This paper aims to briefly overview gasification technologies of biomass and heterogeneous wastes as a means for syngas production. For this purpose, an overview of the existing technologies, their main advantages, limitations, and costs, as well as commercial plants and projects (lower TRL) operating with these technologies and syngas applications is presented. The type of technology and operating parameters should be selected considering the quality of the syngas as it will dictate its end use. Syngas quality is determined by the combination of feedstock properties, type of technology and process operating conditions, and the scale of operation. For smaller projects with a capacity of up to 10 MWth, fixed-bed technologies have been a recurring choice, while fluidized bed reactors can have an installed capacity above 100 MWth and are, therefore, more suitable for medium- and large-scale projects. Fluidized bed gasification technology supports feedstock flexibility, has scale-up potential, and presents relatively low cost, making it a suitable solution and a frequent choice for heterogeneous waste gasification in medium- or large-scale projects. Commercializing waste gasification technology is already a reality. However, more efforts need to be made so that pilot and demonstration projects can overcome the technological and economic problems and move towards commercialization.

Hydrogen is a versatile energy vector for a plethora of applications; nevertheless, its production from waste/residues is often overlooked. Gasification and subsequent conversion of the raw synthesis gas to hydrogen are an attractive alternative to produce renewable hydrogen. In this paper, recent developments in R&D on waste gasification (municipal solid waste, tires, plastic waste) are summarised, and an overview about suitable gasification processes is given. A literature survey indicated that a broad span of hydrogen relates to productivity depending on the feedstock, ranging from 15 to 300 g H₂/kg of feedstock. Suitable gas treatment (upgrading and separation) is also covered, presenting both direct and indirect (chemical looping) concepts. Hydrogen production via gasification offers a high productivity potential. However, regulations, like frame conditions or subsidies, are necessary to bring the technology into the market.

A large part of municipal solid waste (MSW) still goes to landfills, representing an environmental concern. A circular economy approach can enable safe management of MSW while mitigating the increasing energy needs when waste is used as a feedstock in energy production processes (waste to energy). Currently, MSW can be converted into refuse-derived fuel (RDF) through mechanical and biological treatment processes. This study analyzes the status of MSW and RDF production, as well as its main destinations in Portugal and Europe. The legislation applied, possible energy-recovery routes, and challenges associated with energy recovery are discussed throughout this paper. This research finds that the production of RDF in Portugal has been neglected, mostly because of RDF composition being quite heterogeneous and its poor fuel properties. Therefore, the need to improve and upgrade the characteristics and properties of RDF for waste-to-energy processes was detected. RDF can be pretreated to be further applied to waste-to-energy and waste-to-gas processes, such as incineration and gasification. The technology readiness level data, costs, and SWOT analysis allowedto assess that although incineration is the most mature and widely used technology, gasification becomes more attractive, having lower costs and gaseous emissions, proving to be more efficient and sustainable for MSW and RDF conversion.

The production of heterogeneous solid waste, such as municipal solid waste (MSW), construction and demolition waste (CDW), and industrial solid waste (ISW), has increased dramatically in recent decades, and its management is one of today’s biggest concerns. Using waste as a resource to produce value-added materials such as char is one of the most promising strategies for successful and sustainable waste management. Virtually any type of waste, through various thermochemical technologies, including torrefaction, pyrolysis, hydrothermal carbonization, and gasification, can produce char with potential material and energy applications. Pyrolysis is the most widespread technology, and there are more studies on producing and applying waste-derived char using this technology. The properties of waste-derived char seem to be influenced by the conversion technology and conditions, as well as by the composition of the source waste. A literature search indicated that the properties of waste-derived char are highly variable with the composition of the raw material, with carbon content in the range 8–77%, a higher heating value of 2.5–28.4 MJ/kg and a specific surface area of 0.7–12 m²/g. Depending on the properties of char derived from waste, there are greater or minor difficulties in applying it, with ash content, heavy metals, and polycyclic aromatic hydrocarbon (PAH) concentrations being some of its limiting properties. Therefore, this review attempts to compile relevant knowledge on the production of waste-derived char, focusing on heterogeneous solid waste, applied technologies, and practical application routes in the real world to create a supply chain, marketing, and use of waste-derived char. Some challenges and prospects for waste-derived char are also highlighted in this study.

Mobile pyrolysis systems offer a practical pathway for the decentralized valorization of biomass waste, addressing the high logistical and economic burdens of transporting low-density, moisture-rich feedstocks to centralized facilities. By operating directly at the source, these systems convert diverse agricultural and forestry residues into biochar, bio-oil, pyrogas, and wood vinegar, while reducing transport volumes and associated emissions. Reported mobile reactors process between 4 kg per batch and 10 t/day, achieving biochar yields of 33–44 wt.% at 400 °C and bio-oil yields of 55–68 wt.% in fast pyrolysis at 500–550 °C, demonstrating performance comparable to stationary installations. This review synthesizes current mobile pyrolysis technologies, including reactor configurations, feedstock suitability, operational constraints, and recent advances in automation, real-time monitoring, and machine learning-based optimization. The agricultural and industrial applications of pyrolysis products are examined, with emphasis on soil health enhancement, biopesticide activity, renewable gas generation, and carbon sequestration. Emerging international projects and commercial efforts are highlighted, illustrating growing interest in flexible, low-carbon pyrolysis solutions for rural waste management and distributed bioresource utilization, while outlining the technological gaps that remain to be addressed.