Abstract: In the present invention, a solution of synthetic anionic surface active agents is at first prepared by mixing and homogenizing sodium polyoxyethylenealkylether sulfate and sodium alpha-olefin sulfonate (both are anionic surface active agents). Distillated water is added to this solution with mixing such that the mixture becomes a mousse-like emulsion that homogeneously contains a sufficient amount of air bubbles. A condensed emulsion fuel material is then produced by adding petroleum liquid fuel to the mousse-like emulsion with mixing. The concentrated emulsion fuel material and an emulsion fuel has an excellent chemical stability and does not separate to water and oil layers even after a long term storage. In addition, as it can be combusted at a high temperature boiler without requiring so much air, the emission of both soot (dust) and NOx are simultaneously reduced.