Spruce wood (50 wt.%) and copy paper (50 wt.%) were mixed to mimic the biomass content in RDF, whereas polyethylene (PE, 74 wt.%), polyvinyl chloride (PVC, 20 wt.%) and polyethylene terephthalate (PET, 6 wt.%) were mixed to mimic the fossil fraction of RDF (all weight fractions in DAF basis). Prior to mixing, the pure materials were separately ground into