To balance a fragmented logistics organization, Small and Medium Enterprises have to find collective solutions to decrease their environmental impact. Especially when the demand at each producer takes the form of small packages and low quantities this paper examines the effect of the introduction of a consolidation center on the environmental issue. Therefore, the Fleet Size and Mix Vehicle Routing Problem (FSMVRP) was adapted in order to minimize CO2 emission. An exact mathematical formulation of the extended problem was developed to investigate the difference between homogeneous and heterogeneous fleet size on the environmental issue. Computational experiments for the problem formulation are performed using CPLEX and give a solution of a small instance to illustrate the problem. A case study focuses on optimal parcel picking up, from many producers to a common depot in the agri-food sector.