Energetic and biochemical valorization of cork boiling wastewater by anaerobic digestion

• Published in: Biotechnology for biofuels Vol. 7; no. 1; p. 67
• Main Authors: Marques, Isabel Paula, Gil, Luís, La Cara, Francesco
• Format: Journal Article
• Language: English
• Published: England Springer-Verlag 24.04.2014; BioMed Central Ltd; BioMed Central
• Subjects: Anaerobic digestion; anaerobiosis; benzoic acid; Biochemistry; Boiling; chemical oxygen demand; Cork; Effluents; electrochemistry; electrolytes; ellagic acid; energy; environmental hazards; enzyme activity; industry; laccase; methane; Toxic; toxicity; Toxicology; ultrafiltration; viscosity; Waste water; wastewater; xylanases; Mediterranean region; Portugal; Methane; Cork boiling wastewater; Phenols; Enzymes; Anaerobic digestion; Valuable biomolecules
• ISSN: 1754-6834; 1754-6834
• DOI: 10.1186/1754-6834-7-67

BACKGROUND: In addition to energy benefits, anaerobic digestion offers other interesting advantages. The cork industry is of great environmental, economic and social significance in the western Mediterranean region, with Portugal being the world-leading producer and exporter. Cork boiling wastewater (CBW) is a toxic and recalcitrant organic effluent produced by this sector, which constitutes a serious environmental hazard. However, there is no documented research on anaerobic treatment/valorization performed with this effluent. The work presented here was developed with the aim to use the anaerobic digestion process to convert the CBW polluting organic load into an energy carrier gas and valuable molecules for industry. RESULTS: No lag phases were observed and a methane yield of 0.126 to 0.142 m³ kg⁻¹ chemical oxygen demand (COD)ₐddₑd was registered in the mesophilic consortium experiments carried out in batch flasks at 37 ± 1°C. Anaerobic digestion can be advantageously connected to ultrafiltration or electrochemical processes, due to the following: 1) reduction of ellagic acid content and consequent decrease of CBW viscosity; and 2) increase in conductivity after the anaerobic process, avoiding the electrolyte application of the electrochemical process. The improvement of several CBW biochemical features shows that anaerobic digestion may provide additionally useful molecules. The rise in concentration of some of these compounds, belonging to the benzoic acid family (gallic, protocatechuic, vanillic and syringic acids), is responsible for the increase of antiradical activity of the phenolic fraction. Additionally, some enzymatic activity was also observed and while the laccase activity increased in the digested effluent by anaerobiosis, xylanase was formed in the process. CONCLUSIONS: The multidisciplinary approach adopted allowed the valorization of CBW in terms of energy and valuable biomolecules. By exploiting the anaerobic digestion process potential, a novel methodology to toxic and recalcitrant cork processing wastewater was developed.