NOVELTY - A dispersion liquid containing algae in a concentration of 5000-1x 1050000 cells/mL is sprinkled on coal pile in a coal yard, to prevent spontaneous ignition and dust generation.    USE - Prevention of spontaneous ignition and dust generation of coal pile used for composite coal fuel, in coal yards (claimed) of thermal power stations.    ADVANTAGE - The method suppresses flow of air to a coal pile during transfer process, by adhering algae on the surface of coal. Quality degradation is prevented. Since algae have high lipid content, the carbon content is high and the heat amount is 80% or more. Hence, mixed combustion property with coal as fuel is improved. Due to the mixed combustion property, carbon neutral can be achieved by a mixed fuel burning ratio, carbon dioxide is reduced, and resources are saved. Since water content (65%) of algae is high, temperature-increase of coal is prevented. Since they are excellent in cooling effect and adhesiveness with lipophilic coal, the algae adhere to the surface of coal and prevent oxidation. The composite fuel has excellent handleability. Even if algae previously dispersed in the dispersion liquid spread on top of the coal pile peel from the surface of coal, a lot of algae exist also in the middle peripheral area by adhesiveness and viscosity of algae. The algae also reduce absorbed heat of coal. Since the length and width of algae are small and algae permeate and reach the pores of lipophilic coal, oxygen diffusion inside coal is interrupted. Industrial water and recycled water of coal yard wastewater can be used as dispersion liquid. During sprinkling, biomass fuel can be automatically mixed with coal. The algae have excellent acid resistance. By utilizing unicellular algae, asexual reproduction is possible and culture medium in power station, factory, etc. can also be propagated easily.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for composite coal fuel comprising aggregated-form coal to which algae is adhered.