## 1 Introduction  
Energy sustainability based on the use of clean and decarbonized energy sources has become a priority and strategic objective for countries around the world. Currently, countries with environmental sensitivity are considering satisfying their current energy demand by applying environmental and energy integration strategies that allow the use of new sustainable energy models based on renewable and more efficient energy. The welfare state of the societies of the future that allow future sustainable economic and social development must be oriented towards preserving the environment and oriented towards sustainability in terms of energy and waste recovery, within the strategies promoted by the EU (European Union) towards circular economy environments [1]. The change in the energy and production paradigm is a reality that implies a change in the energy model, replacing carbonized fossil fuels and oil derivatives with new forms of energy. On the one hand, for the development of a country, high investments are required in relation to the generation of electrical energy. This can be achieved by being more environmentally friendly and seeking more efficient and sustainable forms of clean renewable energy. On the other hand, policies aimed at the recovery and reuse of agricultural, forestry, municipal or industrial waste is a priority framed in the strategies of sustainable recovery and the circular economy [2]. Oil and its derivatives are still considered as the main source of energy, but this situation can be reversed in a short period of time. Researchers of various nationalities are developing new technologies aimed at replacing a reasonable part of fossil fuels with alternative fuels, thus following the new world order that seeks to rethink the ways of obtaining and producing electricity to preserve the environment [3]. Agricultural and forest biomass is a very interesting energy resource due to its high content in (LHV) Low Heating Value and therefore allows its energy conversion through thermochemical processes, such as gasification, with great success and with low environmental impact, contributing to the reduction of the serious problem of global warming [4]. Today, we find material waste of industrial or urban origin with a high potential for recovery or reuse, either as construction materials or in the form of energy. The high specific heat and energy potential makes them perfectly usable as fuel directly or as a raw material for the manufacturing of other fuels [5]. Biomass is a very interesting resource, in some cases with a high calorific power by thermochemical conversion (HLV), and, therefore, it can be converted into different forms of energy that also contribute to the relief of well-known environmental problems associated with global warming [6; 7; 8; 9]. There are high-impact scientific studies that recommend thermochemical recovery as a very appropriate technology for the revaluation of materials through an energy conversion process for the production of syngas [9; 10]. Since the oil crisis of 1973, Refuse-Derived Fuel (RDF) have emerged as possible low-cost replacement fuels. Over the past 10 years, there has been increasing interest in the mining, metallurgical and energy sectors in RDF due to economic and environmental problems. Furthermore, the European energy policy aimed at waste treatment and management has given a new impetus to the use and recovery of non-hazardous waste [11]. These RDF fuels have a biogenic carbon content of around 50-60% and therefore can contribute significantly to reducing CO\({}_{2}\) emissions and increasing the use of renewable energy [12; 13]. On the other hand, plastic waste is, today, one of the most important problems on an urban and industrial scale. To perform energy recovery from plastics, there are two main types of processes to convert waste to energy and fuel: thermochemical and chemical processes [14]. These operations are generally called 'waste-to-energy'.