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Torrefaction was applied to enhance the fuel properties of sawdust (SD) and bark wood (BW), biomass wastes from the rubberwood processing industry. Design Expert (DE) software was used in an experimental design to study the effects of affecting factors including torrefaction temperature and time as well as the biomass size towards the desirable properties such as HHV, mass yield, fixed carbon content, and eco-efficiency values. Promising results showed that the HHVs of the torrefied SD (25 MJ/kg) and BW (26 MJ/kg) were significantly increased when compared to preheated SD (17 MJ/kg) and preheated BW (17 MJ/kg) and in a range similar to that of coal (25–35 MJ/kg). The TGA, FTIR, biomass compositions, and O/C ratios suggested that thermochemical reactions played a significant role in the torrefaction at which thermal degradation coupled with possible in situ chemical reactions took place, to some extent. The optimal conditions of the torrefaction were identified at 320 °C and 30 min for SD, and 325 °C and 30 min for BW. The maximum HHVs at the optimal condition were 22, 23, and 20 MJ/kg while the eco-efficiency values were 29.18, 27.89, and 13.72 kJ/kg CO2_eq*THB for torrefied SD, torrefied BW, and coal, respectively. The findings of this study indicate that torrefied rubberwood residues enhanced HHV, eco-efficiency, and less contribution to CO2 emissions compared to fossil fuels.

This review examines the potential of municipal solid waste (MSW) as a renewable energy source, focusing on recent advances in thermochemical conversion technologies and their environmental impacts. The exponential growth of urban populations has led to a surge in MSW, necessitating sustainable waste management solutions. Traditional disposal methods, such as landfilling and incineration, have significant environmental drawbacks. However, advancements in waste-to-energy (WtE) technologies, including incineration, pyrolysis, and gasification, offer promising alternatives for energy recovery and resource utilization. This review explores the composition of MSW, its classification as a renewable resource, and the thermochemical conversion technologies that transform waste into energy. The environmental impacts of these technologies, particularly emissions and air quality concerns, are critically analyzed. The review highlights the evolving regulatory landscape and the implementation of advanced emission reduction systems. The findings underscore the importance of integrating innovative waste management strategies to promote a circular economy and achieve sustainable development goals.

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.

Food loss (FL) and food waste (FW) have become severe global problems, contributing to resource inefficiency and environmental degradation. Approximately 6% of greenhouse gas emissions (GHGs) are derived from FW, which is usually discarded in landfills, emitting methane, a gas that is 28 times more harmful than CO2. Diverting the path of FW towards the energy industry represents a promising avenue to mitigate the environmental impact and save resources while generating energy substitutes. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) approach was utilized to conduct a systematic literature review on 10 different conversion processes used to convert FL and FW into energy. Anaerobic bioconversion integrated with pyrolysis emerges as a potential eco-friendly and promising solution for FW management, nutrient recovery and energy production in various forms, including biogas, heat, biohydrogen and biochar. Despite its potential, the anaerobic digestion of FW still faces some challenges related to the production of intermediate harmful compounds (VOCs, NH3, H2S), which necessitate precise process control and optimization. Nonetheless, converting FW into energy can provide economic and environmental benefits in the context of the circular economy. This review offers insightful information to stakeholders, academics and policymakers who are interested in utilizing FW as a means of producing sustainable energy by summarizing the important findings of ten different waste-to-energy processing methods and their potential for improved energy recovery efficiency.

This paper puts forward a generic methodological framework to holistically assess WtE technologies based on the PROMETHEE approach. In addition to environmental and economic aspects, the method focuses on large-scale applicability and social preference, thus adopting economic, environmental, social, and technological criteria. Three data sources are selected, namely the scientific literature, a public survey, and an experts’ opinion survey, which is a novel combination with the aim to cover public consensus, technological applicability, and to provide alternative data sources for the economic and environmental criteria, thus enriching the methodology with the input of location specific data. The demonstration of the applicability of the proposed methodology is realized at a national level for the case of Greece. Anaerobic Digestion is shown to be the most preferable choice, recognized for its cost-effectiveness and lower environmental burden to other WtE technologies (i.e., gasification, pyrolysis, incineration). When all criteria are evaluated with equal weights, anaerobic digestion greatly outperforms incineration (net flow 0.833 versus 0.1667), while incineration only becomes the most preferred choice if the social criterion is in high focus (i.e., over 63% weight).

The search for cleaner and more sustainable energy sources is increasingly growing. Aligning this demand with another environmental problem, such as sewage treatment/disposal, is a strategic priority. In light of this, the aim of this study was to estimate the energy potential of sewage generated in the Brazilian state of São Paulo (SP) by using it to produce biomethane. The study also evaluated the viability of using this byproduct of sewage treatment (biomethane) as a substitute for natural gas (NG), as both of them have similar lower heat values. To do this, information was gathered regarding the population, gross domestic product per capita, sewage collected, and natural gas consumption for each of the state’s 645 cities, and, based on this, the sewage energy potential, the amount of NG to be substituted by biomethane, and the reduction in CO2 emissions were calculated. Moreover, in order to address a possible allocation of biomethane that could potentially be produced in each SP city and sent to currently NG-consuming cities, an optimization algorithm was proposed. The results indicated a sewage energy potential of 4.68 × 109 kWh/yr for the entire SP state, which would be enough to supply around 10% of the energy value of all the NG currently consumed. It was also observed that from 130 cities with NG consumption, 10 could produce enough biomethane to fully satisfy the natural gas demand. In the elected scenario of optimization, 291 cities were found to be capable of supplying the demand of 26 cities that currently use NG. The potential to reduce CO2 emissions is between 1.81 × 106 and 2.42 × 106 ton/yr, and this range could increase if sewage treatment coverage grows. Despite the challenges inherent in extrapolating a potential study to scenarios that require significative investment, the results obtained are useful for formulating public policies for decarbonization in the near future.

Poland is highly likely, as per a European Commission report, to fall short of meeting the 2025 targets related to the preparation for re-use and recycling of municipal waste and packaging waste. The risk of not meeting the municipal waste recycling targets stands at 27%, while for packaging waste, it is estimated at 30%. Recycling rates play a pivotal role in gauging the efficiency of waste management systems, as well as in monitoring progress toward a circular economy. Taking into account the considerable likelihood of Poland not achieving the recycling targets, the authors of the paper found it imperative to identify the risk factors associated with Poland’s failure to meet the European Commission’s recycling and landfill targets within the waste-to-energy context. Additionally, they sought to evaluate the potential for the development of the waste-to-energy concept in Poland. The research objectives were fulfilled through the literature review method. By employing the classification of factors outlined in a SWOT analysis, the authors highlighted which of the identified risk factors could or should be considered strengths or weaknesses, opportunities or threats to the Polish recycling process. Mapping out future courses of action will enable decision-makers in Poland to address the weaknesses in recycling, capitalize on opportunities arising from the socio-economic situation in Poland, and formulate plans to mitigate the identified threats. Undertaking such initiatives has the potential to enhance recycling rates in Poland and facilitate the broader application of waste-to-energy practices.

Despite their key role in integrated waste management, direct (incineration) and indirect (gasification/pyrolysis) waste combustion processes are still opposed by some of the general public due to the past emission levels of air pollutants. In fact, although the release of air pollutants (especially dioxin) to the atmosphere from waste combustion processes has gradually decreased over the years, thanks to the introduction of stricter regulations and more advanced removal technologies, there is still an unsolved problem regarding the public acceptance of waste-to-energy facilities. The aim of this paper is to provide an overview of the state-of-the-art air pollution control (APC) technologies used in waste combustion facilities. Air pollution control technologies are designed to reduce or eliminate the emissions of harmful pollutants into the atmosphere. These technologies are important for safeguarding public health, protecting ecosystems, complying with regulations, and promoting a more sustainable and resilient future for both local and global communities. This paper will highlight the complexity behind emission control and the efforts made by this sector over the years. This paper will also propose suggested configurations based on the interactions/complementarity between different APC technologies and recent findings to improve their performance.

In this study, a technical analysis of synthesis gas (syngas) and biodiesel blend utilized in an internal combustion engine is presented. The experimental setup is composed of an engine workbench coupled with a downdraft gasifier which was fed with forest biomass and municipal solid waste at a blending ratio of 85:15, respectively. This research paper aims to contribute to the understanding of using fuel blends composed of synthesis gas and biodiesel, both obtained from residues produced in a municipality, since the waste-to-energy approach has been trending globally due to increasing waste generation allied with rising energy demand. The experiments’ controlling parameters regarding the engine are rotation and torque, exhaust gas temperature, and fuel consumption. The gasification parameters such as the oxidation and reduction temperatures, pressures at the filter, hood, and reactor, and the volume of tars and chars produced during the thermochemical process are also presented. Ultimate and proximate analyses of raw materials and fuels were performed, as well as the chromatography of produced syngas. The syngas produced from forest biomass and MSW co-gasification at a blending ratio in mass of 85:15 presented an LHV of around 6 MJ/m3 and 15% of H2 in volume. From the experiment using syngas and biodiesel blend in the engine, it is concluded that the specific consumption at lower loads was reduced by 20% when compared to the consumption of the same engine operating with regular diesel. The development of co-gasification of forest and municipal waste may then be an interesting technology for electrical energy decentralized generation.

The problems of environmental pollution caused by the operation of power plants and engines motivate researchers to develop new biofuels. The environmental aspect of composite biofuels appears to have great potential because of the carbon neutrality of plant raw materials. This study analyzes recent advances in the production of biofuels and their application. The research findings on the properties of promising plant raw materials and their derivatives have been systematized. The most important stages (spraying, ignition, and combustion) of using biofuels and mixtures based on them in internal combustion engines have been analyzed. A separate section reviews the findings on the environmental aspect of using new fuel compositions. Most studies show great prospects for involving bio-components in the development of composite fuels. The real issue is to adjust existing engines and plants to non-conventional fuel mixtures. Another big problem is the increased viscosity and density of biofuels and oils, as well as the ambiguous effect of additives on burnout completeness and emissions. The impact of the new kinds of fuels on the condition of components and parts of engines, corrosion, and wear remains understudied. The interrelation of industrial process stages (from feedstock to an engine and a plant) has not been closely examined for composite liquid fuels. It is important to organize the available data and develop unified and adaptive technologies. Within the framework of this review work, scientific approaches to solving the above problems were considered and systematized.

Waste-to-energy approaches, aimed at using cheap energy carriers (oil production and refining waste, etc.), require the creation of new technologies with high energy efficiency and low emissions. One of the environmentally friendly methods is a superheated steam injection (SIM) into the combustion zone. At the same time, trends in CO2 reduction and recycling make carbon dioxide more attractive to use together with, or instead of, steam. This paper experimentally investigated the possibility of upgrading SIM to steam and the carbon dioxide injection method (SCIM) or the carbon dioxide injection method (CIM), where superheated steam and carbon dioxide are supplied together or completely replaced by CO2. In the example of diesel fuel, the characteristics of the combustion of liquid hydrocarbons in the presence of a mixture of superheated steam with CO2 in a spray burner are obtained and compared. It shows that a high completeness of fuel combustion is observed for all the studied modes. The analysis of combustion product composition demonstrates that when replacing the superheated steam with carbon dioxide, the levels of CO and NOx in the combustion products increase by 25%. All the investigated regimes comply with the EN:267 standard. The results obtained show that it is possible to realize SCIM and CIM approaches for waste-to-energy with the use of CO2.

The management of municipal solid waste presents significant challenges globally. This study investigates the potential of an integrated waste-to-energy system based on circulating fluidized bed gasification technology to address these challenges, while also contributing to renewable energy generation. Using a MATLAB-based simulation model, the study determines the optimal operational parameters for various units within the system, including waste processing, gasification, ash handling, syngas treatment, and emission control. The proposed waste-to-energy system demonstrates a remarkable energy efficiency of 70% under these optimal conditions, notably outperforming conventional waste-to-energy technologies. Sensitivity and uncertainty analyses reveal that waste composition, gasification temperature, and the oxygen-to-solid recovered fuel ratio are key determinants of the system’s output and performance. The system’s performance remained robust despite variations in these parameters, underscoring its potential as a reliable solution for waste management and energy generation. While the findings are promising, future research should focus on comprehensive lifecycle assessment and consider regional factors for practical implementation. This study contributes to the ongoing development of efficient waste-to-energy systems and highlights their potential in promising sustainable waste management and renewable energy production.

The current focus on renewable energy sources and the circular economy favors the thermal conversion of low-quality fuels, such as biomass and waste. However, the main limitation of their usability in the power sector is the risk of slagging, fouling, ash deposition, and high-temperature corrosion. These problems may be avoided or significantly mitigated by the application of aluminosilicate clay minerals as fuel additives. In this paper, the three most commonly occurring aluminosilicates are reviewed: kaolin, halloysite, and bentonite. Their application has been proven to minimize combustion-related problems by bonding alkalis in high-melting compounds, thus increasing ash melting temperatures, reducing ash deposition tendencies, and decreasing the particulate matter emission. Due to excellent sorption properties, aluminosilicates are also expected to fix heavy metals in ash and therefore decrease their emissions into the atmosphere. The application of aluminosilicates as fuel additives may be a key factor that increases the attractiveness of biomass and other low-quality fuels for the power sector.

This research aims to compare, from a technical and financial perspective, the application of biological (methane-capture) and thermal (incineration) treatments of waste in Mexico City in order to generate clean energy. For each alternative, pessimist (50%), realistic (80%), and optimistic (100%) scenarios were considered in terms of the efficiency collection rates of methane and the efficiency of the capacity conversion factor for incineration. For the methane project, the LandGEM model was used to evaluate the potential generation of methane. In order to calculate the electricity output that could be generated through incineration, we relied on two key factors: the total amount of heat that could be generated by burning the waste and the average level of moisture in the waste material. The evaluation resulted in an annual energy generation of 206.09 GWh for methane and 4183.39 GWh for incineration, both in the realistic scenario. Both projects reported positive financial indicators with a discount rate of 12%. Incineration resulted in a net present value of USD 706,377,303 and an internal rate of return of 23% versus USD 4,975,369 and 24% for the methane project. However, the incineration project only became feasible by omitting financing. Incineration resulted in a payback period that was lower by a ratio of 2:1 compared to methane, but the levelized cost of energy resulted in higher figures (USD 216.92). The aim of these findings is to support the decision-making process for the creation and implementation of sustainable energy strategies based on circular economy principles in Mexico and other similar regions across the globe.

The eutrophication process, caused by the uncollected seaweed and macroalgae, is a relevant and ongoing ecological issue. In case this biomass is collected from the seashores, it could be used as a potential feedstock for recovery of higher-added-value energy products. This paper aims to investigate the seaweed perspective of uses as a potential feedstock in the slow-pyrolysis process, using microthermal analysis combined with Fourier transform infrared spectrometry and experiments at the laboratory scale at different temperatures with two different types of zeolite catalysts. The primary investigation was performed using a micro-thermal analyser, and the results revealed that seaweed thermally decomposes in two stages, at 250 and 700 °C, while the catalyst slightly decreased the activation energy required for the process, lowering the temperatures of decomposition. Experiments on a laboratory scale showed that the most common compounds in the gaseous phase are CnHm, H2, CO, and CO2. Nevertheless, the most abundant liquid fraction derivatives are substituted phenolic compounds, pyridine, benzoic acid, naphthalene, d-glucopyranose, and d-allose. Furthermore, the catalyst decreased the amount of higher molecular mass compounds, converting them to toluene (71%), which makes this technology more attractive from the recovery of higher-added-value products point of view.

This study assessed the energy potential, economic feasibility, and environmental performance of landfill gas (LFG) recovery, incineration, and anaerobic digestion (AD) technologies for Phnom Penh municipality in Cambodia, from 2023 to 2042. The economic analysis utilized the levelized cost of electricity (LCOE), payback period (PBP), and net present value (NPV) to evaluate the feasibility of each technology. Additionally, environmental performance was assessed following the IPCC 2006 guidelines. The results indicate that incineration produced the highest energy output, ranging from 793.13 to 1625.81 GWh/year, while the LFG and AD technologies yielded equivalent amounts of 115.44–271.81 GWh/year and 162.59–333.29 GWh/year, respectively. The economic analysis revealed an average LCOE of 0.070 USD/kWh for LFG, 0.053 USD/kWh for incineration, and 0.093 USD/kWh for AD. Incineration and LFG recovery were found to be economically feasible, with positive NPVs and a potential for profit within 8.36 years for incineration and 7.13 years for LFG. In contrast, AD technology had a negative NPV and required over 20 years to generate a return on investment. However, AD was the most promising technology regarding environmental performance, saving approximately 133,784 tCO2-eq/year. This study provides valuable technical information for policymakers, development partners, and potential investors to use in order to optimize waste-to-energy investment in Cambodia.

This paper evaluates the feasibility of bioethanol production from onion waste by Saccharomyces cerevisiae and Pichia pastoris and their novel co-culture through fermentation. The process parameters were optimized for each strain and their combination to observe the synergistic effect of co-fermentation. A dinitro salicylic acid (DNS) test was conducted to study the reducing sugar content of samples at different time intervals. Fourier transform infrared (FTIR) spectroscopic analysis was used to compare results for functional groups of samples before and after fermentation, and gas chromatography with flame ionization detection (GC-FID) analysis was performed to measure the bioethanol concentration obtained at different combinations of pH (5, 5.5, 6), temperature (20 °C, 30 °C, 40 °C), and time (24–110 h). The maximum bioethanol concentration was achieved through a monoculture of Saccharomyces cerevisiae, i.e., 30.56 g/L. The ethanol productivity was determined based on the ethanol concentration and fermentation time ratio. The energy content was determined using the obtained ethanol value and the specific energy content of ethanol, i.e., 30 kJ/g. The productivity and energy of bioethanol obtained at this maximum concentration were 0.355 g/L h and 916.8 kJ/L, respectively, after 86 h of fermentation at 30 °C and pH 5. Pichia pastoris produced a maximum of 21.06 g/L bioethanol concentration with bioethanol productivity and energy of 0.264 g/L h and 631.8 kJ/L, respectively, after 72 h of fermentation at 30 °C and pH 5. The coculture fermentation resulted in 22.72 g/L of bioethanol concentration with bioethanol productivity and energy of 0.264 g/L h and 681.6 kJ/L, respectively, after 86 h of fermentation at 30 °C and pH 5. The results of reducing sugars also supported the same conclusion that monoculture fermentation using Saccharomyces cerevisiae was the most effective for bioethanol production compared to Pichia pastoris and co-culture fermentation.

Waste-to-energy processes remain essential to ensure the safe and irreversible removal of materials and substances that are (or have become) unsuitable for reuse or recycling, and hence, to keep intended cycles of materials in the circular economy clean. In this paper, the behavior of inorganic compounds in waste-to-energy combustion processes are discussed from a multi-disciplinary perspective, against a background of ever tightening emission limits and targets of increasing energy efficiency and materials recovery. This leads to the observation that, due to the typical complexity of thermally treated waste, the intelligence of combustion control systems used in state-of-the-art waste-to-energy plants needs to be expanded to better control the behavior of inorganic compounds that typically end up in waste furnaces. This paper further explains how this goal can be achieved by developing (experimentally validated) predictive numerical models that are engineering-based and/or data-driven. Additionally, the significant economic potential of advanced thermochemical intelligence towards inorganic compounds in waste-to-energy combustion control systems is estimated on the basis of typical operational figures.

Waste-to-energy (WtE) is national policy. From this view, WtE technology has been promoted. Many WtE projects in Thailand were unsuccessful due to several problems. This research aimed to analyze the key barriers impacting the WtE project development in Thailand. The Interpretive Structural Model (ISM) and Cross-Impact Matrix Multiplication Applied to Classification (MICMAC) analysis tool have been used to evaluate the barriers that significantly in the development of WtE projects. In this study, WtE projects focused on electricity power generation in order to correspond to the Alternative Energy Development Plan (AEDP) target and power purchase agreement constrain of the government. The barriers were obtained from six sections consisting of social issues, environment, national policy, technology, economy, and project management. From six sections, there are 20 barriers that were identified. The ISM and MICMAC analysis showed that the key barriers impacting the WtE projects development were insufficient amount of waste and poor waste management planning. These two barriers correspond with many studies in Thailand and other countries. The project developers or investors must take these two barriers and other barriers with less impact mentioned in this study into account before developing the WtE projects in Thailand.

The use of waste incineration with energy recovery is a matured waste-to-energy (WtE) technology. Waste incineration can reduce the volume and mass of municipal solid waste significantly. However, the generation of high volumes of polluting flue gases is one of the major drawbacks of this technology. Acidic gases are constituents in the flue gas stream which are deemed detrimental to the environment. The wet flue gas desulphurization (FGD) method is widely employed to clean acidic gases from flue gas streams, due to its high efficiency. A major setback of the wet FGD technology is the production of wastewater, which must be treated before reuse or release into the environment. Treating the wastewater from the wet FGD presents challenges owing to the high level of contamination of heavy metals and other constituents. Membrane distillation (MD) offers several advantages in this regard, owing to the capture of low-grade heat to drive the process. In this study the wet FGD method is adopted for use in a proposed waste incineration plant located in Ghana. Through a mass and energy flow analysis it was found that MD was well matched to treat the 20 m3/h of wastewater generated during operation. Thermal performance of the MD system was assessed together with two parametric studies. The thermal efficiency, gained output ratio, and specific energy consumption for the optimized MD system simulated was found to be 64.9%, 2.34 and 966 kWh/m3, respectively, with a total thermal energy demand of 978.6 kW.

In this study, renewable and sustainable biofuel production from waste cooking oil and its blends with diesel fuel are investigated in terms of specific fuel properties. The fuel blends are named “Renewable Biofuel (RBF) 20” (20% biofuel–80% diesel), “Renewable Biofuel 50” (50% biofuel–50% diesel), and “Renewable Biofuel 100” (100% biofuel). The acid number, flash point, viscosity, cloud point, density, and pour point fuel properties of the new Renewable Biofuels are experimentally obtained and compared with diesel fuel. The viscosities of the biofuels are found to be 2.774 mm2/s for Renewable Biofuel 20, 3.091 mm2/s for Renewable Biofuel 50, and 4.540 mm2/s for Renewable Biofuel 100. Renewable Biofuel 20 has the minimum density value among biofuels. The density of Renewable Biofuel 20, Renewable Biofuel 50, and Renewable Biofuel 100 are obtained as 835 kg/m3, 846 kg/m3, and 884 kg/m3, respectively. More energy can be released with the use of Renewable Biofuel 100 in terms of heating value. The new fuel specification of biofuels can contribute to the fuel industry and help the studies on fuels for diesel engines.

The present study compiles a life cycle inventory for Ecuadorian sugarcane-derived ethanol production to quantify its environmental performance and identify the life cycle stages that cause major impacts. The scope of this study encompasses a cradle-to-gate analysis that includes the agriculture, the milling, the distillation, and the co-generation of electricity. This assessment is modeled using the OpenLCA v1.10.3 software. Two functional units (FU) were established in this study: “1 ton of sugarcane at-the-farm-gate” for the agricultural stage and “1 L of ethanol at-the-plant-gate”. A hybrid attributional and consequential life cycle analysis (LCA) approach has been followed. Economic allocation (EA) and system expansion (SE) were used to take co-products into account in the milling and co-generation of electricity stages, respectively. The co-generation stage is analyzed in three different scenarios: (i) average mix displacement scenario where the surplus electricity produced in the co-generation stage is displaced; (ii) marginal technology displacement scenario where the marginal surplus electricity is displaced from the mix and (iii) no displacement scenario. The global warming potential (GWP) impact at the farm gate level was reported as 53.6 kg of carbon dioxide equivalent (kg CO2eq.) per ton of sugarcane produced. The two main contributors of the agricultural stage correspond to N2O lixiviation and volatilization with 34% followed by the diesel used in agricultural machinery with 24%. The GWP for 1 L of ethanol produced was reported as 0.60 kg CO2eq. based on the average mix displacement scenario. No displacement scenario has a GWP impact of 0.84 kg CO2/liter of ethanol The distillation stage has the highest contribution to GWP impact with approximately 61% followed by the agricultural stage with 47%. The co-generation stage reports a contribution of −8.4% due to the surplus electricity displacement. The scenarios where the system expansion method is applied have a lower GWP impact compared to the scenario where no surplus electricity is displaced. Regarding terrestrial acidification potential impact, 0.01528 kg of SO2eq. was reported at the ethanol production level especially due to the nitrogen and phosphorous content in the vinasse produced from the distillation process. The marine eutrophication impact for 1 L of ethanol produced was 0.00381 kg of Neq. due to the content of nitrogen contained in the vinasse and the use of nitrogenous fertilizers in the agricultural stage. Finally, to create more eco-friendly Ecuadorian sugarcane and ethanol industries, sustainable and less polluting processes should be sought to reduce the environmental burdens. Companies should apply industrial symbiosis and circular economy strategies to produce lesser environmental loads within the ethanol production chain. The sugarcane industrial sector should also promote the surplus electricity production in order to gain credits.

The incineration process in waste-to-energy plants is characterized by high levels of inertia, large delays, strong coupling, and nonlinearity, which makes accurate modeling difficult. Therefore, an intelligent modeling method for the incineration process in waste-to-energy plants based on deep learning is proposed. First, the output variables were selected from the three aspects of safety, stability and economy. The initial variables related to the output variables were determined by mechanism analysis and the input variables were finally determined by removing invalid and redundant variables through the Lasso algorithm. Secondly, each delay time was calculated, and a multi-input and multi-output model was established on the basis of deep learning. Finally, the deep learning model was compared and verified with traditional models, including LSSVM, CNN, and LSTM. The simulation results show that the intelligent model of the incineration process in the waste-to-energy plant based on deep learning is more accurate and effective than the traditional LSSVM, CNN and LSTM models.

Sustainable biofuel production is the most effective way to mitigate greenhouse gas emissions associated with fossil fuels while preserving food security and land use. In addition to producing bioenergy, waste biorefineries can be incorporated into the waste management system to solve the future challenges of waste disposal. Biomass waste, on the other hand, is regarded as a low-quality biorefinery feedstock with a wide range of compositions and seasonal variability. In light of these factors, biomass waste presents limitations on the conversion technologies available for value addition, and therefore more research is needed to enhance the profitability of waste biorefineries. Perhaps, to keep waste biorefineries economically and environmentally sustainable, bioprocesses need to be integrated to process a wide range of biomass resources and yield a diverse range of bioenergy products. To achieve optimal integration, the classification of biomass wastes to match the available bioprocesses is vital, as it minimizes unnecessary processes that may increase the production costs of the biorefinery. Based on biomass classification, this study discusses the suitability of the commonly used waste-to-energy conversion methods and the creation of integrated biorefineries. In this study, the integration of waste biorefineries is discussed through the integration of feedstocks, processes, platforms, and the symbiosis of wastes and byproducts. This review seeks to conceptualize a framework for identifying and integrating waste-to-energy technologies for the varioussets of biomass wastes.

Reuse, refurbishing, and recycling are the most sustainable options for handling waste materials. However, for municipal solid waste (MSW) that is highly heterogenic, crude, contaminated, and decrepit, thermal conversion in waste-to-energy (WtE) plants is an option. In such plants, the fuel quality of MSW is difficult to predict and the substantial changes expected are challenging for incineration stability. Development of new online sensor technologies for monitoring waste properties prior to incineration is therefore needed. Sensors may contribute to increase WtE process stability, as well as reducing the probability of incineration stops or emissions exceeding legal limits. In this work, the operating principles of potential sensor systems for waste monitoring are categorized and assessed to be implemented for providing parameters for process control or indicators for process alarms in the waste incineration process. For transmissive settings, the use of inductance and hard X-ray sensors are most promising, whereas for reflective settings, utilization of photonic, inductive, soft and hard X-ray, as well as low-frequency radiowave sensors, are most promising. The analytic capacity of single-point measurements with inductance, radiowave, photonic, or X-ray sensors are limited to providing indicators for process alarms, whereas spectral imaging with X-ray or photonic techniques are feasible for providing parameters for both process control and indicators for process alarms. The results obtained in this sensor assessment will be important as a first step in guiding the evolution of monitoring waste properties in the WtE industry to increase repeatability, performance of energy production, and manual labor safety in controlling the waste incineration.

Municipal waste management in the EU has been challenged to a thorough transformation towards a Circular Economy. It is addressed by a number of quantitative policy targets, including a restriction on municipal waste landfilling to 10% in 2035. This paper presents the data on municipal waste composition in a large Polish city, based on thorough waste sorting analyses. On average, 374 kg of municipal waste is collected per capita in Wroclaw, of which 41% are separately collected fractions. The approach to implement the EU recycling targets until 2035 is presented, including an increase of sorting and recycling efficiency and a significant share of recyclables being retrieved from the residual waste fraction. Notwithstanding the recycling targets, an important stream of residual waste remains, amounting to 200 k ton in 2020 and approx. 130 k ton in 2035, which is available for energy recovery. The respective LHV values range from 8.5 to 7.6 MJ/kg. The results indicate that the residual waste stream, after satisfying the recycling targets, is still suitable for energy recovery through the whole period until 2035. Moreover, it is a necessary step towards closing the materials cycling in the municipal sector and the only option so far to reduce landfilling sufficiently.

Small Island Developing States (SIDSs) are faced with challenges such as reducing the share of fossil energy and waste landfilling. This work summarizes the main aspects of 53 SIDSs that constrain economic development, energy sources, and waste management strategies. An integrative bibliographical review is conducted to synthesize the state-of-the-art of waste-to-energy (WtE) strategies and compare the technologies in light of their suitability to SIDS. The findings show that considering the large amount of waste produced annually, WtE technologies are of the utmost importance to reduce ecological footprints (EFs) and greenhouse gas (GHG) emissions, and to increase the share of renewable energy with the installation of incineration plants with energy recovery to replace fossil fuel power plants. Although WtE is recommended for all SIDSs, the Atlantic, Indian Ocean, Mediterranean, and South China Sea (AIMS) countries exhibit higher population density (1509 inhab/km2) and a high share of fossil fuel in their electricity mix, so that there is greater urgency to replace landfilling practices with WtE. The estimation of potential power generation capacity (MWh) from annual municipal solid waste (MSW) in each SIDS as well as the reduced land area required demonstrate the feasibility of WtE technologies. Only 3% of the landfill area is necessary for buildings and landscaping associated with a WtE plant able to treat 1 million tons of MSW, considering a 30 year lifespan. Furthermore, incineration with energy recovery benefits from high penetration worldwide and affordable cost among thermochemical processes.

Using the thermalgravimetric technique, we investigated the non-isothermal combustion kinetics of abundant and low-cost date palm wastes (leaflet, rachis, fibers, and their composite) as potential biomass energy sources. The kinetic and thermodynamic parameters were determined by Flynn–Wall–Ozawa (FWO), Kissinger–Akahila–Sunose (KAS), and Starink methods. Thermogravimetric analysis results showed a major peak for the degradation of volatiles between 127–138 °C with average percentage mass loss of 68.04 ± 1.5, 65.57 ± 0.6, 62.97 ± 5.5, and 59.26 ± 3.2, for rachis, composite, leaflet, and fibers, respectively. The FWO model showed the lowest activation energy, Eα, of 157 ± 25.6, 158 ± 25.7, 164 ± 40.1, and 169 ± 51.8 kJ mol−1 for the composite, rachis, leaflet, and fibers, respectively. The positive enthalpy values confirmed an endothermic pyrolysis reaction. For all models, a minimal difference of 4.40, 5.57, 6.55, and 7.51 kJ mol−1 between activation energy and enthalpy for rachis, fibers, composite, and leaflet ensued, respectively. The KAS model was best suited to describe chemical equilibrium with average ΔG values of 90.3 ± 28.8, 99.3 ± 34.9, 178.9 ± 27.3, and 186.5 ± 38.2 kJ mol−1 for rachis, fibers, composite, and leaflet, respectively. The reaction mechanism by the Malek and Popescu methods was ((g(α)=[−ln(1−α)]14) across the conversion range of 0.1–0.9 for all heating rates. The high energy content and volatile matter combined with low energy barriers make date palm waste a potential candidate in a biorefinery.

In 2018, the production of Municipal Solid Waste (MSW) in EU-28 reached 250.6 Mt, with the adoption of different management strategies, involving recycling (48 wt %), incineration and thermal valorization (29 wt %) and landfilling (23 wt %). This work was based on the analysis of the baseline situation of MSW management in EU-28 in 2018, considering its progress in 2008–2018, and discussed the possible improvement perspectives based on a framework involving incineration and recycling as the only possible alternatives, specifically evaluating the capability of already-existing incineration plants to fulfill the EU needs in the proposed framework. The results of the assessment showed two main crucial issues that could play a pivotal role in the achievement of Circular Economy action plan targets: the need to increase the recycling quotas for specific MSW fractions through the separate collection, and therefore the improvement of definite treatment process chains; the optimization of the recovery of secondary raw materials from incineration bottom ash, involving the recycling of ferrous and nonferrous metals and the mineral fraction. Both issues need to find an extensive application across all member states to decrease the actual differences in the adoption of sustainable MSW management options.

Unless humanity achieves United Nations Sustainable Development Goals (SDGs) by 2030 and restores the relatively stable climate of pre-industrial CO2 levels (as early as 2140), species extinctions, starvation, drought/floods, and violence will exacerbate mass migrations. This paper presents conceptual designs and techno-economic analyses to calculate sustainable limits for growing high-protein seafood and macroalgae-for-biofuel. We review the availability of wet solid waste and outline the mass balance of carbon and plant nutrients passing through a hydrothermal liquefaction process. The paper reviews the availability of dry solid waste and dry biomass for bioenergy with CO2 capture and storage (BECCS) while generating Allam Cycle electricity. Sufficient wet-waste biomass supports quickly building hydrothermal liquefaction facilities. Macroalgae-for-biofuel technology can be developed and straightforwardly implemented on SDG-achieving high protein seafood infrastructure. The analyses indicate a potential for (1) 0.5 billion tonnes/yr of seafood; (2) 20 million barrels/day of biofuel from solid waste; (3) more biocrude oil from macroalgae than current fossil oil; and (4) sequestration of 28 to 38 billion tonnes/yr of bio-CO2. Carbon dioxide removal (CDR) costs are between 25–33% of those for BECCS with pre-2019 technology or the projected cost of air-capture CDR.

There is increasing interest in the harnessing of energy from waste owing to the increase in global waste generation and inadequate currently implemented waste disposal practices, such as composting, landfilling or dumping. The purpose of this study is to provide a modelling and simulation framework to analyze the technical potential of treating municipal solid waste (MSW) and refuse-derived fuel (RDF) for the polygeneration of biofuels along with district heating (DH) and power. A flexible waste gasification polygeneration facility is proposed in this study. Two types of waste—MSW and RDF—are used as feedstock for the polygeneration process. Three different gasifiers—the entrained flow gasifier (EFG), circulating fluidized bed gasifier (CFBG) and dual fluidized bed gasifier (DFBG)—are compared. The polygeneration process is designed to produce DH, power and biofuels (methane, methanol/dimethyl ether, gasoline or diesel and ammonia). Aspen Plus is used for the modelling and simulation of the polygeneration processes. Four cases with different combinations of DH, power and biofuels are assessed. The EFG shows higher energy efficiency when the polygeneration process provides DH alongside power and biofuels, whereas the DFBG and CFBG show higher efficiency when only power and biofuels are produced. RDF waste shows higher efficiency as feedstock than MSW in polygeneration process.

A novel design has been developed to improve the waste-to-energy process through the integration with a biomass-fired power plant. In the proposed scheme, the superheated steam generated by the waste-to-energy boiler is fed into the low-pressure turbine of the biomass power section for power production. Besides, the feedwater from the biomass power section is utilized to warm the combustion air of the waste-to-energy boiler, and the feedwater of the waste-to-energy boiler is offered by the biomass power section. Based on a 35-MW biomass-fired power plant and a 500-t/d waste-to-energy plant, the integrated design was thermodynamically and economically assessed. The results indicate that the net power generated from waste can be enhanced by 0.66 MW due to the proposed solution, and the waste-to-electricity efficiency increases from 20.49% to 22.12%. Moreover, the net present value of the waste-to-energy section is raised by 5.02 million USD, and the dynamic payback period is cut down by 2.81 years. Energy and exergy analyses were conducted to reveal the inherent mechanism of performance enhancement. Besides, a sensitivity investigation was undertaken to examine the performance of the new design under various conditions. The insights gained from this study may be of assistance to the advancement of waste-to-energy technology.

Population growth, urbanization, and changes in lifestyle have led to an increase in waste generation quantities. The waste management system in the Middle East and North Africa (MENA) region is still considered an adolescent system, while developed countries have made great progress in this field, including regulation, financing, administration, separation at source, recycling, and converting waste to energy. At the same time, in the MENA region, the best performance of the recycling process is around 7–10% of total waste. Nowadays, many developed countries like Germany are shifting from waste management to material flow systems, which represent the core of a circular economy. Also, it should be stated here that all countries that have a robust and integrated waste management system include waste-to-energy (W-to-E) incineration plants in their solutions for dealing with residual waste, which is still generated after passing through the entire treatment cycle (hierarchy). Therefore, this paper illustrates the potentiality of embedding waste incineration plants in the MENA region, especially in large cities, and addressing the economic and financial issues for the municipalities. Cities in these countries would like to build and operate waste treatment plants; however, municipalities do not have the sustainable investment and operating costs. The solution is to maximize the income from the output, such as energy, recycling materials, etc. In addition, the MENA region is facing another dilemma, which is water scarcity due to climate change, increasing evaporation, and reduction of precipitation. This research illustrates a simulated model for a waste incineration plant in the MENA region. The EBSILON 13.2 software package was used to achieve this process. Furthermore, the simulated plant applies the concept of waste-to-energy-to-water, so that not only is waste converted to energy but, by efficient usage of multi-stage flash (MSF) technology, this system is able to generate 23 MWe of electric power and 8500 m3/day of potable water. A cost analysis was also implemented to calculate the cost of thermal treatment of each ton of municipal solid waste (MSW) during the life span of the plant. It was found that the average cost of treatment over 30 years would be around US$39/ton.

Biowaste represents a significant fraction of municipal solid waste (MSW). Its separate collection is considered as a useful measure to enhance waste management systems in both the developed and developing world. This paper aims to compare the environmental performance of three market-ready technologies currently used to treat biowaste—biowaste composting, fermentation, and biowaste incineration in waste-to-energy (WtE) plants as a component of residual municipal solid waste (RES). Global warming potential (GWP) was applied as an indicator and burdens related to the operation of facilities and credits obtained through the products were identified. The environmental performance of a WtE plant was investigated in detail using a model, implementing an approach similar to marginal-cost and revenues, which is a concept widely applied in economics. The results show that all of the treatment options offer an environmentally friendly treatment (their net GWP is negative). The environmental performance of a WtE plant is profoundly affected by its mode of its operation, i.e., type of energy exported. The concept producing environmental credits at the highest rate is co-incineration of biowaste in a strictly heat-oriented WtE plant. Anaerobic digestion plants treating biowaste by fermentation produce fewer credits, but approximately twice as more credits as WtE plants with power delivery only.

The assessment of novel waste-to-energy technologies has several drawbacks due to the nature of the R1 formula. The 3T method, which aims to cover this gap, combines thermodynamic parameters in a radar graph and the overall efficiency is calculated from the area of the trapezoid. The present study expands the application of the 3T method in order to make it suitable for utilization in other energy-from-waste technologies. In the framework of this study, a 3T specialized solution is developed for the case of landfilling plus landfill gas recovery, with the potential inclusion of landfill mining. Numerical applications have been performed for waste-to-energy and landfilling by using both the R1 formula and the 3T method. The model Land GEM was used for the calculation of the total landfill gas. The Combined Heat and Power (CHP) efficiency of the landfill gas CHP efficiency was 16.6%–33.1%, and for the waste-to-energy plant, the CHP efficiency was over 70%. The full range of parameters, like metal recovery and quality of CHP, were not fully reflected by the R1 formula, which returned values of 1.07 for waste-to-energy and from 0.37 to 0.63 for different landfilling scenarios. Contrary to that, the 3T method calculated values between 0.091 and 0.307 for the waste-to-energy plant and values between 0.011 and 0.121 for the various landfilling scenarios. The 3T method is able to account for the recovery of materials like metals and assess the quality of the output flows. The 3T method was able to successfully provide a solution for the case of landfilling plus landfill gas recovery, with the potential inclusion of landfill mining, and directly compares the results with the conventional case of waste-to-energy.

Plasma gasification is a thermal treatment successfully applied to waste streams, especially for solid residues. It sets an upgrade to more common waste-to-energy (WtE) techniques as incineration or gasification, granting lower levels of pollutant emissions, less landfilled materials and higher conversion efficiencies and producer gas quality. A life cycle assessment (LCA) of plasma gasification for one ton of a defined stream of solid waste is presented and compared to the hypothetical outcomes of incineration, highlighting the need to implement such sustainable techniques rather than more polluting ones. CML 2001 methodology was applied, enabling the evaluation of eleven impact categories, all of them depicting avoided burdens for the environment. Enhanced efficiency and cleanliness were seen due to the plasma step and to the replacement of part of the electrical grid mix by the produced electricity. Plasma gasification presented an overall better performance than incineration, portraying savings in energy and material resources as well as lower emissions to freshwater. Additionally, lower amounts of air contaminants were seen as well as almost triple of the produced electricity.

The objective of this paper was to provide a preliminary analysis of the utilization of energy derived from waste wood in Taiwan, a highly industrialized country with a high dependence (over 99%) on imported energy. The discussion focuses on the status of waste wood generation and its management over the past decade. Findings show that the quantities of biomass waste collected for reuse purposes in the industrial sectors of Taiwan has exhibited an increasing trend, from about 4000 tons in 2001 to over 52,000 tons in 2010. Although waste wood can be reused as a fuel and raw material for a variety of applications based on regulatory promotion, the most commonly used end use is to directly utilize it as an auxiliary fuel in industrial utilities (e.g., boilers, heaters and furnaces) for the purpose of co-firing with coal/fuel oil. The most progressive measure for promoting biomass-to-power is to introduce the feed-in tariff (FIT) mechanism according to the Renewable Energy Development Act passed in June 2009. The financial support for biomass power generation has been increasing over the years from 0.070 US$/kWh in 2010 to 0.094 US$/kWh in 2012. On the other hand, the environmental regulations in Taiwan regarding the hazard identification of wood-combusted ash (especially in filter fly-ash) and its options for disposal and utilization are further discussed in the paper, suggesting that waste wood impregnated with chromated copper arsenate (CCA) and other copper-based preservatives should be excluded from the wood-to-energy system. Finally, some recommendations for promoting wood-to-energy in the near future of Taiwan are addressed.

The objective of this paper was to provide a preliminary analysis of energy utilization from biological wastewater treatment sludge (biosludge) in Taiwan, a densely populated country (estimate 640 persons/km2) with a high dependence (over 99%) on imported energy. The discussion focused on the status of biosludge generation and its management in the years 2004–2010. Findings showed that the main types of combustible waste (i.e., biosludge) produced by the industrial and agricultural sectors of Taiwan included food processing sludge, wine brewery sludge and agricultural sludge which may be reused as auxiliary fuel in the utilities (e.g., generator, boiler and incinerator). Furthermore, two conceptual biosludge-to-energy systems have been addressed with regard to the thermochemical conversion processes. One is to adopt direct combustion for power generation in the combined heat and power system. Another system uses pyrolysis and gasification for producing biochar (solid fuel), bio-oil (liquid fuel) and syngas (gas fuel). Based on their thermochemical properties and reported generation quantities, the energy potential and the environmental benefits of mitigating CO2 emissions were also analyzed in the study, showing around 1.1 × 103 TJ/year and 57 Gg CO2/year, respectively.