Officials with the University of Maine system said the state’s public universities are launching a program to use local growers and producers for a fifth of their dining hall expenditures by 2020. The approximately 35,000-student system says it expects purchases from local producers to exceed $1.5 million by 2020. The system released a request for proposals to provide dining hall and other food services at six of its seven campuses Monday. The goal for the first year of the contract is 15 percent local food, to be increased by another percentage point annually over the initial five years of the contract. The University of Maine system is defining local food as food harvested or produced within 175 miles of any campus in the system.