A process for the manufacture of biodegradable plastic films in aqueous environment, starting from vegetal wastes in powder form includes dissolution at a temperature lower than 50° C. of waste material in form of a powder in an aqueous solution of hydrochloric acid, and transfer of the aqueous solution in a casting mould and evaporation of the aqueous solution, to yield the biodegradable plastic film. The total concentration of the hydrochloric acid is equal to or lower than 5% by weight. The aqueous solution may include acetic acid. The aqueous solution may also be filtered or centrifuged and/or subjected to dialysis against pure water.