2.2.1.2. Second objective: minimization of the weighted unused waste biomass. The second objective function minimizes the total waste biomass amount that is not collected from the biomass source sites. Different from the previous research, each supply regions have been assigned a weight reflecting the urgency of waste disposal in the site. The following equation shows the calculation of the second objective function:
Weighted unused waste biomass amount
2.2.2. The constraints 2.2.2.1. Biomass supply constraints. Eqs. (12) and (13) present con-
straints that ensure the biomass procurement amount from a supply region must not exceed the total available biomass in that region. Seasonal availability of feedstock is also considered. Size of the land leased for energy crop cultivation is equivalent to proportion of the total out of use agricultural land in the biomass source site.
2.2.2.2. Flow conservation constraints. Flow conservation constraints are imposed on the bioenergy plant site and inventory site. It is assumed that inventory turnover is only allowed for energy crops due to natural deterioration of animal wastes. Eqs. (14) and (15) represent constraints that ensure the amount of biomass shipped from the biomass source site to the inventory site is equal to the amount of biomass shipped to the bioenergy plant site from the inventory site.