The Agricultural Wastes - Biorefinery Scenario
Based on the discussed above, hypothetic scenarios for the biorefining of agricultural wastes are proposed (Figure 7).
The most profitable use of agricultural residues implies the exploitation of intensive crops (cereals, oil and sugar crops), which have a high yield and require of extensive cultivation areas. The large generation of these wastes ensures the suitable supply of feedstocks for the biorefineries, which can result in high capacity and productive mills. An interesting chance is the integration of food factories and biorefineries, where the residues generated from the processing of crops into primary products, can be biorefined in-situ for the obtaining of other high value sub-products.
But the real challenge in the use of agricultural wastes resides in the integral use of any type of lignocellulosic residues. This subject involves the suitable exploitation of extensive crops, quite delocalized and with lower residue/crop ratios than intensive ones, but that should lead to the socioeconomic development or rural areas.
Obviously, the use of this kind of agricultural residues in high-capacity Biorefineries should not be profitable due to the costly transportation of large amounts of low density residues from local areas to centralized mills. The in-situ processing of these agricultural wastes should also not result economically feasible, because of low capacity processing mills would entail large investments in equipments, manpower and utilities. However, local preprocessing of residues from extensive agriculture into lignocellulosic by-products, and their subsequent transportation to centralized Biorefineries, could be an interesting production chain pathway for the profitable use of these agricultural wastes. In this way, local/rural development could be ensured as well as the proper use of a residue that otherwise would not provide benefits. It should be called ambitious targets for “modest” gains.