Kingston’s public library is facing the prospect of state decertification because the recently approved town budget falls short of state standards. The budget provides for more than $30,000 in spending on new library materials in the fiscal year that begins July 1. But the state certification standard calls for spending almost three times that amount. If the library loses its certification, it would lose such privileges as participation in the Old Colony Library Network, which allows the Kingston library card holders to borrow materials from other libraries in the network. Kingston has received waivers from the spending standards in previous years because of revenue shortfalls, but town officials said a waiver is unlikely this year because of overall improved finances.