Several wastes from agro-industrial activities were mixed in different ratios to evaluate the co-digestion process. Methane yield (Y(CH4)), specific methanogenic activity (SMA) and a kinetic parameter (k(0)) were determined. A second feeding was also performed to examine the recovery of bacterial activity after exhaustion. Mixture ratios of 1:1:1:1 and 1:3:4:0.5 (w/w) showed the best performance, with Y(CH4) of 664; 582 NmL CH(4)/gVS(substrate), as well as SMA of 0.12: 0.13 gCOD(NmLCH4)/gVS(inoculum)/d, respectively, during the digestion of the first feed. It was possible to relate synergetic effects with enhancement in Y(CH4) by up to 43%, compared with values calculated from Y(CH4) of the individual substrates. All batches started up the biogas production after an exhaustion period, when a second feed was added. However, long lag phases (up to 21 days) were observed due to stressed conditions caused by the substrate limitation prior to the second feed. (C) 2011 Elsevier Ltd. All rights reserved.