The invention pertains to a process for producing a glycerol tri-carboxylic acid polyester foam which comprises the steps of combining glycerol and a tri-carboxylic acid in the liquid phase to provide a reaction mixture, and keeping the reaction mixture at a temperature of between 80° C. and 130° C. from the start of the reaction until a conversion of at least 90% is obtained.The foamed polyester of the present invention is “green”, biodegradable, and non-toxic, and can be cleanly combusted. It finds application in, int. al., packaging materials, insulation materials, and materials with a short life cycle.