The invention relates to a foam ply based on a biodegradable polyester mixture, comprising i) from 70 to 5% by weight, based on the total weight of components i to ii, of at least one polyester based on aliphatic and aromatic dicarboxylic acids and on aliphatic dihydroxy compounds, and ii) from 30 to 95% by weight, based on the total weight of components i to ii, of poly-lactide, and iii) from 0.1 to 5% by weight, based on the total weight of components i to ii, of a copolymer which comprises epoxy groups and is based on styrene, acrylates, and/or methacrylates, and iv) from 0.5 to 15% by weight of additives; and v) from 0 to 50% by weight of inorganic or organic filler, and also to processes for production of the foam ply mentioned, and to the use of the foam plies for the production of moldings and foils, and also to moldings and foils comprising the foam plies mentioned.