Abstract: Environmental regulations tend to restrict the emissions from pulping platns, which increase the amount of sulphur and chlorine in the cooking liquor to undesirable amounts. This is detrimental to the process and increases the risk of corrosion upon the furnace walls. According to the invention certain metals, preferably iron and/or aluminum are burned together with the waste liquor, and will form compounds with the sulphur and the chlorine, respectively, which are easily separated from the chemicals taking part in the normal process cycle.