A masterbatch is disclosed, along with associated methods, and biodegradable filaments, fibers, yarns and fabrics. The masterbatch includes 0.2 to 5 mass % CaCO3, an aliphatic polyester with a repeat unit having from two to six carbons in the chain between ester groups, with the proviso that the 2 to 6 carbons in the chain do not include side chain carbons, and a carrier polymer selected from the group consisting of PET, nylon, other thermoplastic polymers, and combinations thereof.