Three biomass energy feedstocks (wood, straw, and miscanthus) are co-gasified at 1400 degrees C with two lignites and two hard coals. The objective of this work was to determine the release of alkali metal, chlorine, and sulfur species and to correlate the release with the share of the fuel in the blends. The release of the inorganics is detected using a molecular beam mass spectrometer. Significant species are (H2S+)-H-34, (HCl+)-H-36, (NaCl+)-Na-58, (COS+)-C-60, and (KCl+)-K-74. By comparison of the experimental data with calculations, the influence of the inorganic content of the fuel blends on important release mechanisms and trends is determined. It is shown that the Al/Si ratio and the chlorine content have a major influence on the release of alkali metal species in general. Additionally, it was found that the Al/Si ratio has a strong influence on the release of sulfur species through changes of the availability of Ca.