For the first 20 days (OLR=1.17kgCODm−3 d−1) methane yield is 246 mLCH4 (gCODremoved)−1, then methane yield increased with the removal efficiencies of COD and the stabilization of the reactor, with 416 and 428 mLCH4 (gCODremoved)−1 for OLR =1.75 and 3.5 kgCODm−3 day−1, respectively.