# Study of the Applicability of Thermochemical Processes for Solid Recovered Fuel
###### Abstract
SRF is produced from non-hazardous solid waste components, and its composition aligns with the combustion requirements set by national and EU specifications [23], so energy recovery through combustion processes appears as an interesting alternative. Numerous studies have been conducted on the use of the SRF obtained from the non-recyclable part of municipal solid waste as fuel in combustion processes in cement kilns, lime kilns, and waste-to-energy (WtE) plants [24]. Both economic and environmental issues have been analysed, and the results confirm that this alternative could be a viable solution [25]. Currently, the thermal substitution rate of traditional fossil fuels with SRF in this type of combustion process can vary from 40% to 70% [26]. Gasification converts a carbonaceous material into a gaseous fuel by heating it in a gasification medium, typically air, oxygen, steam, or carbon dioxide (and their mixtures). Operating conditions, such as the temperature, the equivalence ratio (ER), and the gasifying agent, play a relevant role in gas composition [27], which defines its quality and potential uses in gas engines and turbines or as a chemical feedstock to produce liquid fuels [28]. The gasification of SRF from different origins, such as MSW [17] and automotive and plastics recycling industries [29], has been reported in the literature. It has also served as feed for co-gasification processes with other input streams such as wood [30], sewage sludge, or paper waste [31]. The influence of temperature and ER has been analysed in several works [32], with a general trend showing that increasing the temperature with a fixed ER implies an increase in the gas yield [33]. LHV of the gasification gas has also been the subject of study for energetic purposes [34], but unanimity on the effect of the operational parameters has not been reported; therefore, as concluded [35], LHV of the gas seems to be highly dependent on the composition of SRF. To the best of our knowledge, there is a gap in the literature regarding the energy recovery from screening waste from WWTPs. This study builds on the successful production of SRF from this waste, in pelletised forms [14], and presents a theoretical energetic assessment (based on enthalpy balances) of two thermochemical routes, combustion and gasification, which are potential treatments for energy recovery from SRF derived from screening waste. In addition, since information about the gasification of SRF from screening waste is scarce in the literature, the present work also provides some experimental data (product yields, syngas composition, lower heating value, and tar content) obtained in the gasification of this type of waste with air and air/steam as gasification medium. These experimental data have been used for energetic calculations in the gasification process. Complete combustion was considered in the energetic assessment of the SRF from screening waste combustion, avoiding the need for experimental data in this calculation. The findings of this study will provide a first approach to more sustainable management alternatives for this waste, involving energy recovery as opposed to the current practice of disposing of screening waste in landfills.