The COVID-19 pandemic generated a global upsurge in hospital plastic waste (HPW) as a consequence of the widespread utilization of personal protective equipment (PPE) composed of diverse polymer materials. The constant demand for PPE worldwide led to the accumulation of substantial volumes of high-polymer-based plastic waste. To tackle this challenge, researchers delved into the conversion of HPW into valuable chemicals through a process known as microwave-assisted pyrolysis (MAP). This method entails the transformation of HPW into high-quality char and liquid oil, which can serve as a source of fuel. In this study, our primary focus was to understand how the ratio of HPW (hospital plastic waste) to susceptor weight influenced the yields and characteristics of the resulting products in the context of the MAP process. To facilitate the experimental setup, a Central Composite Design (CCD) was employed. The impact of varying HPW weights and susceptor quantities on the production of value-added products was investigated. The analysis of condensed organic vapor decomposition revealed an increase in liquid yields (73.6 wt %, 76.6 wt %, 80.7 wt %) as the graphite content increased at a constant 30 g HPW. Conversely, gas yield decreased with higher susceptor and HPW quantity. Keeping the graphite constant at 4g, the gas yield declined (32.5 wt %, 30.7 wt %, and 24.7 wt %) as HPW increased. Additionally, gas yield exhibited a drop (32.5 wt % to 18.1 wt %) with an increase in both graphite and HPW. Furthermore, the residual yield decreased (from 1.7 wt % to 1.2 wt %) with a 30 g increase in HPW. In-depth analysis incorporated machine learning techniques to understand the behavior of response variables about susceptor and HPW quantities. The optimization of the MAP process for HPW encompassed various supplementary operational parameters, including susceptor thermal energy, average heating rate, microwave energy, specific microwave power, and product yields. Moreover, the residue generated from the MAP of HPW underwent characterization through X-ray diffraction (XRD), FTIR, and BET analysis.

Lignocellulosic biomass is a promising renewable energy source that can help reduce reliance on fossil fuels. However, its raw form presents challenges for practical use. To overcome this, the Microwave-assisted torrefaction (MAT) process has emerged as a successful method for enhancing the quality of biomass and generating energy. This article aims to provide a comprehensive review of recent scientific research on MAT of biomass. It explores torrefaction indices and discusses the impact of key parameters such as biomass composition, temperature, residence time, heating rate, particle size, and microwave power on MAT. The article also addresses potential applications and challenges associated with MAT. Furthermore, it evaluates the hurdles in achieving compatibility, acceptability, and sustainability of the process, along with future directions to realize economic benefits even in small-scale applications. Ultimately, MAT holds promise as an energy-efficient approach to enhance the effectiveness of biomass utilization.

This study focuses on copyrolyzing pretreated sawdust and polystyrene utilizing microwave-assisted pyrolysis (MAP) with equal mixing to synthesize and characterize biochar. Graphite was used as a susceptor to facilitate precise pyrolysis temperature control. Potassium hydroxide (KOH) powder serves as a catalyst, influencing the char yields and properties. Torrefied raw sawdust at various temperatures (125–175 °C) enhances biochar yields (24–29 wt %). The feedstocks sawdust and polystyrene are characterized by elemental, proximate, and TGA examinations. Furthermore, comprehensive surface, crystallographic, FTIR, and SEM-EDX analyses are performed on microwave copyrolyzed biochar. The developments in BET surface area during copyrolysis show changes concerning pretreatment temperatures: 125 °C (5.6 m2/g) < 150 °C (6.8 m2/g) < 175 °C (8.6 m2/g). Functional groups connected to the alcohols’ O–H bend and C–O stretching vibrations are detected in the biochar samples through FTIR analysis. Sharp peaks with 2θ values between 33.2° and 36.2° appear in the XRD scan of biochar, indicating the presence of crystalline components in the sample. The EDX results demonstrated that the components of biochar included Mg, C, O, and Ca, indicating that it could have plenty of advantageous applications. The study highlights the obstruction of sawdust char’s porous structures by polystyrene, hindering volatile emissions and leading to increased heating rates. These findings underscore the unique contributions of this method to biochar production.