Multiscale scheme for the optimal use of residues for the production of biogas across Castile and Leon

This work evaluates the exploitation of four different types of waste for the production of biogas and fertilizer using a feedback multiscale analysis approach. The yield of sludge, manure, municipal solid wastes (MSW) and lignocellulosic residues is evaluated and the kinetics of the anaerobic digestion of each of these residues is determined by performing a parameter estimation using experimental data. It turns out that hydrolysis is the limiting stage. Next, a techno-economic evaluation of a processing facility is carried out. Finally a supply network model is developed to evaluate the optimal use of the residues over a region in Spain. The network is formulated as a mixed integer linear programming problem selecting the type of residue, the number and size of the digesters and the location of the plants across 59 shires of a particular region in Spain for the available budget. MSW is the selected waste due to its wide availability and large yield to fertilizer. Lignocellulosic residues are the second best option. Only intrashire transport is suggested. The shires selected for waste processing are rather scattered as a function of the resources available and the already installed facilities. However, the amount of residues available can provide more than three times the region demand for natural gas, but the budget required adds up to more than 4.4 ·109 €