Enhancement of methane production from various microalgae cultures via novel ozonation pretreatment

In this work, the application of ozone, an unexplored pretreatment to improve methane production from three mixed microalgae sources was investigated. Ozonation at various, culture-dependent dosages was employed and its impact on the efficiency of subsequent anaerobic digestion was examined in comparison with untreated biomass. Regardless of the O-3 pretreatment conditions, the methane yield in all cases could be increased by various extents (6-66%). The highest methane production (432.7 mL CH4 g(-1) VSalgal, equaling to 259.6 mL CH4 g(-1)COD(in)) was attained with the culture composed of 35% Scenedesmus, 30% Dictyosphaerium, 15% Keratococcus, 10% Oscillatoria, 8% Monoraphidium and 2% Nitzchia, using the highest dosage of ozone (382 mg O-3 g(-1) VSalgal) for pretreatment. Electron microscopic assessment revealed the devastating effect of O-3 on algal cell wall structure and integrity, which was thus identified as the key-contributor to the improvement of CH4 fermentation. (C) 2016 Elsevier B.V. All rights reserved.