Potassium-type zeolite (K-zeolite) was synthesized from coal fly ash and woody biomass incineration ash by microwave hydrothermal treatment. The woody biomass incineration ash was discharged from a biomass power plant, and extracted solutions of the material had a pH range of 11.5-13.0 and a high potassium concentration; therefore, it could be employed to replace the KOH solution that is typically used in the synthesis of K-zeolites. Consequently, we successfully synthesized a K-zeolite containing phillipsite phases from coal fly ash using extracted solutions obtained from biomass incineration fly ash. The ammonium adsorption capacity of the K-zeolite synthesized by microwave hydrothermal treatment was comparable to that of K-zeolite synthesized by oil-bath hydrothermal treatment (external heating). We also confirmed that the microwave heating method could shorten the K-zeolite synthesis time compared to that required when using oil-bath heating. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.