Forest Incentives Program Act of 2018 This bill directs the Department of Agriculture (USDA) to create certain programs that provide incentives to reduce greenhouse gas emissions. Specifically, USDA must establish an incentives program to achieve supplemental greenhouse gas emission reductions and carbon sequestration on U.S. private forest land (eligible land) through carbon incentives contracts and conservation easement agreements. Under the program, USDA must make payments to owners of eligible land for: (1) certain forestry practices that increase carbon sequestration and storage over a designated period on eligible land, and (2) conservation easements on eligible land. In addition, USDA must establish an incentives program to achieve supplemental greenhouse gas emission reductions from materials in nonresidential buildings used for commercial or state or local government purposes. Under the program, USDA must provide owners of such buildings payments for the use of eligible products for sequestering carbon in those buildings. Eligible products are commercial or industrial products that are composed of biological products, including renewable agricultural and forestry materials.