High-rate biomethane production from microalgal biomass in a UASB reactor

Biomethane production from the microalga Scenedesmus sp. AMDD was demonstrated in an upflow anaerobic sludge bed (UASB) reactor. A full factorial design experiment was used to identify the effect of organic loading rate (OLR) of algal biomass and hydraulic retention time (HRT) on the volumetric rate of methane production. At an HRT of 4 days and an OLR of 3.23 gTVS L-R(-1) d(-1) corresponding to an influent microalgae concentration of 12 g total volatile solids (TVS) L-1, the volumetric rate of CH4 production reached 0.6 LSTP L(R)(-1)d(-1). A methane yield of 0.18-0.2 L per gTVS of fed microalgae was estimated. A stable performance was observed throughout 3 months of UASB reactor operation. Due to the short HRT and the good performance of UASB reactor, operated at influent microalgae concentrations in a range of 4-12 gTVS L-1, this reactor type is suitable for coupling with photobioreactors equipped with gravitational settlers. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.