All fuels except WP were collected from a recycling centre and waste treatment plant sited in southern Sweden and owned by VafabMiljö AB. For each individual fuel, a standardized quartering procedure was performed to ensure a 25 kg representative sample of each type. Since the amount of sample used in the tests was very low, it was important to perform thorough grinding and homogenization to ensure representative and homogenous samples for analysis. Prior to analysis, samples were air dried and metal and glass pieces were removed manually from the waste materials and RW. Next, samples were homogenized, ground using a Retsch SM 200 cutting mill and sieved to ⩽1 mm and homogenized again. Finally, materials were ground again and sieved to ⩽500 μm and further homogenized prior to analysis (see Figs. S1–S3 available in supplementary material about FF and EFF production and sampling and sample preparation respectively).