Equilibrium calculations of the combustion of wheat straw in an excess of air at 1 atm were carried out at temperatures ranging from 500-1200 degrees C. A low melting molten silicate was present at all temperatures which, in addition to a large concentration of silica (76-83 mol%) and potassium (10-12 mol%) contained small concentrations (<5 mol%) of calcium, sodium, magnesium and aluminum oxides as well as small amounts of chloride, sulfate and carbonate. This liquid is the probable cause of problems with fouling and corrosion in combustors using wheat straw. The identification of this liquid is an aid in deducing solutions to these problems. (C) 1997 Elsevier Science Ltd.