Abstract: Thermal treated coal which has a water content of not more than 10%, which has pores with an oil adsorbed onto and impregnated into the pore surface, and which is decarboxylated and dehydrated to have a reduced porosity is provided. In its manufacture, porous coal and an oil are mixed to prepare a slurry, and the slurry is heated for effecting slurry dewatering. During the slurry dewatering, oil is adsorbed onto the surface of the pores of the porous coal. Subsequently, the slurry is heated for refining, followed by a solid-liquid separation at the final stage.

Abstract: A biodegradable plastic added at an amount of a hydrophilic property imparting-substance providing wettability such that the contact angle of plastic surface to water is 70.degree. or less whereby the decomposability thereof with Basidiomycetes, the cultured products thereof and/or the processed products thereof is improved. A method for decomposing plastic under the conditions with limitation to nitrogen and/or carbon in decomposing such biodegradable plastic. In accordance with the present invention, the plastic which has conventionally been decomposed with difficulty can be decomposed efficiently.