Enhancement of microalgae anaerobic digestion by thermo-alkaline pretreatment with lime (CaO)

The aim of this study was to evaluate for the first time the effect of a thermo-alkaline pretreatment with lime (CaO) on microalgae anaerobic digestion. The pretreatment was carried out by adding different CaO doses (4 and 10%) at different temperatures (room temperature (25 degrees C), 55 and 72 degrees C). The exposure time was 4 days for pretreatments at 25 degrees C, and 24 h for pretreatments at 55 and 72 degrees C. Following, a biochemicalmethane potential test was conducted with pretreated and untreated microalgae. According to the results, the pretreatment enhanced proteins solubilisation by 32.4% and carbohydrates solubilisation by 31.4% with the highest lime dose and temperature (10% CaO and 72 degrees C). Furthermore, anaerobic digestion kinetics were improved in all cases (from 0.08 to 0.14 day(-1) for untreated and pretreated microalgae, respectively). The maximum biochemical methane potential increase (25%) was achieved with 10% CaO at 72 degrees C, in accordance with the highest biomass solubilisation. Thus, lime pretreatment appears as a potential strategy to improve microalgae anaerobic digestion. (C) 2017 Elsevier B.V. All rights reserved.