1. Introduction2. Part I. Waste ash: characterization and uses2.1. Types of ash and characterization2.1.1. Coal ash2.1.2. Biomass ash2.2. Effects of combustion processes on ash composition and properties2.3. Diffuse fly ash utilization2.3.1. Environmental uses of fly ash2.3.2. Construction industry2.3.3. Ceramic industry2.3.4. Catalysis3. Part II. Overview of zeolite synthesis from ash3.1. Synthesis processes3.1.1. The hydrothermal process3.1.2. The alkaline fusion-assisted hydrothermal process3.1.3. The multi-step treatment method3.1.4. Microwave irradiation3.1.5. The sonication approach3.2. End uses of synthetic zeolites3.2.1. Environmental pollution3.2.2. Catalysis3.2.3. Emerging applications and nanozeolite4. ConclusionsReferences