A sebacic acid by-product fatty acid polyester polyol for a polyurethane controlled-release fertilizer envelope, comprising a polyester polyol synthesized by an esterification catalyzed reaction with a sebacic acid by-product fatty acid as a raw material;
- wherein the sebacic acid by-product fatty acid is refined from a by-product produced during preparing a sebacic acid from a castor oil;
- the sebacic acid by-product fatty acid comprises, in weight percentage:
- a palmitic acid 15-25%, a stearic acid 10-16%, an oleic acid 45-57%, and a linoleic acid 12-28%.