Assessment of Agroforestry Residues: Their Potential within the Biorefinery Context

The concept of bioeconomy has been promoted worldwide in order to replace fossil-based resources and to find new strategies for waste management, by converting biomass into energy, chemicals, and value-added products, in a sustainable way. Despite the efforts that have been made in this area, there are still some unexplored raw materials globally, namely from agricultural and forestry industries. Therefore, the aim of this work was to characterize four abundant residues from the Portuguese agroforestry industry, including pruning residues (pine branches, PB) and stumps (PS), tomato waste (TW), and winery wastewater (WW), for analyzing their potential within the biorefinery context. Volatiles were analyzed by gas-chromatography, and compounds with repellent/attractant properties were found for PB and PS, while flavor-enhancers were particularly identified in agrowastes. Composition analysis revealed that both TW and WW had the potential for biogas generation (BMP ∼340 and ∼250 NL CH4/kg VS, respectively), whereas forestry residues (PS and PB) can be recovered for thermal energy (HHV ∼20 MJ/kg) and bioethanol production (∼0.3–0.4 L/kg). Among all the aqueous extracts that were obtained, PS showed both the highest antioxidant activity (IC50 ∼6 μg/mL) and total phenolic content (∼400 mg GAE/g extract). All residues were demonstrated to be promising for the Portuguese biobased economy.