of four types of agricultural waste (olive pomace, nutshell, almond shell, and pistachio shell). Water leaching proved to be effective at reducing mineral content in the raw materials, especially in terms of removing K. As a consequence, there was lower decarboxylation activity during fast pyrolysis, and a lower yield of phenolic compounds was obtained. The effect of adding NaCl was evaluated by varying its ratio in the blend (1, 3 and 5 wt%) and it promoted cracking and dehydration reactions, favoring the formation of light molecular‐weight compounds as carboxylic acids. © 2021 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley & Sons Ltd.
Industrial, medical, and electronic residual wastes can potentially be an important source of energy with the use of waste-to-energy (WtE) conversion technology. In Metropolitan Manila, Philippines, about 144,000 kg/d of residual wastes were being generated by the hospitals, industrial sectors, and electronic companies. Hence, imploring high potential benefits can be achieved through utilizing these wastes as feedstock for any WtE conversion facility. A technical and financial costing was performed to evaluate the feasibility of putting up a conventional pyrolysis system in Metropolitan Manila. Various modular-type scenarios of a pyrolysis system in the WtE facility were identified based on the geographical attributes of the sectoral residual wastes generators. Results showed that a 10 tons/d pyrolysis plant facility, with Brayton power set-up, can eventually produce 800 kW and generate an annual net income of PHP 83.63 M after a 2-yr breakeven period. In addition, this facility can accommodate at most 11 tons/d of residual wastes for processing. In contrast, a smaller footprint of pyrolysis-Brayton set-up consisting of three tons per day, with 1,000 kg of daily wastes and a power generation of 65 kW, can potentially produce a net income of PHP 18.06 M following a 3-yr breakeven period. The WtE business models of putting up conventional pyrolysis facilities, by presenting both the maximum and minimum scenarios in terms of plant capacity and income when intended for operation and adoption, were computed to be feasible. © 2022, Department of Science and Technology. All rights reserved.
Although biodegradable straws are widely used, they are often unsuitable for disposal in open environments and cannot be recycled in the same manner as conventional plastic straws. Hence, an effective disposal method needs to be developed. Herein, the thermochemical conversion of biodegradable straws made mostly of polylactic acid (PLA) was considered, and the effects of CO2 on the characteristics of thermochemical products produced from biodegradable straws were explored. The thermochemical conversion of the biodegradable straw in CO2 atmosphere yielded more non-condensable gases than the thermochemical conversion in N2 owing to an enhanced thermal cracking of volatiles at 800 °C. At temperatures > 600 °C in CO2, the reverse water-gas shift reaction considerably increased the CO selectivity. Using CO2 in the thermochemical conversion decreased yields of char and wax, which was attributed to CO2 enhancing thermal cracking of volatiles evolved during the thermochemical conversion and C–H and O–H bonds present in the feedstock. The CO2 thermal agent promoted the cleavage of the polymeric bond of PLA to produce up to 14-fold more lactic acid (the monomer of PLA) than that produced with N2 agent, while it suppressed radical reactions to produce fewer phenyls and polycyclic aromatic hydrocarbons. Thermochemical treatment in a CO2 environment has a significant feature of upcycling biodegradable plastic waste, such as biodegradable straws.
A lot of fishing nets have been abandoned, lost, or discarded at sea. Herein, we aimed at applying seashell waste-derived catalytic materials to a thermocatalytic process to recover a valuable commodity chemical (e.g., caprolactam) from fishing net waste (FNW) made of polyamide 6. For catalyst synthesis, seashell waste was carbonized in N2 and CO2 environments (denoted as SSWC-N2 and SSWC-CO2, respectively); here, the basicity of SSWC-CO2 was two-fold more than that of SSWC-N2. The thermocatalytic conversion of FNW was also conducted under N2 and CO2 atmospheres. Using SSWC-CO2 in the thermocatalytic conversion conducted under a CO2 atmosphere maximized the caprolactam recovery (80 wt% of FNW feedstock, the highest yield reported to date) possibly because the base-catalyzed decomposition of polyamide 6 was enhanced by more reactive cleavage of the amide linkage in CO2. SSWC-CO2 was reused for at least three cycles. In conclusion, SSWC-CO2 is a promising alternative catalyst to recover caprolactam from FNW. The findings from this study offer insights into developing a new thermocatalytic upcycling process for marine waste such as FNW and seashell waste. This aids in reducing microplastic pollution and increasing economic potential for marine waste valorization.
Organic waste, such as cattle manure, is a serious matter of concern because of its disruptive impact on the environment. Even though disposal and reclaim of cattle manure represent the first lines of intervention to solve this problem, upcycling strategies should eventually be essential to reconvert huge amounts of the waste. In the present study, a pyrolysis process was used to reclaim value from cattle manure. Through the process, cattle manure was transformed into pyrolytic gas, pyrolytic liquid, and porous carbon material. The porous carbon material was further carbonized followed by an activation step to make a supercapacitor electrode. The electrode of a hierarchical porous carbon (termed as CMPC) is formed via carbonization and activation processes of solid residue derived from the pyrolysis of cattle manure. The bicontinuous structure of CMPC provide good ion and electron transport pathways, enabling fast charge-discharge. Specifically, in a basic solution electrolyte, CMPC electrode exhibits significant specific capacitance of 161 F g⁻¹ at 0.4 A g⁻¹, comparable to or even larger than other biomass-derived carbon electrodes, and high rate-performance (62% of low-capacitance). It also shows long cycle lives for at least 10,000 charge-discharge cycles at a constant current of 2.7 A g⁻¹. As the pyrolytic gas and pyrolytic liquid had higher heating values of 7.6 MJ kg⁻¹ and 8 MJ kg⁻¹, respectively, they can potentially be used as fuels to supply heat and energy to the pyrolysis process. The cattle manure upcycling process could greatly contribute to the reduction in greenhouse gas emissions.
The conversion of forest residues into biofuels will enhance the decarbonization of the transportation sector and help the world reach its net-zero targets. Microwave-assisted catalytic pyrolysis (MACP) is an emerging thermo-catalytic conversion technology which, when coupled with low-carbon electricity, will result in negative emissions. The work described here assessed the economic feasibility and environmental impact of a novel MACP system for co-production of upgraded biofuel and high-quality biochar from forest residues. The cradle-to-gate (CTG) carbon intensity of MACP biofuel ranged from −57.3 to 27.4 g CO2-eq/MJ respectively when using either low-carbon electricity or carbon-intense electricity. Compared to petroleum fuels, a 43% to 162% reduction of GHG emissions could be achieved depending on electricity mix and methods to treat biochar co-product. The use of electricity to produce MACP biofuel as compared to directly charge electric vehicles was justified as a preferred use based on the finding that the advanced utilization of waste biomass via MACP could contribute significantly to GHG reduction of transportation fuel without sacrificing the travel distance of vehicles. The minimum selling price (MSP) of MACP biofuel was 0.53/L or increased to $1.32/L depending on the co-product revenue from biochar’s higher or lower-value applications. MACP biofuel could also be priced competitively with petroleum fuels by as early as 2026 under the planned carbon tax schedule in Canada. This co-production of upgraded biofuel and value-added biochar could bring flexibility to the biorefinery to seek the highest possible economic and environmental benefits facing the changing market and policy.
Polycyclic aromatic hydrocarbons (PAHs) formation from the pyrolysis of waste tires is inevitable because of the complexity of tire formulations and the addition of certain chemicals. In this study, the formation behavior and distribution of PAHs in three-phases were investigated from waste tires under pyrolysis conditions. The influencing factors including the temperature, heating rate, holding time, particle size, catalyzer, and atmosphere, were systematically evaluated. The results showed that PAHs were mainly concentrated in pyrolysis oil (94.59–99.03%), followed by the gas phase (0.96–5.34%), and their content was very low in the solid phase (0.01–0.99%). A higher temperature and slower heating rate lead to partial PAHs decomposition, thus reducing their emissions. The overall formation of PAHs can be inhibited when pyrolyzing coarse-grained tire powder. Furthermore, the PAHs formation mechanisms in waste tires were determined through reaction molecular dynamics, electron paramagnetic resonance, and intermediate products. Tires were mainly decomposed into benzene series, *C2H3, and *CH3; therefore, it was determined that PAHs were formed by the joint action of the hydrogen abstraction, and vinyl radical addition and methyl addition cyclization mechanisms. Among them, low and middle-ring PAHs were formed more easily, particularly naphthalene. The generation of PAHs can be inhibited by reducing the concentration of hydrocarbons and monocyclic benzene series. Regarding the distribution law and generation pathways of PAHs, our results provide guidance for reducing PAHs formation and emissions.
This study aimed to determine the feasibility of pyrolysis scenarios as sewage sludge treatment processes through cradle-to-gate life-cycle assessment and additional energy consumption, carbon emission, and economic benefit analyses, considering circular economy principles. The examined pyrolysis scenarios include slow pyrolysis with various residence times to produce activated carbon (AC) or biochar and fast pyrolysis to produce bio-oil, all with internal gas energy recovery. The functional unit (FU) in this study comprises 1000 kg of dried sludge entering the pyrolysis reactor. The overall evaluation and new product application routes address gaps in current studies on sludge treatment via pyrolysis. Environmentally, the bio-oil (-0.31 kg CO2-eq/kg FU) and biochar (-0.05 kg CO2-eq/kg FU) scenarios show considerable improvement over contemporary pyrolysis and other conventional sludge treatment methods. The AC scenarios have higher toxicity but lower carbon emissions (1.50–1.70 kg CO2-eq/kg FU) than contemporary AC production processes. Chemical reagent usage has significant effects on the environmental burden of AC production processes. The biochar and bio-oil pyrolysis scenarios achieve net energy recovery through product applications. Although the AC scenarios still require energy input, this demand can be significantly reduced by optimising moisture removal processes. Operating cost analysis indicates that the examined pyrolysis scenarios are potentially profitable. Primary product yield and market value are significant factors determining the net profit of these pyrolysis scenarios, but further assessment of capital costs is required. This study shows that bio-oil and biochar pyrolysis are eco-friendly sewage sludge treatment methods.
A life cycle assessment was performed to compare the sustainability of gasification and fast pyrolysis processes for producing bio-oil using agricultural wastes from biomass. The objective was to carry out the environmental analysis associated with the production of 1 MJ bio-oil using different agricultural wastes biomasses for both thermochemical processes to determine which process is more respectful with the environment. The life cycle assessment revealed that gasification was more detrimental to the environment for all agricultural biomasses under study. In addition, greenhouse gas emissions over a 100-year time horizon were calculated, thereby demonstrating that CO2 yield emissions were higher than those for CH4 and N2O in both thermochemical processes. Furthermore, to gain a comprehensive overview, both thermochemical processes were divided into different equipment blocks to evaluate their individual impacts. Almond shell, pistachio shell and olive stone were identified as the biomasses for which minor amount of feed was needed to produce 1 MJ bio-oil. This assessment determined that the gasification stage of the gasification process and the separation stage for fast pyrolysis, were the main contributors to all mid-point impact categories. Finally, fast pyrolysis was the most environmentally friendly option for producing 1 MJ bio-oil.
Organic waste biomass is transformed to biogas via anaerobic digestion. Biogas is typically used as a gaseous fuel to produce heat and power, incentivized by regulatory support schemes in different regions and countries. However, energy production via biogas combustion is limited to local sites, and a lower fuel quality of biogas than natural gas is another limitation on the direct use of biogas as a fuel. Alternative ways are to employ biogas as (1) pyrolysis medium to effectively modify the quality and quantity of pyrolytic products and (2) feedstock for the production of high-value commodity chemicals. In this regard, this review is aimed at providing an overview on the use of biogas either as pyrolysis medium or as renewable chemical feedstock.
Pyrolysis of the middle layer of a surgical mask (MLM) and inner and outer layers of a surgical mask (IOM) was performed to assess their potential valorization as waste-to-energy feedstocks, and the characteristics of the resulting products were investigated. Pyrolysis of the main organics in waste surgical masks occurred at a very narrow temperature range of 456–466 °C. The main product was carbon-rich and oxygen-deficient liquid oil with a high heating value (HHV) of 43.5 MJ/kg. From the life-cycle perspective, environmental benefits and advantages of this upcycling approach were verified compared with conventional waste management approaches. This study advocated the potential application of waste surgical masks as feedstocks for fuels and energy, which is beneficial to mitigate plastic pollution and achieve sustainable plastic waste-to-energy upcycling, simultaneously.
Many facets of our civilization's contemporary life are related to the use of electrical and electronic equipment (EEE). EEE replacement is becoming more common as the need for high-performance EEE grows and technical advancement accelerates. As a result, a massive quantity of electronic waste (e-waste) is generated. One way of recycling e-waste is through pyrolysis, which is a thermochemical method used to recover polymers and concentrate metals into a solid residue. Additionally, this technique may be modified or integrated with other technologies to reduce the number of organic halides produced by harmful brominated flame retardants (BFRs), often used as additives in these materials. This article provides a comprehensive review in the context of pyrolysis of e-waste and its sustainability. The structure and components of the five significant types of e-waste, including printed circuit boards (PCBs), lithium-ion batteries (LIBs), tantalum capacitors (TCs), light-emitting diodes (LEDs), and liquid crystal displays (LCDs), are first discussed. Then five methods of e-waste pyrolysis, including vacuum pyrolysis, catalytic pyrolysis, co-pyrolysis, microwave pyrolysis, and plasma pyrolysis, have been carefully studied and the merits and demerits of each method are presented. In the following, the sustainability of the pyrolysis process is examined from three perspectives: economic, environmental, and social. In the end, ongoing challenges of e-waste pyrolysis and recommendations for future directions are also addressed. E-waste pyrolysis is still not completely industrialized. However, it can be said that it is a sustainable method, and the suitability of this method has been proven on the laboratory scale. It is hoped that we will see the industrialization of this method in industrialized and developing countries in the future.
Everyday waste is a serious matter of concern because of its disruptive impact on the environment. Although disposal and reclaim of such material represent the first lines of intervention to solve this problem, upcycling strategies should eventually be necessary to reconvert huge amounts of the waste. In addition to waste, climate change caused by greenhouse gas emissions (e.g., carbon dioxide (CO2)) is other global environmental problem. Here, we employed a thermal treatment process conducted in CO2 environment to upcycle waste tea bag (a surrogate feedstock for everyday waste) and utilize CO2 simultaneously. Through lab-scale experiments, 6 wt% caprolactam (a value-added nylon monomer), 12.7 wt% combustible gases (higher heating value (HHV): 24.8 MJ kg⁻¹), and 13.8 wt% char (HHV: 28.1 MJ kg⁻¹) were obtained at 500 °C. Based on the experimental results, a large-scale energy analysis of the process was conducted by developing a simulation model of an integrated process to produce caprolactam-rich liquid product. For the integrated process, CO2 in gaseous product mixture is separated, and the separated CO2 is recirculated to the thermal treatment step. The combustible gases and char are used to supply energy to thermal treatment and separation steps. The proposed process has a significant feature that there is no need for external energy with no CO2 emission (i.e., CO2 is fully recirculated in the waste treatment process).
Climate change mitigation not only requires reductions of greenhouse gas emissions, but also withdrawal of carbon dioxide (CO2) from the atmosphere. Here we review the relationship between emissions reductions and CO2 removal by biochar systems, which are based on pyrolysing biomass to produce biochar, used for soil application, and renewable bioenergy. Half of the emission reductions and the majority of CO2 removal result from the one to two orders of magnitude longer persistence of biochar than the biomass it is made from. Globally, biochar systems could deliver emission reductions of 3.4–6.3 PgCO2e, half of which constitutes CO2 removal. Relevant trade-offs exist between making and sequestering biochar in soil or producing more energy. Importantly, these trade-offs depend on what type of energy is replaced: relative to producing bioenergy, emissions of biochar systems increase by 3% when biochar replaces coal, whereas emissions decrease by 95% when biochar replaces renewable energy. The lack of a clear relationship between crop yield increases in response to fertilizer and to biochar additions suggests opportunities for biochar to increase crop yields where fertilizer alone is not effective, but also questions blanket recommendations based on known fertilizer responses. Locally specific decision support must recognize these relationships and trade-offs to establish carbon-trading mechanisms that facilitate a judicious implementation commensurate with climate change mitigation needs.
The effectiveness of a recycling approach of the printed circuit board (PCBs), and, thus, the quality of polymeric constituents, primarily rests on the capacity to eliminate the bromine content (mainly as HBr). HBr is emitted in appreciable quantities during thermal decomposition of PCB-contained brominated flame retardants (BFRs). The highly corrosive, yet relatively reactive HBr, renders recovery of bromine-free hydrocarbons streams from brominated polymers in PCBs very challenging. Via combined experimental and theoretical frameworks, this study explores the potential of deploying alumina (Al2O3) as a debromination agent of Br-containing hydrocarbon fractions in PCBs. A consensus from a wide array of characterization techniques utilized herein (ICP-OES, IC, XRD, FTIR, SEM-EDX, and TGA) clearly demonstrates the transformation of alumina upon its co-pyrolysis with the non-metallic fractions of PCBs, into aluminum bromides and oxy-bromides. ICP-OES measurements disclose the presence of high concentration of Cu in the non-metallic fraction of PCB, along with minor levels of selected valuable metals. Likewise, elemental ionic analysis by IC demonstrates an elevated concentration of bromine in washed alumina-PCBs pyrolysates, especially at 500 °C. The Coats-Redfern model facilitates the derivation of thermo-kinetic parameters underpinning the thermal degradation of alumina-PCB mixtures. Density functional theory calculations (DFT) establish an accessible reaction pathway for the HBr uptake by the alumina surface, thus elucidating chemical reactions governing the observed alumina debromination activity. Findings from this study illustrate the capacity of alumina as a HBr fixation agent during the thermal treatment of e-waste.
To promote the use of recycled waste materials as an industrial feedstock, this study examined the preparation of carbon black (CB) by partial oxidation of a spent tyre pyrolysis oil using a drop tube furnace. The effect of reaction temperature, the residence time of gas in the reactor and inlet gas oxygen concentration on the yield and properties of the CB were evaluated. The surface chemistry, chemical composition, morphological and thermal properties of the CB samples were characterised using XPS, EA, TEM, BET, and TGA, respectively. The CB yield increased with increasing reaction temperature but decreased as the residence time or oxygen concentration increases. The CB primarily consisted of C (90.5–98.6%) and O (0.9–7.4%), with small traces of S (<1%), Si (<1%) and H (<2%). Hydroxyl, carbonyl, and carboxyl are the key functional groups found on the CB surface, with the hydroxyl groups being dominant. The CB were highly graphitic with a lattice spacing in the range of 0.338–0.350 nm and had BET surface areas of 4–22 m²g⁻¹. The mean primary particle size ranged from 92 to 176 nm and decreased with increasing reaction temperature and oxygen concentration. The CB aggregate configuration became more complex with increasing reaction temperature, residence time and oxygen concentration. The results were not only comparable with commercial CB products from fossil fuel feedstocks but are expected to provide the needed motivation to move towards circular economy strategies, which have positive impacts from a sustainability perspective.
A novel method for preparing porous carbon materials from biomass pyrolysis vapors with calcium citrate template has been proposed. The effects of pyrolysis temperature, pyrolysis heating rate and carbon-containing precursor preparation temperature on the yield of biomass pyrolysis products, composition of light bio-oil and structure of porous carbons were investigated. The physicochemical characterization and hydrogen adsorption experiments were carried out for the prepared porous carbons. The carbonization mechanism of the carbon-containing precursor was studied and a five-stage reaction kinetic model was established by Gaussian peak separation method according to the DTG curves. Under the optimal conditions of pyrolysis temperature (823 K), heating rate (10 K/min) and carbon-containing precursor preparation temperature (473 K), the prepared porous carbon material has the largest specific surface area of 1703 m²/g, relatively high micropore volume of 0.51 cm³/g and microporosity of 24.17%. The hydrogen adsorption capacity of the carbon material can reach 170.12 cm³/g (1.53 wt%) at 77 K at atmospheric pressure. This paper provides a novel and environmental-friendly method for the preparation of porous carbon materials, and also presents a new way for the utilization of biomass pyrolysis vapors before condensation.
The continuous growth of population and the steady improvement of people's living standards have accelerated the generation of massive food waste. Untreated food waste has great potential to harm the environment and human health due to bad odor release, bacterial leaching, and virus transmission. However, the application of traditional disposal techniques like composting, landfilling, animal feeding, and anaerobic digestion are difficult to ease the environmental burdens because of problems such as large land occupation, virus transmission, hazardous gas emissions, and poor efficiency. Pyrolysis is a practical and promising route to reduce the environmental burden by converting food waste into bioenergy. This paper aims to analyze the characteristics of food waste, introduce the production of biofuels from conventional and advanced pyrolysis of food waste, and provide a basis for scientific disposal and sustainable management of food waste. The review shows that co-pyrolysis and catalytic pyrolysis significantly impact the pyrolysis process and product characteristics. The addition of tire waste promotes the synthesis of hydrocarbons and inhibits the formation of oxygenated compounds efficiently. The application of calcium oxide (CaO) exhibits good performance in the increment of bio-oil yield and hydrocarbon content. Based on this literature review, pyrolysis can be considered as the optimal technique for dealing with food waste and producing valuable products.
Lignocellulosic biomass is an effective and sustainable alternative for petroleum-derived fuels and chemicals to produce biofuels and bio-based products. Despite the high availability, the degradation of biomass is a substantial challenge. Hence, it is necessary to integrate several unit processes such as biochemical, thermochemical, physical, and catalytic conversion technologies to produce a wide range of bio-based products. Integrating the processes enhances the yield, reduces the reaction time, and can be cost-effective. Process integration could significantly lead to various outcomes which guide towards the circular economy. This review addresses integration of several biorefinery processes for the production of multifaceted products. In addition, modern and sustainable biorefinery technologies are discussed to pave the path towards circular economy through the closed-loop approach.
In the interest of utilisation of industrial waste products, this paper investigated the preparation and characterisation of carbon black (CB) made via partial oxidation of a heavy residue fraction (HRF) of spent tyre pyrolysis oil in a drop tube furnace. The effect of process temperature, residence time (Rtime), and O2 concentration on the yield and quality (elemental composition, functional groups, morphology, thermal behaviour, and surface area) of HRF-CB were determined using elemental analyser (EA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analyser (TGA), and Brunauer-Emmett-Teller (BET) technique. Higher temperatures led to higher yields (41 – 60%) and better quality of the resultant CB. Above 1150°C, the CB samples were comparable with commercial CB products, with low ash (<0.1%), low volatile matter (<6.1%), moderate BET surface area (11 – 24.2 m²g⁻¹), and high C contents (~94 – 99%). Quality was also improved as Rtime or O2 increased but at some sacrifice to the total yield. HRF-CB aggregates were morphologically complex, highly structured and had good thermal stability, which increased with increasing process temperature, Rtime and O2 concentration, respectively. Interestingly, the hydroxyl, carbonyl and carboxyl surface groups in the HRF-CB were higher (54 – 69%) than commercial products (0 – 59%) under all process conditions, which is a desirable trait for enhanced bonding and mechanical properties but typically introduced to commercial CB by secondary procedures. Given their comparable properties, CB from heavy residues of spent tyre pyrolysis oil may be a suitable replacement for commercial CBs used in rubber reinforcement.
The EU is experiencing economic growth that exceeds domestic raw material/energy production. The EC is trying to solve this problem of the unsustainability of its economic development through two separate legislative frameworks—one trying to solve material supply problems, and one for solving problems of energy dependence. This division is also present in waste-related legislation where emphasis is put on “closing the loop” on the material side through material recovery. In this chapter, a “closing two loops” approach is defined, which builds upon material recovery-based approach to waste management and boosts its sustainability by at the same time closing the loop from two sides—material and energy. The significance of energy recovery is demonstrated through the use of cumulative energy demand-based indices, combined with LCA-based system modeling, for comparison of different scenarios that use material and energy recovery to a different extent and, at the same time, meet all current legislative goals.
