This paper reviews the global status of waste to energy (WTE) technologies as a mean for renewable energy production and municipal solid waste (MSW) disposal method. A case study of the Kingdom of ...Saudi Arabia (KSA) under this concept was developed. The WTE opportunities in the KSA is undertaken in the context of two scenarios: (1) incineration and (2) refuse derived fuel (RDF) along with biomethanation from 2012 to 2035. Biomethanation technology can proved to be the most suitable WTE technology for KSA due to (a) availability of high food waste volume (37% of total MSW) that can be used as a feedstock, (b) higher efficiency (25–30%) and (c) lowest annual capital ($0.1–0.14/ton) and operational cost. However, the need for large space for continuous operation might increase operational cost. The RDF has an advantage over incineration due to (a) less annual capital ($7.5–11.3/ton) and (b) operational cost ($0.3–0.55/ton), but the high labor skills requirements will most probably be a limitation, if appropriate training and related infrastructure are not scheduled to be included as a prerequisite. The incineration technology also proves to be an efficient solution with a relatively higher efficiency (25%) and lower operational cost ($1.5–2.5/ton). However, the need for treatment of air and waterborne pollutants and ash within the incineration facility can be the limiting factors for the development of this technology in KSA. In 2012, the power generation potential for KSA was estimated at 671MW and 319.4MW from incineration and RDF with biomethanation scenarios respectively, which was forecasted to reach upto 1447MW and 699.76MW for both scenarios respectively by 2035. Therefore, WTE technologies, could make a substantial contribution to the renewable energy production in KSA as well as alleviating the cost of landfilling and its associated environmental impacts. However, the decision to select between the two scenarios requires further in-depth financial, technical and environmental analysis using life cycle assessment (LCA) tool.
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•Steam-oxygen gasification produced syngas containing maximum H2 up to 40%.•Combustion efficiency reached up to 98–99% at 800–850 °C.•The CO concentration was 9–15 ppm in enriched ...oxygen fuel combustion.•Combined air gasification and EFGT targeted the highest exergy efficiency 37.1%.•The highest overall efficiency of combustion technology CLOF-CCS was 35.7%.
Gasification and combustion processing is deemed reliable and feasible methods in response to concerns about landfilling – a traditional treatment due to rapid growth in disposal capacity and pollution. In gasification and combustion processing, various processes are integrated with different configurations to carry out energy conversion of the thermal treatment process and improve the energy recovery efficiency. This study aimed to propose an effective solution to waste treatment by considering the sustainability and economic perspectives. This paper provided the observation on the technical perspectives of the gasification and combustion processes: the properties of sludge, reactor, combustion or gasification media and operating conditions applied to sewage sludge treatment. In addition, the application of the thermodynamic cycle with various heat recovery strategies for electricity generation was summarized in this paper. According to the research data, sewage sludge combustion efficiency reached up to 99 % at the combustion temperature of 800–850 °C. The maximum hydrogen gas (H2) content was recorded at 40 mol% under steam/oxygen gasifying agent, and the low heating value of syngas was 6–7 MJ/Nm3 for sewage sludge gasification. The integration between air gasification, external fired gas turbines (EFGT) without carbon capture process showed the highest exergy efficiency at 37.1 %, which was higher than 35.7 % resulted from waste combustion technology.
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•Discussed waste-to-energy methods for the treatment of municipal solid waste (MSW).•Examined the energy recovery possibilities of China's municipal solid waste.•A comparison between ...Chinese provinces and chosen developed regions is made.•Evaluated conventional and unconventional solutions for reclaiming energy from MSW.
To realize the management of municipal solid waste (MSW), China uses MSW conversion technology to generate fuel and other byproducts through which the operating costs (e.g., capital and operational) are maintained to some extent. The amount of MSW produced per capita in China is a serious problem. Therefore, a circular economy method was investigated that can not only manage MSW safely but also convert MSW into energy to meet the growing energy demand. This study summarized the current status of MSW treatment and gives an overview of several waste-to-energy conversion technologies by describing their possible and existing situation in China and identifying related challenges. Currently, none of the single technologies can effectively realize waste-to-energy conversion. Only in this way can waste-to-energy technology achieve commercial success and community preparedness.
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•The current status, options and challenges of WTE techniques were analysed.•Incineration is the most widely used WTE technology in the developed countries.•Landfilling is the most ...common practice of MSWM in developing countries.•Approximately 50 million tonnes of methane is emitted annually from landfills.•WTE will ensure both the energy security and environmental protection.
Approximately one-fourth population across the world rely on traditional fuels (kerosene, natural gas, biomass residue, firewood, coal, animal dung, etc.) for domestic use despite significant socioeconomic and technological development. Fossil fuel reserves are being exploited at a very fast rate to meet the increasing energy demands, so there is a need to find alternative sources of energy before all the fossil fuel reserves are depleted. Waste to energy (WTE) can be considered as a potential alternative source of energy, which is economically viable and environmentally sustainable. The present study reviewed the current global scenario of WTE technological options (incineration, pyrolysis, gasification, anaerobic digestion, and landfilling with gas recovery) for effective energy recovery and the challenges faced by developed and developing countries. This review will provide a framework for evaluating WTE technological options based on case studies of developed and developing countries. Unsanitary landfilling is the most commonly practiced waste disposal option in the developing countries. However, developed countries have realised the potential of WTE technologies for effective municipal solid waste management (MSWM). This review will help the policy makers and the implementing authorities involved in MSWM to understand the current status, challenges and barriers for effective management of municipal solid waste. This review concluded WTE as a potential renewable source of energy, which will partly meet the energy demand and ensure effective MSWM.
•A waste-to-energy hybrid system for power and heat cogeneration is designed.•Integration of plasma gasification, SOFC, gas turbine and supercritical CO2 cycle.•The system has waste-to-electricity ...efficiency of 59.30% and exergy efficiency of 56.40%•Plenty of economic benefits can be excepted within a short payback period.•Achieving efficient, clean and economic conversion from hazardous waste to energy.
In this paper, a novel scheme consisting of plasma gasifier, solid oxide fuel cells (SOFC), gas turbine (GT), and supercritical CO2 cycle has been developed for power and heat cogeneration. Fed by syngas converted from medical waste through plasma gasification, the new design is a SOFC-GT hybrid system benefiting from supercritical CO2 cycle to enhance its performance. Besides, the waste heat carried by the low-temperature exhaust gasses and CO2 stream is further exploited for providing domestic hot water to residents. The benefits of the suggested system were examined based on a 3 t/h plasma gasifier in the thermodynamic and economic aspects, and the effects of the main parameters were also investigated. It is found that the net power output of the studied system could reach up to 14.02 MW with a net waste-to-electricity efficiency of 59.30% and an exergy efficiency of 57.56%. The main source of irreversibility can be traced to three components, gasifier, cell stacks, and afterburner, accounting for 62.45% of the total exergy destruction. Only 3.77 years is required to recover the initial investment of the proposed system and a net present value of 109815.39 k$ can be attained by the waste-to-energy project during its 20-year lifespan.
A novel medical-waste-to-energy design combining plasma gasification (treating medical waste) and municipal solid waste (MSW) incineration has been developed. In the integrated system, the syngas ...generated by the plasma gasification of medical waste is first burned and drives the gas turbine for power generation, subsequently, the gas turbine exhaust is taken to heat the live steam and feedwater of the MSW incineration plant, improving the power cycle of the incineration plant. Consequently, medical waste can be converted into electricity efficiently in the meantime of harmless management. The hybrid design was investigated by multiple approaches including energy analysis, exergy analysis, and economic analysis. It is found that the energy efficiency and exergy efficiency of medical-waste-to-electricity can reach up to 37.83% and 34.91% with a net total power of 4.24 MW yielded from medical waste, while the net power generated from MSW is considered fixed. Besides, the proposed medical-waste-to-electricity project has a short dynamic payback period of 3.75 years and the relative net present value can achieve 45,239.90 k$. These results demonstrate that the novel concept is efficient, feasible, and advantageous, which is promising to be implemented in the field of waste-to-energy.
•A novel medical-waste-to-energy design based on plasma gasification is proposed.•The medical-waste-based power process is integrated to an incineration power plant.•The fly ash collected from MSW incineration is treated together with medical waste.•The medical-waste-to-electricity efficiency can reach up to 37.83%.•The dynamic payback period is only 3.75 with a net present value of 45,239.90 k$.
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•Wastes to hydrogen was studied for both energy and environmental benefits.•Application of data-driven approaches for aiding SCWG process was investigated.•Machine learning based ...predictive and optimization models were developed.•Catalyst descriptors and critical process factors based on feature engineering were revealed.•Optimal experimental conditions and catalysts for SCWG of wet wastes were identified.
Hydrogen production from wet organic wastes through supercritical water gasification (SCWG) promotes sustainable development. However, it is always time-consuming and expensive to achieve optimal SCWG conditions and suitable catalysts for different wastes to produce H2-rich syngas. Herein, we developed a unified machine learning (ML) framework to predict syngas composition from SCWG processes inclusive of non-catalytic and catalytic systems. The neural network (NN) model which was the core of the framework exhibited generalizable and satisfactory accuracy (R2 > 0.85) for all systems evaluated. The model also aided in the screening of catalyst and provided optimal conditions for accelerating experiments to produce H2-rich syngas by maximizing H2 yield and minimizing CO2 yield. ML model-based exploration found that SCWG temperature and solid content in the feedstock were the two most important factors affecting syngas composition. ML-based optimization suggested that Fe-based catalyst exhibited a greater potential to promote SCWG of wet wastes under optimal operational conditions. Besides, a web-based graphic user interface was developed by embedding the developed NN model for free access to the SCWG scientific community.
The environmental risks of conventional waste disposal methods, along with the resource and energy value of waste, have formed the foundation for waste-to-energy (WtE) technology. WtE systems that ...work on recovering energy present a suitable solution to generate energy and sustainably manage waste. This type of waste management system in the Middle East and North Africa (MENA) region is still considered underutilized as WtE technology is rarely used due to a lack of experience in their specific local conditions, lack of qualified competencies, and the absence of an appropriate regulatory and legislative structure. This study reviews the existing WtE policies and regulations, and it investigates the potential of WtE techniques in the MENA region. Moreover, sustainability in water consumption is critical; therefore, various water-conservation techniques were reviewed and considered when selecting regulatory actions. The radiative sky cooling technique was recommended to reduce water consumption. Barriers to implementing WtE and solutions for developing countries were presented to enable proper WtE implementation.
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•WtE plants provide a sustainable solution to waste management and energy generation.•Regulations that govern WtE activities are essential to WtE implementation in developing countries.•Developing countries face barriers that hinder the implementation of WtE plants.
•Critical review of 136 journal articles with 250 WtE case-study LCA scenarios.•Case-studies are assessed in detail with respect to critical LCA modelling aspects.•Key results and conclusions from ...the reviewed studies are highlighted.•Critical shortcomings in the studies are identified and recommendations provided.
Life cycle assessment (LCA) has been used extensively within the recent decade to evaluate the environmental performance of thermal Waste-to-Energy (WtE) technologies: incineration, co-combustion, pyrolysis and gasification. A critical review was carried out involving 250 individual case-studies published in 136 peer-reviewed journal articles within 1995 and 2013. The studies were evaluated with respect to critical aspects such as: (i) goal and scope definitions (e.g. functional units, system boundaries, temporal and geographic scopes), (ii) detailed technology parameters (e.g. related to waste composition, technology, gas cleaning, energy recovery, residue management, and inventory data), and (iii) modeling principles (e.g. energy/mass calculation principles, energy substitution, inclusion of capital goods and uncertainty evaluation). Very few of the published studies provided full and transparent descriptions of all these aspects, in many cases preventing an evaluation of the validity of results, and limiting applicability of data and results in other contexts. The review clearly suggests that the quality of LCA studies of WtE technologies and systems including energy recovery can be significantly improved. Based on the review, a detailed overview of assumptions and modeling choices in existing literature is provided in conjunction with practical recommendations for state-of-the-art LCA of Waste-to-Energy.
Plastics are common in our daily lifestyle, notably in the packaging of goods to reducing volume, enhancing transportation efficiency, keeping food fresh and preventing spoilage, manufacturing ...healthcare products, preserving drugs and insulating electrical components. Nonetheless, massive amounts of non-biodegradable plastic wastes are generated and end up in the environment, notably as microplastics. The worldwide industrial production of plastics has increased by nearly 80% since 2002. Based on the degree of recyclability, plastics are classified into seven major groups: polyethylene terephthalate, high-density polyethylene, polyvinyl chloride, low-density polyethylene, polypropylene, polystyrene and miscellaneous plastics. Recycling technologies can reduce the accumulation of plastic wastes, yet they also pollute the environment, consume energy, labor and capital cost. Here we review waste-to-energy technologies such as pyrolysis, liquefaction and gasification for transforming plastics into clean fuels and chemicals. We focus on thermochemical conversion technologies for the valorization of waste plastics. This technology reduces the diversion of plastics to landfills and oceans, reduces carbon footprints, and has high conversion efficiency and cost-effectiveness. Depending on the conversion method, plastics can be selectively converted either to bio-oil, bio-crude oil, synthesis gas, hydrogen or aromatic char. We discuss the influence of process parameters such as temperature, heating rate, feedstock concentration, reaction time, reactor type and catalysts. Reaction mechanisms, efficiency, merits and demerits of biological and thermochemical plastic conversion processes are also discussed.
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