The Challenge of the Agricultural Wastes Biorefining
Benefits and Drawbacks of Agricultural Wastes as Biorefinery Feedstock
So far, the benefits from the use of agricultural residues for the production of value-added products result evident (Figure 6). First of all, the sustainable and renewable nature of these feedstocks implies an environmental advantage against the use of other natural resources.
Agricultural activities are worldwide widespread, so the development of local economies based on this valueless feedstock could represent a clear positive milestone. Much of the rural population is employed directly in agriculture, as smallholders or farm labourers. Their income can be strengthened by exploiting this type of waste, improving access to services, including education and health, from less developed areas.
However there are some economic drawbacks related to the development of biorefineries of agricultural wastes. Even though this feedstock is worldwide available, the periodicity or seasonality in the harvesting of most crops could lead to their batch-processing into marketable products. This is the reason why nowadays only high capacity centralized mills for the processing of highly yielding crops are being projected (based on intensive crops such as cereals, oil palm or sugarcane). Also the physicochemical properties of the agricultural residues (heterogeneous composition and low density) seem to set aside the utopia of the processing of different wastes from various crops and from delocalized farms. Solving of the last drawback should lead to larger investments, not only for management and transportation of the agricultural residues to the processing mills, but for the equipments and technology required for their suitable transformation.
Figure 6. Pros and cons of the use of agricultural wastes in Biorefineries.
Figure 7. Biorefinery scenarios for intensive and extensive crops.