According to the status report 2013 of Federal Waste Plan 2011 120.000 t of wood and straw ashes were produced in Austria in 2012. Approximately half of the resulting amount of the ash was deposited, whereby all the nutrients, for example all the potassium salts are lost. From the mid-18th to the end of the 19th century potassium carbonate, but also other potassium compounds were extracted from wood ashes by the so-called Ashery-Process. The solvent that was used for the extraction was water, because the potassium salts are easily soluble in water. In the beginning the extraction and evaporation methods were performed archaic. Later they were optimized in factories. Through the revival and modernization of these methods, the easily soluble potassium salts from the ashes, that would get deposited, could be extracted and used as fertilizer. The aims of this thesis are modernization of the extraction technique, to investigate the amount of salts that can be extracted from wood and straw ash of modern combustion plants and an assessment if the extracted salts can be used as a fertilizer later. Therefore attempts have been made, based on historical and modern extraction techniques, to find an ideal multistage extraction method and to reproduce this under laboratory conditions. The resulting extracts were examined for their content of potassium by ion chromatography. Furthermore, heavy metal analysis was made, and the results assessed by comparison with the Austrian Fertilizer Ordinance 2004 and the Austrian Landfill Ordinance 2008. Principally nutritious salts could be extracted, but the yield of salts for the investigated wood ashes was relatively low. The analyzed straw ashes indicated greater yields, and thus a higher potential for economic extraction. The heavy metal contamination of all of the extracted salt was very low so they can be used for fertilizer production.