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Currently, hydrogen energy is the most promising energy vector, while gasification is one of the major routes for its production. However, gasification suffers from various issues, including slower carbon conversion, poor syngas quality, lower heating value and higher emissions. Multiple factors affect gasification performance, such as the selection of gasifiers, feedstock’s physicochemical properties and operating conditions. In this review, the status of gasification, key gasifier technologies and the effect of solid-fuel (i.e., coal, biomass and MSW) properties on gasification performance are reviewed critically. Based on the current review, the co-gasification of coal, biomass and solid waste, along with a partial utilisation of CO2 as a reactant, are suggested. Furthermore, a technological breakthrough in carbon capture and sequestration is needed to make it industrially viable.

An effective remaining useful life (RUL) estimation method is of great concern in industrial machinery to ensure system reliability and reduce the risk of unexpected failures. Anticipation of an electric motor’s future state can improve the yield of a system and warrant the reuse of the industrial asset. In this paper, we present an effective RUL estimation framework of brushless DC (BLDC) motor using third harmonic analysis and output apparent power monitoring. In this work, the mechanical output of the BLDC motor is monitored through a coupled generator. To emphasize the total power generation, we have analyzed the trend of apparent power, which preserves the characteristics of real power and reactive power in an AC power system. A normalized modal current (NMC) is used to extract the current features from the BLDC motor. Fault characteristics of motor current and generator power are fused using a Kalman filter to estimate the RUL. Degradation patterns for the BLDC motor have been monitored for three different scenarios and for future predictions, an attention layer optimized bidirectional long short-term memory (ABLSTM) neural network model is trained. ABLSTM model’s performance is evaluated based on several metrics and compared with other state-of-the-art deep learning models.

Solid recovered fuel (SRF) residue, which is leftovers from the SRF manufacturing process, usually is discarded in landfill because of its low heating value and high ash and moisture content. However, it could be used as a fuel after mechanical and biological treatment. Gasification experiments were conducted on treated SRF residue (TSRFR) to assess the viability of syngas production. Efforts were also made to improve the gasification performance by adding low-cost natural minerals such as dolomite and lime as bed material, and by blending with biomass waste. In the case of additive mineral tests, dolomite showed better performance compared to lime, and in the case of biomass blends, a 25 wt% pine sawdust blend with TSRFR showed the best performance. Finally, as an appropriate condition, a combined experiment was conducted at an equivalence ratio (ER) of 0.2 using a 25 wt% pine sawdust blend with TSRFR as a feedstock and dolomite as the bed material. The highest dry gas yield (1.81 Nm3/kg), with the highest amount of syngas (56.72 vol%) and highest lower heating value (9.55 MJ/Nm3) was obtained in this condition. Furthermore, the highest cold gas efficiency (48.64%) and carbon conversion rate (98.87%), and the lowest residue yield (11.56%), tar (0.95 g/Nm3), and gas pollutants content was observed.

Proper treatment and careful management of sewage sludge are essential because its disposal can lead to adverse environmental impacts such as public health hazards, as well as air, soil, and water pollution. Several efforts are being made currently not only to safely dispose of sewage sludge but also to utilize it as an energy source. Therefore, in this study, initiatives were taken to valorize sewage sludge cake by reducing the moisture content and increasing the calorific value by applying a hydrothermal treatment technique for efficient energy recovery. The sludge cake treated at 200 °C for 1 h was found to be the optimum condition for hydrothermal carbonization, as, in this condition, the caloric value of the treated sludge increased by 10% and the moisture content removed was 20 wt.%. To recover energy from the hydrothermally treated sludge, a gasification technology was applied at 900 °C. The results showed that the product gas from hydrothermally treated sludge cake had a higher lower heating value (0.98 MJ/Nm3) and higher cold gas efficiency (5.8%). Furthermore, compared with raw sludge cake, less tar was generated during the gasification of hydrothermally treated sludge cake. The removal efficiency was 28.2%. Overall results depict that hydrothermally treated sewage sludge cake could be a good source of energy recovery via the gasification process.

Thirteen types of fuel pellets were prepared from hydrothermally treated hospital solid waste, hydrothermally treated rice straw, pyrolytic plastic waste residue, rice straw, and Sakhalin fir residue using a flat die pellet machine. Different pellet properties such as pellet density, pellet durability, aspect ratio, physicochemical characteristics, and gross calorific value (GCV) were evaluated as well as compared concerning the European standard specification for residential/commercial densified fuels. In addition, the quality of pellets was compared with coal. The results showed that the pellets made only with hydrothermally treated hospital solid waste, hydrothermally treated rice straw, pyrolytic plastic waste residue, and rice straw failed to meet few individual criteria (96.5 wt% pellet durability, and >600 kg/m3 pellet density) of the European standard specifications. However, most of the mixed fuel pellets satisfied the requirement of pellet properties according to the European standard specification. In particular, up to 16.70 wt% hydrothermally treated rice straw, 1.50 wt% hydrothermally treated hospital solid waste, and 4.76 wt% of pyrolytic plastic waste residue can be blended with Shakhalin fir residue to produce low-chlorine fuel pellets. The gross calorific value of pellets made from the mixture of hydrothermally treated wastes and pyrolytic plastic waste residue (around 22 MJ/kg) showed similar results to that of coal. In the case of mixed pellets, the presence of these hydrothermally treated wastes and pyrolytic plastic waste residue valorized the fuel pellet quality. The main outcome of this study was the production of low chlorine biomass fuel pellets of high gross calorific values blended with hydrothermally treated wastes and pyrolytic waste residues, which opens a new door for utilizing waste in a better way, especially hospital solid waste.