The invention provides novel polyesters, fibers and films, nonwovens from the fibers and disposable products of the polyesters such as diapers. The products are degradable under the conditions typically existing in waste composting processes, have low ingredient costs and yet provide strength and toughness properties adequate for end uses such as in disposable diapers. The polyesters are based upon polyethylene terephthalate copolymerized with a non-aromatic diacid, such as adipic and glutaric acids, and containing alkali metal or alkaline earth metal sulfo groups, such as a metal 5-sulfoisophthalic acid derivative.