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Plastics are abundant and have a high energy content making their use in energy applications attractive. This article presents a review on plastic waste (PW) management by pyrolysis and gasification, which are two types of thermochemical conversion (TCC) techniques. The conversion of PW and the application of its converted products are important steps toward reducing reliance on fossil fuels, enhancing closed-loop recycling of materials and the circular economy. The review presented herein also focuses on product distribution and yields with emphasis on the energy content and potential integration to energy systems and grids. It is found that pyro-oils have properties similar to conventional fuels such as diesel and can partially substitute for fossil fuels. In fact, the energy content of PW pyro-oils obtained by various researchers range from 41.10−46.16 MJ kg−1 , which is close to the heating values of conventional fuels and thus are potential candidates for fuel applications. Typical treatment post-conversion is also conducted to maintain the quality of the oil produced and the removal of sulfur content to conform with market standards. On the other hand, syngas produced during gasification possesses a lower potential for fuel applications as its energy content may reach values as low as 20 MJ kg−1 in comparison to pyro-oil. However, depending on the process conditions, it is possible to increase the energy content to values of over 40 MJ kg−1 . Additionally, syngas is the building block for many valuable chemicals. With appropriate treatment, the syngas obtained from the gasification of PW can be used in gas engines and can be converted to commercial products such as liquid fuels via the Fischer−Tropsch synthesis. This review also highlights some available commercial-scale plants for the TCC of PW and real-life application of their obtained products. It is noted that the integration of the processes to energy systems is technically and economically feasible. Real-life applications of products obtained from the pyrolysis and gasification of PW in different parts of the world are also discussed. The produced fuels have been used in cooking stoves and burned in a gas turbine, internal combustion engine, and direct injection diesel engine.

With fossil fuel being the major source of energy, CO2 emission levels need to be reduced to a minimal amount namely from anthropogenic sources. Energy consumption is expected to rise by 48% in the next 30 years, and global warming is becoming an alarming issue which needs to be addressed on a thorough technical basis. Nonetheless, exploring CO2 capture using membrane contactor technology has shown great potential to be applied and utilised by industry to deal with post- and pre-combustion of CO2. A systematic review of the literature has been conducted to analyse and assess CO2 removal using membrane contactors for capturing techniques in industrial processes. The review began with a total of 2650 papers, which were obtained from three major databases, and then were excluded down to a final number of 525 papers following a defined set of criteria. The results showed that the use of hollow fibre membranes have demonstrated popularity, as well as the use of amine solvents for CO2 removal. This current systematic review in CO2 removal and capture is an important milestone in the synthesis of up to date research with the potential to serve as a benchmark databank for further research in similar areas of work. This study provides the first systematic enquiry in the evidence to research further sustainable methods to capture and separate CO2.

End of life single-use items such as carrier bags constitute a large proportion of the litter found in marine and terrestrial environments. The main objective of the current work was to investigate the response of an oxo-biodegradable commercial plastic film product to photo-degradation using accelerated weathering, verifying the claim of its biodegradability and suitability as an eco-friendly product. This study is also geared towards the appropriateness of such products to reduce plastic waste accumulation in urban environments. The film samples were exposed to weathering as a means to determine the impact of UV induced oxo-biodegradation. Haze (%), light transmission (%) and the total change in colour (ΔE) were measured as indicators to the degradation profile of the polymeric materials, in addition to tensile pull mechanical properties and thermal stability. The melting peak indicates the melting point (Tm) of the polymer and with exposure to weathering it showed a slight decrease from 105 to 102 °C indicating that biodegradation mechanisms were triggered to a certain extent. The reduction in strain at rupture was also indicative for a loss in crystalline structure, coupled with Young’s modulus increase throughout the weathering exposure tests. Therefore, the material studied could be a candidate to mitigate the accumulation of plastic waste in open environments based on the results of this study whilst regulating controlled substances.

Landfilling is Kuwait’s only waste disposal method. It presents an economical and a reliable solution in waste management but can pose a threat to human health and environment, making rehabilitation and restoration of these areas critical for future developments. Moreover, improper handling and management of waste in landfill sites could result in release of toxic gases and leachate contamination and might have a long-term impact on the environment. Thus, the objective of this study was to establish a baseline soil characterisation for the planning of landfill restoration based on the contamination of heavy metals and organic pollutants in these sites. The contamination and soil permeability of three of Kuwait’s active landfills, namely the South Seven Ring Road, Mina Abdullah, and A-Jahra, were quantified. These landfills are under consideration by the government for restoration and future developments. The granulometric distribution and waste handling for these landfills were quantified. Hydraulic conductivity (k) of the soil samples was estimated to determine the nature of the soil. A series of heavy metals and organic pollutants were also quantified in laboratory and compared to the Canadian and Australian guidelines. Though these contaminants were mostly within the level of threshold of their toxicity, the sites should be handled properly and carefully for restoration and future uses as the bioavailability may change with alterations and should be tested in future.

This article shows a preliminary study of an end of life tyres (ELTs) use as a feedstock in a newly developed and patented reactor system that utilises a three zone heating element set-up along its fixed bed. The pyrolysis reaction was conducted between 500 to 700 °C and has yielded a maximum pyrolysis oil at 500 °C which was attributed to the promotion of secondary cracking of the oil into permanent (non-condensable) gaseous products. The oil yield and properties including estimated mass balance, sulphur content and higher heating value (HHV) shows that the pyro-oil is within fuel standards of the market making it a green and renewable resource off of waste. In addition, The hydrocarbon (HC) range of the products obtained from the oil shows that it is within the diesel range of typical fuels. The analysis of the gaseous products from the pyrolysis showed that an increase in the average reactor bed temperature promotes the decomposition of primary HC and pyrolysis oil into secondary products. This results in the detection of tetradecanoic acid, limonene and eicosane, among other major chemical groups at temperatures above 550 °C which is the end-set temperature of feedstock examined. It can be concluded that by using such a reactor set-up and upgrading the fuels extracted from its downstream stigmatic features of fixed bed reactors might be overcome with a lucrative economical value and rate of return in a circular economy perspective.

A process simulation and techno-economic evaluation of using molten solar salt as the heating medium for pyrolysis of mixed plastic waste (MPW) containing poly(vinyl chloride) (PVC) was performed. ...

The present study investigates the steam gasification of biomass with an in-process CO2 capture. The work is aimed at achieving hydrogen enrichment while reducing the carbon dioxide (CO2) concentra...

A computational fluid dynamics (CFD) model was derived and validated in order to investigate the hydrodeoxygenation reaction of 4-propylguaiacol, which is a lignin-derived compound present in bio-oil. A 2-D packed bed microreactor was simulated using a pre-sulphided NiMo/Al2O3 solid catalyst in isothermal operation. A pseudo-homogeneous model was first created to validate the experimental results from the literature. Various operational parameters were investigated and validated with experimental data, such as temperature, pressure and liquid flow rate, and it was found that the CFD findings were in very good agreement with the results from the literature. The model was then upgraded to that of a detailed multiphase configuration, and phenomena such as internal and external mass transfer limitations were investigated, as well as reactant concentrations on the rate of 4-propylguaiacol. Both models were in agreement with the experimental data, and therefore confirm their ability for applications related to the prediction of the behaviour of bio-oil compound hydrodeoxygenation.

In this work, end of life tyres (ELTs) samples were subjected to pyrolysis in a dynamic thermogravimetry set-up under various heating rates between 5°C and 25°C min−1. The experimental design involved dried and non-dried sample results in an isothermal step within the heating program, to be able to compare the data against non-dried samples, to further investigate the effect of drying on the results obtained. The drying of the samples resulted in an increase in the onset temperature by some 30°C. However, cryomilling the ELTs samples showed a great effect in reducing the onset of the degradation curve by about 10°C amongst the same set of experiments. The type of sample, in terms of size and processing/milling condition, had a significant impact on the heat flow properties and calorimetry reported. The exothermic region for the original shavings resulted in an enthalpy of −48 J g−1, whilst the cutting mill samples exhibited an enthalpy increase to −184 J g−1. However, the cryomilled samples showed an enthalpy increase estimated at 139 J g−1.

The aim of this study is to assess the effect of leached pollutants from solid waste landfills on shallow utilized aquifers within the State of Kuwait. The objectives of the work were achieved through developing a 3D-VMF Flex numerical flow and solute transport model. The results of the study of Kuwait show that the pollutants longitudinal dispersivity should be less than or equal to 420 m coupled with a ratio of horizontal transverse to longitudinal dispersivity equal to 0.1 and a vertical transverse dispersivity to longitudinal dispersivity ratio equal to 0.01. The novelty of this research is that the developed model was for the first time simulating concurrently the three processes that control the movement of pollutants in the porous media under landfills in Kuwait: advection, dispersion and adsorption. The dispersion and adsorption model parameters were calibrated against measured pollutants concentration in the field. This study shows that the adsorption process plays an important role in controlling the migrantion of heavy metals and inorganic pollutions into shallow aquifers. This study calibrates adsorption coefficient (kd) for conservative pollutants such as Cl to be 1 × 10–7 (mg/l)−1, for nitrogen compound such as NO3 to be 1.2 × 10–7 (mg/l)−1 and for heavy metals such as Pb and Cr to be 1 × 10–5 (mg/l)−1. It was also concluded that conservative pollutants take about one year to leach to the closets observational point (2.57 km). It took the conservative pollutant plume about 16.5 years (6000 days) to reach the furthest observation point, which is 5.26 km away. These conclusions combined draw a priority action-plan for interested parties to take into considerations future works for land and environmental rehabilitation strategies including natural underground water resources management.

With increases in population and industrialization, global energy demand is increasing rapidly and resulting in various environmental challenges related to fossil fuel consumption. These challenges have made it imperative to look for alternative means of environmentally sustainable energy production, such as the thermal degradation of biomass. Biofuels obtained from pyrolysis have the potential to be substituted for fossil fuels, but one of the major barriers to utilization of pyrolysis oil is the presence of oxygenated compounds. An approach to overcome this is to co-pyrolyze the biomass with hydrogen-rich feedstocks such as plastic and tire wastes. Studies have shown that exists a synergistic relationship between plastics/tires and biomass as well as resulting products from co-pyrolysis have higher heating value along with improved bio-oil properties. This paper discusses the current progress on the co-pyrolysis of biomass with waste plastics/tires and their synergistic interactions for high grade fuel production. Co-pyrolysis studies done on pilot-scale have also been discussed in this review.

Pyrolysis is a promising thermolysis technique to recover valuable oils and light hydrocarbons (HC) with high yields from plastic solid waste (PSW). In this work, thermal pyrolysis of high density polyethylene (HDPE) with the aim of producing gasoline range hydrocarbon oils, has been carried out in a novel fixed bed (batch) reactor. The pyrolysis of HDPE has been conducted between 500 to 800 °C in the presence of nitrogen as an inert carrier gas media to produce liquid fuel oil, gaseous products and solid char. The optimum temperature of obtaining maximum oil product yield (70%) was 550° C. A comprehensive gas chromatography (GC) analysis of the liquid and gaseous products was conducted to quantify high molecular weight individual HC components. Moreover, light molecular weight HC constituting the gaseous fraction were identified. A chemical kinetic analysis of the cracking reactions, was performed to investigate the reaction mechanism of yielding the maximum oil product. The oil product recovered had a high proportion of aliphatic HC especially in the range of C8 to C12, whilst aromatic HC were of lower proportion. The carbon number of the pyrolysis oil was noted to increase proportionally with the increasing operating temperature. The gaseous product had a high percentage (> 70%) of C2 to C4 HC, which was attributed to the high activity of carbon/carbon (C-C) chain scission reaction.

In this study, the properties of virgin linear low-density polyethylene (LLDPE) and its blends with reclaimed plastic solid waste (PSW) are investigated by thermogravimetry, differential scanning calorimetry (DSC), infrared spectroscopy and scanning electron microscopy (SEM). The PSW constituted polyolefin (PO) polymers recycled mechanically via extrusion/blown-film and exposed to accelerated weathering tests to determine the change in their degradation behaviour. The oxidation products determined using the FTIR analysis and thermal stability studies points toward the blend constituting 25% of waste by weight as the most stable. Changes in crystallinity of the polymers were attributed to the crystal size change as a consequence of the weathering mechanism. The DSC results revealed that both oxidation induction temperature (OIT) and crystallinity were affected by the PO waste content. This points towards the impact of polymers immiscibility and polydispersity within the matrix of the blends due to chain scission reaction and oxidation with the UV exposure.

This study investigates the calcination and carbonation reaction kinetics of eggshell. Nonisothermal (dynamic) thermogravimetry using multiple heating rates was conducted to study the calcination process. On the other hand, isothermal conditions were applied to report on the carbonation process in a carbon dioxide (CO2) atmosphere. Several model-based and isoconversional kinetic methods were used to evaluate the calcination kinetic parameters. The methods include the Friedman, Coats and Redfern, modified Coats and Redfern, Kissinger, Flynn–Wall–Ozawa, and Kissinger–Akahira–Sunose methods. Furthermore, an analytical solution method was developed to evaluate the kinetic parameters and to predict the experimental conversion. The carbonation reaction was modeled with a modified form of the shrinking core model. Both the rapid surface reaction-controlled and the slow diffusion-limited stages of carbonation were analyzed. The results showed that the kinetic parameters obtained with the various methods are in go...

In this work, real life reclaimed plastic solid waste (PSW) secured from the municipal sector was mechanically recycled and compounded with virgin linear low density polyethylene (LLDPE). The compounding of the plastic film samples utilised the means of extrusion and blown filming to produce various formulations of the blends containing up to 100% (by weight) of the PSW in the examined specimens. The film samples were compared to market products used in the State of Kuwait where PSW accumulation presents a major obstacle. Natural weathering under arid and harsh climatic conditions was also performed to determine the degradation extent of the film samples. Haze (%), light transmission (%) and the total change in colour (ΔE) were measured as indicators to the degradation profile of the polymeric materials, in addition to tensile pull mechanical properties. Properties were noted to deteriorate as a function of weathering time and waste content. Statistical analysis was also performed on the properties measured and climatic conditions including airborne pollutants levels. The abundance of the secondary airborne pollutant (ozone) was determined to be a significant variable on the studied properties. This can be attributed to induced photo-oxidation the polymeric matrix is subjected to under such climatic conditions which increases oxygen diffusion throughout the polymeric matrix. Future development of the recycled blends studied in this work can be a route for the decrease of associated environmental stressors with virgin plastic resin conversion.

It is imperative to have soil guidelines that consider commodities on the market especially biodegradable plastics that are increasing in popularity nowadays. In this short communication, heavy metal in soil was investigated after degrading plastics commonly used on the market. The plastic materials included virgin linear low-density polyethylene, plastic waste of polyolefin origin, and biodegradables of oxo- and hydro-based types. Soil/water matrix that simulates arid land conditions was used. Metals including cobalt, chromium, cadmium, and nickel, among others, were studied after exposure of three continuous months. It was noted that background concentrations reduced with water indicating that leachate might contain the majority of the transferred metals from plastics. In particular, the concentration of nickel in soil was detected to be 84 ppm after exposure to type I of the oxo-biodegradable commercial plastics. Furthermore, the material of similar source started to retain nickel by day 74 of exposure. This surpasses both Canadian and Australian guidelines discussed herein. Furthermore, nickel concentrations exceeded international guidelines and point towards the need for remediation. Mean values of chromium exceeded soil control results and the USA remediation values in the case of single screw compounded plastics. It should also be noted that the work conducted points towards metal trace detection limits that are tied to waste and sludge disposal in an improper manner with time.

Polymer waste was subjected to biodegradation evaluation after compounding specimens with an oxo-prodegradant chemical (PDQ-M) and thermoplastic starch, to determine its susceptibility to degrade with time in contact with soil simulating an arid environment. The ASTM D 5988–18 test method was followed to evaluate the biodegradation extent of the materials under investigation, whilst using linear low density polyethylene (LLDPE), polycaprolactone (PCL) and TPS alongside the starch (positive control) as reference materials. The samples were also subjected to thermal characterisation using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), in addition to studying their infrared spectra (IR). It was noted that the LLPDE and the oxo-prodegradant induced polymer waste had a similar degradation extent evaluated after rigorous testing and monitoring, which was 23% after 180 days of experimental time. Furthermore, a plateau was reached for the biodegradation (%) as a function of time after some 50 days, which indicate that the additives in the samples act as a source of nutrient to sustain the biodegradation by enriching the microorganisms in the soil to produce carbon. The work in this study points towards a new method for treating polymer waste using physical blending with additives to biodegrade it with time as promising alternative for plastic waste accumulation.

Plastic production and use are currently widespread. However, plastic wastes are non-biodegradable and leave a high carbon footprint, posing challenges to ecosystems and the environment. Therefore, innovative recycling technologies should be geared towards waste-to-energy conversion solutions. Chemical recycling technologies that convert plastic wastes into feedstocks for liquid hydrocarbon fuels and chemical production are highly desirable. This chapter provides a detailed discussion of the possible plastic reuses such as for (a) hydrogen production, (b) production of gasoline and diesel fuel, (c) production of chemicals or chemical building materials, and (d) co-processing with other feedstocks. Because of the high carbon and energy content of plastics, environmentally friendly and cost-effective production of carbon nanomaterials can also be achieved by using plastic waste conversion technologies. The technical challenges and future potential of plastic waste recycling are also discussed.

The rapid growth and urbanization rate, coupled with hot climate and scarce rainfall, makes it essential for a country like Kuwait to have several power and desalination plants with high-generating capacity. These plants are entirely reliant on burning fossil fuels as a source of thermal energy. These plants are also universally accepted to be the largest CO2 emitters; hence, they present a potential for carbon capture and storage (CCS). Having established the suitability of the existing conditions for post-combustion CCS, a techno-economic-based feasibility study, which took into consideration local power generation technologies and economic conditions, was performed. Relying on fifteen case study models and utilizing the concept of levelized cost of electricity (LCOE), the statistical average method (SAM) was used to assess CCS based on realistic and reliable economic indicators. Zour power station, offering the highest potential CO2 stream, was selected as a good candidate for the analysis at hand. Heavy fuel oil (HFO) was assumed to be the only fuel type used at this station with affixed price of USD 20/barrel. The analysis shows that the internal rate of return (IRR) was about 7%, which could be attributed to fuel prices in Kuwait and governmental support, i.e., waived construction tax and subsidized workforce salaries. Furthermore, the net present value (NPV) was also estimated as USD 47,928 million with a 13-year payback period (PBP). Moreover, 1–3% reductions in the annual operational cost were reflected in increasing the IRR and the NPV to 9–11% and USD 104,085–193,945 million, respectively, and decreasing the PBP to 12–11 years. On the contrary, increasing the annual operational cost by 1% made the project economically unfeasible, while an increase of 3% resulted in negative IRR (−1%), NVP (−USD 185,458 million) and increased PBP to 30 years. Similarly, increasing the HFO barrel price by USD 5 resulted in negative IRR (−10%) and NVP (−USD 590,409); hence, a CCS project was deemed economically unfeasible. While the study considered the conditions in Kuwait, it is expected that similar results could be obtained for other countries with an oil-driven economy. Considering that around 62% of the fossil fuel blend in Kuwait is consumed by electricity and water generation, it is inevitable to consider the possibility and practicality of having a carbon network with neighboring countries where other oil-driven economies, such as Kingdom of Saudi Arabia and Iraq, can utilize a CCS-based mega infrastructure in Kuwait. The choice of Kuwait is also logical due to being a mid-point between both countries and can initiate a trading scheme in oil derivatives with both countries.

Marine plastic litter has been a major concern over the past decade particularly in semi-enclosed seas such as the Arabian/Persian Gulf, which are likely to impose a relatively higher threat to ecosystem and human health. In this work, we have focused our efforts on the transport features of marine surface microplastics (MPs) in the Gulf. The assessment utilizes a 3D hydrodynamic model of the northern Gulf which was coupled with a particle tracking model. We have considered five release locations and investigated two dominant wind conditions by applying different numerical scenarios. The results revealed that the northerly winds result in high dispersion and seaward transport of MPs in the open coastal zones, while in semi-enclosed regions they result in high trapping and beaching verified by visual investigation. The study shows that further detailed field investigations are warranted to enable the models to better parameterize the fate and distributions of MPs.

Transition metal nitrides possess superior mechanical, physical, and chemical properties that make them desirable materials for a broad range of applications. A prime example is zirconium nitride (ZrN), which can be obtained through different fabrication methods that require the applications of high temperature and pressure. The present work reports an interesting procedure for synthesizing disordered face centered cubic (fcc)-ZrN nanoparticles through the reactive ball milling (RBM) technique. One attractive point of this study is utilizing inexpensive solid-waste (SW) zirconium (Zr) rods as feedstock materials to fabricate ZrN nanopowders. The as-received SW Zr rods were chemically cleaned and activated, arc-melted, and then disintegrated into powders to obtain the starting Zr metal powders. The powders were charged and sealed under nitrogen gas using a pressurized milling steel vial. After 86 ks of milling, a single fcc-ZrN phase was obtained. This phase transformed into a metastable fcc-phase upon RBM for 259 ks. The disordered ZrN powders revealed good morphological characteristics of spherical shapes and ultrafine nanosize (3.5 nm). The synthetic ZrN nanopowders were consolidated through a spark plasma sintering (SPS) technique into nearly full-density (99.3% of the theoretical density for ZrN) pellets. SPS has proven to be an integral step in leading to desirable and controlled grain growth. Moreover, the sintered materials were not transformed into any other phase(s) upon consolidation at 1673 K. The results indicated that increasing the RBM time led to a significant decrease in the grain size of the ZrN powders. As a result, the microhardness of the consolidated samples was consequently improved with increasing RBM time.

Hydrogen, which is a new clean energy option for future energy systems possesses pioneering characteristics making it a desirable carbon-free energy carrier. Hydrogen storage plays a crucial role in initiating a hydrogen economy. Due to its low density, the storage of hydrogen in the gaseous and liquids states had several technical and economic challenges. Despite these traditional approaches, magnesium hydride (MgH2), which has high gravimetric and volumetric hydrogen density, offers an excellent potential option for utilizing hydrogen in automobiles and other electrical systems. In contrast to its attractive properties, MgH2 should be mechanically and chemically treated to reduce its high activation energy and enhance its modest hydrogen sorption/desorption kinetics. The present study aims to investigate the influence of doping mechanically-treated Mg metal with 5 wt% amorphous Zr2Cu abrasive nanopowders in improving its kinetics and cyclability behaviors. For the first time, solid-waste Mg, Zr, and Cu metals were utilized for preparing MgH2 and amorphous Zr2Cu alloy (catalytic agent), using hydrogen gas-reactive ball milling, and arc melting techniques, respectively. This new nanocomposite system revealed high-capacity hydrogen storage (6.6 wt%) with superior kinetics and extraordinary long cycle-life-time (1100 h) at 250 °C.

Microplastics are recognised as a (persistent) pollutant and are believed to be ubiquitous in the marine environment. The importance of this issue is evident from the large number of technical publications and research efforts within the past decade. However, the Arabian (Persian) Gulf region has few reported datasets in spite of being an area with excessive plastic use and a hefty generation rate of plastic solid waste. This communication aims at stimulating a discussion on this topic focusing on the available regional and international datasets, along with the environmental conditions that are likely to contribute to the disintegration and transport of the plastic debris rendering it as microplastic. This work also highlights some of the constraints in sampling techniques, identification methods, and the reported units of microplastics. Most studies employ neuston nets of variable dimensions that samples different thicknesses of surface water, which also posses a major constraint in standardising field sample collection. Extrapolation of a trawl to units such as particles.km-2 without considering the fact that neuston nets collect three-dimensional samples, is also another aspect discussed in this communication. This study also intends to initiate a discussion on standardising the practices across the region to enable an intercomparison of the reported data. In addition, it calls for a comprehensive assessment using the standardized methodology for putting a mitigation plan for microplastics as a potential threat detected in environmental sinks.

In this communication, we discuss various production methods as potential venues targeted towards alternative fuel generation. These will revolve around the Fischer–Tropsch (FT) process and biodiesel and hydrogen generation techniques. The implementation of membrane reactors in the production of fuels will be shown and discussed; and their advantages will be detailed. The main routes of hydrogen production are also detailed, which include autothermal reforming and biological process. This was done to compare the main advantages of various techniques for the production of hydrogen, as it is noted to be the most desired utility fuel that can serve various purposes. The application of membranes also facilitates an increase in the conversion of desired products while shifting the equilibrium of the reaction and reducing undesired by-products. Membrane reactors also overcome immiscibility issues that hinder conventional reactor processes. Membrane reactors are also demonstrated to reduce the difficulty in separating and purifying impurities, as they couple separation and reaction in one process. This shows drastic economic and energy requirement reductions in the amount of wastewater treatment associated with conventional fuel production reactor. Emphasis is also paid to catalytic membranes used for the production of biodiesel, which can also remove glycerol from the product line as an added advantage.

This study presents the thermo-chemical conversion by means of pyrolysis as a route to valorise end of life tyres (ELTs) in a sustainable manner whilst targeting produced pyrolysis oil (pyro-oil) to replace conventional fossil fuels. The work presented here compares the results of pyro-oil extracted from the pyrolysis of three tyre grades, namely fresh (new) tyres, car and lorry truck ELTs; and investigates the pyro-oil extracted for fuel properties and common fuel hydrocarbon range. A fixed bed reactor system was used to conduct the experimental runs between 500 and 800 °C. The results show that fresh tyres and car ELTs yield some 45% of pyro-oil at an average reactor bed temperature equal to 600 °C which promotes evolution of liquid hydrocarbons via primary route of tyres cracking, hence pyro-oil production to a maximum. Furthermore, and at a similar operating temperature; the diesel range hydrocarbons (C10–C19) were around 66% of the total fuel like chromatograph studied for the pyrolysis oils. The work in this study and based on properties of fuel investigated point towards blending the oil extracted with conventional fuels that could result in lowering dependency on fossil based ones. Further upgrading is also possible whereby desulphurisation could lead to renewable and sustainable fuel source utilising a solid waste feedstock such as ELTs.

Biochar has recently proven to be effective in various applications including soil amendment for crop production and removal of pollutants from the contaminated water and soil environments. However, major studies on the alterations in bulk density, porosity, water holding capacity, acidity and mineral content of the soils due to the addition of biochar have been carried out in lab-scales. Innumerable studies have investigated the properties of the biochar prepared from various feedstocks under various pyrolysis conditions to examine the effect of peak operating temperature, heating rate and residence time. To promote the commercialization of biochar for large-scale applications, there is a need for critical discussion on the advantages and disadvantages of the biochar for various soil applications (e.g., soil amendment and/or decontamination) in terms of technical, environmental, economic and social considerations. To address this urgent need, the present review attempts to evaluate the application of biochar for soil amendment within the framework of sustainability and recommendations for the future research and applications of biochar for soil treatment.

Accurate prediction of solid waste (SW) generation is considered an important aspect of waste management. It plays a major role in strategy development especially in developing countries. In this work, six independent variables related to the state of Kuwait were used as inputs for the development of multi-variable regression models. The aim was to predict SW generation rates from a number of sectors within the country, namely the domestic, commercial, building and construction (B&C), and agricultural ones. The variables included comprised the total population of the country, gross domestic product (GDP) index, construction area, cost of utilised constructed agricultural area and total agricultural production requirements. Statistical analysis was used to confirm the reliability of the regression models developed. The results indicated that predications were highly accurate with standard errors (SE) ranging between 3.52% and 10.46% for the indicators of the multiple regression predictive models. Multiple-variable regression models developed showed mean standard errors ranging between 0.125 and 1.09% for the dependent variables considered. The developed regression models can be used to predict individual SW components which could be used by decision makers when devising measures and policies for long-term SW management strategies.

The demand for energy is continuously increasing worldwide. This places a constant strain on the production and availability of fossil fuels on which most current energy sources are based. Thus, alternative sources of energy (non-fossil based) are urgently needed to produce liquid fuels. However, conventional technologies and reactors used for these alternative processes have been associated with low mass and heat transfer rates, long reaction times and extreme temperatures and pressures. To address these limitations, microreactors have been developed and utilised over the past decade, and have been proven to increase product yields and reduce residence time and product selectivity when compared to conventional reactors. This paper provides an in-depth review of the liquid fuel production routes over the last decade, and highlights the advantages of microreactors that have been successfully employed to overcome some of the issues faced with conventional bulk reactors.

The study focusses on using virgin grades of low and linear low density polyethylene for pyrolysis route of fuel production, in order to mimic the most common municipal plastic waste components as a desirable feedstock with the future aim of integration plans to petroleum refining and petrochemical industries. The oil produced was assessed for basic properties of fuels and insights are provided as to fuel range of common fossil fuel types that it can replace. Effect of reactor temperature and oil yield characteristics was studied and the maximum oil yield (27%) was obtained at 600 °C while higher temperatures (700 and 800 °C) increased the diesel fraction in the pyrolysis oil. It is found that the diesel range hydrocarbons were the most abundant with the highest total sum for samples extracted from low density polyethylene pyrolysis oil. The oil produced is highly desirable and applicable as a fuel with a cetane number of 84. The oils in this work has low aromatic content likely retained by the thermal cracking process in the gaseous product fraction. The flash point measured for the oil samples (80 °C) agree with market standards for diesel fuel. The pour point, however, was slightly higher (10 °C) still making it suitable to be used a diesel.

Gas Chromatography coupled with Mass Spectrometry (GC/MS) has been applied in various analytical chemistry works. However, to fine tune a system that can serve the purposes of pyrolysis oil identification has proven to be a laborious effort, especially when considering the fact that no standard protocol exists for such analysis. In addition, obtained products were yielded from a newly commissioned unit with a unique and novel design. In this study, a US patent office claimed reactor [SULTAN-1, Pyrolysis Reactor System for the Conversion and Analysis of Organic Solid Waste, Patent application number: 15,487,351] that degrades polyolefinc virgin and waste materials to obtain petroleum refinery and petrochemical feedstock, has been commissioned. The reactor produces three distinct physical states of matter products accumulated as testing specimens, i.e. solids, gaseous and oil. The samples analysed in this work were of the gas and oil produced by pyrolysis of end of life tyre (ELTs) shavings that required to have a special recipe to work with in the laboratory. Various MS cords were utilised and experimental setups to fine tune the process, and special emphasis was given on the gas samples variation in this communication. To reach the desired analysis results with high repeatability, a plethora of experiences of lab personnel and laboratory-based experimental work was accumulated. Laboratory protocols were also setup for this work. These will be detailed along the process execution which yielded a standard laboratory best practice analytical method as part of the State of Kuwait newly initiated Government Initiative project.

The objective of this work is to study the thermal degradation kinetic parameters of polypropylene (PP) and compare them to those of a polypropylene/starch blend (PP/S) (70/30 (wt %)), taking into account the effect of photodegradation caused by natural weathering. Samples were taken from tree shelters exposed to four years of natural weathering and compared to the unexposed material stored under laboratory conditions. Nonisothermal (dynamic) thermogravimetery was used with five different heating rates (β): 5, 10, 15, 20, and 25 °C min–1. Several analytical model-free methods were used to determine the kinetic parameters, including the Friedman, Coats and Redfern, Kissinger, and Flynn–Wall–Ozawa (FWO) methods. The model-fitting method of Criado was also applied to determine the optimal mechanism of degradation that the polymers followed. In addition, an analytical solution was developed to mathematically model the experimental data and estimate the kinetic parameters. The analytical approach was developed...

Plastic article with pro-oxidant additives have been commercially used within the past decade and promoted to be an environmentally sound option to mitigate plastic solid waste (PSW) accumulation. These products also present a dispute as to the manner they should be standardised by various international bodies. One of which, is the biotic influence on such products where their degree of degradation is studied. In this work, the standard test method of ASTM D 5988 ‘Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in Soil’ has been applied on three commercial grade oxo-biodegradable polyethylene (PE) film products. The performance of the tested specimens was measured against local soil secured from an arid site within the State of Kuwait mimicking local landfill conditions. The carbon dioxide generation was estimated and the rate of biodegradability was estimated as per the suggested methodology in the test protocol. It was noted that the carbon content was independent of the rate of carbon evolution and was attributed to the pro-degradant and heavy metal content present in the plastic product. The work in this communication can pave the way for the future consideration for this test procedure to be part of the standards in the developing world to mitigate their solid waste (SW) accumulation problem.

This chapter discusses one of the main technologies and focus of various research groups around the world concerned with plastics transformation to energy, fuel, and chemicals. This chapter details the thermo-chemical treatment process of pyrolysis, which is discussed in great depth within this work. The influence of various operating conditions is detailed as well. What makes this chapter quite unique is that it illustrates the opportunities that this process presents. It shows how certain parameters can influence the performance of pyrolysis, and how certain modes of operation are preferred to others when different types of plastics are being treated. It showcases the influence of the operational parameters that one should consider when pyrolysis is in question, from operating pressure, to temperature, to feedstock type manipulation. This chapter can be considered as a comprehensive review that shows how research in this area has advanced in the past few decades, with emphasis on development in pyrolysis technology, and details regarding the unique results and perspectives of its implementation on plastics treatment. It also depicts technologies and techniques on various scales including examples from industry. The chapter also does not neglect advances in this technology, in particular, detailing new and emerging technologies in this field. Also, distinction from other similar technologies is emphasized and presented in depth for the reader’s concern. The products obtained from this process are given, in particular, with respect to various feedstock materials. The chapter also attempts to distinguish the various terms and types of thermal technologies used for plastics treatment by providing the reader with categorization systems and definitions that are common in this area of study.

Polymers will degrade under certain operational conditions. To do so, a certain amount of energy is required. By studying influencers on this process, one can go deep into the behavior of the material when exposed to certain operational parameters. The reaction kinetics of the degradation reaction can provide numerous advantages. It can point towards the material’s stability under various thermal conditions, determine required energy to degrade a certain polymers (or a mix of polymers), intensify product yields, establish the mechanism of degradation, and consequently, design units that can treat the materials for specific applications. This chapter provides the reader with the ultimate guide for the study of polymer degradation reaction kinetics. It presents the principles by which the kinetic triplet (i.e., activation energy, preexponential factor, and reaction order) can be estimated for various types of setups. Dynamic and isothermal measurements are explained in the context of degressive reaction expressions, where methods established for the determination of the kinetic parameters are illustrated. Limitations and drawbacks of these methods are also explained, and a case study from literature is also used to depict the principles established.

There exists a number of techniques that have been developed into well-established technologies to recover chemicals and fuel from plastics. The objective has always been twofold: to recover valuable chemical products from polymeric materials deemed as waste, and to have a large proportion of these chemicals to represents a fuel mix that can replace fossil-based fuels. In this chapter, a very comprehensive review is given to such technologies at various scales, where plastics are used as a feedstock material to produce valuable chemicals and fuels. The majority of these techniques have been developed into well-established technologies. On the other hand, some are still at research and development stages to date. The chapter serves as a guide to these technologies, taking the reader into the major concepts and principles of how plastic materials can degrade to such chemicals. The chapter also starts with a guide to some of the major concepts typically encountered in this field of work. These include heating values and energy content. This is done to give the reader a comprehensive view of the description of these methods which will be encountered in later stages of this book. To describe these technologies and major recovery techniques, the plastic solid waste management hierarchy is also detailed. This was done to convey the main routes of recovery for plastic materials, and to show how these technologies can serve as a route for fuel recovery via thermo-chemical and thermal means.

Energy production, or recovery, is a broad term that is typically used to cover a wide range of technologies and processes which will render the material being treated as a fuel to produce power, steam, or heat. The concept of energy recovery has been predominately associated with waste management technologies, covering a wide range of processes such as: landfill gas generation, biogas generation from organic waste, thermolysis, and feedstock recycling for fuel production and incineration. However, the most commonly associated technology of energy recovery from waste materials has always been incineration in a waste to energy (WtE) context. This chapter details the key concepts of this technology that is considered to be the most widespread technique in energy production from waste. Not only that, but incineration units are typically the most applied technology of waste management, and are certainly the most common treatment of plastics. The chapter starts with a general introduction to the incineration and combustion science principles. The main controlling parameters of incineration units are detailed, where feedstock characteristics and applicability for incineration are discussed. The chapter then goes on to depict the main incineration unit types found in the management of waste that can be used in the treatment of municipal and plastic solid waste. The main types of units where given in order of popularity. The main design concept and process operation are also detailed. The units discussed in this chapter are rotary kiln incinerators, moving grate technology, fluidized bed combustors, multiple hearth incinerators, and electric infrared incinerators. These units were chosen as they represent the most common technologies that will result in an ideal plastics treatment process for energy recovery. The principles whereby energy recovery is achieved by incineration is also explained. The main polluting chemicals and airborne emission control (considered as a burden on the environment) are also detailed in this chapter.

This chapter delivers two main parts that are essential in understanding associated concepts within the plastics degradation to energy and fuels domain, which are the environmental and economical challenges that are associated with such processes. The chapter reviews the main environmental criteria and what poses as operational and environmental challenges to such processes, when a concerned party is interested in commissioning them. The environmental burdens are accounted for and what is typically used as a tool to determine the most beneficial process (environmental) is explained. This tool is life cycle assessment (LCA), which is explained in the interest of this chapter and the book as a whole, as it provides the ultimate means of determining the best practice and optimal scenario of treatment when unit operation and products evaluation is under consideration. The types of LCA studies are also explained, and various examples and milestones achieved within research circles are demonstrated. Two case studies are also given in great detail in this chapter. The first shows the LCA study of two processes that use plastics as a feedstock for producing energy and fuels. It accounts for the environmental burdens of these processes when compared with conventional routes of treatment for similar feedstock. The second is concerned with the determination of the health impact of a plastic to power generation facility. Socioeconomic and economical factors associated with plastics to energy and fuels processes are also explained and detailed for the reader’s interest.

Microplastics (MP), the debris that collectively refers to plastic fragments and particles of