“…The composition yields and characteristics of the gasification products depend on the composition and structure of the biomass, process conditions (such as temperature, gasification agent, pressure, residence time or use of catalyst) and reactor type [49]. Even small changes in process conditions could affect the overall performance of the gasification process, and therefore the quality of the final product gas [50]. Thus, clean woody biomass leads to a product gas with very low concentrations of NH 3 , H 2 S and HCl, as it contains low amounts of sulphur, nitrogen and chlorine compounds, whereas the use of low-cost residual biomass, such as agricultural residues, manure [51], sewage sludge [52] or waste [53], leads to much higher concentrations.…”