The objective of this study was to evaluate the effect of beating (BT), ball milling (BM) and microwave pretreatment (MW) on the conversion of the macroalgae Laminaria spp. into biogas by anaerobic digestion (AD). The AD was carried out in batch at 38 +/- 1 degrees C, over an incubation time of 25 days. After 3 days of digestion the BT pretreated samples yielded the best result by achieving a methane increase of up to 37% with respect to the raw seaweed. At 25 days, both BM and MW pretreatment lowered the methane yield with respect to the raw seaweed. Since BT produced higher methane yields with respect to the untreated sample, it was considered for energy balance analysis. After 3 days of digestion, the BT resulted in an energy gain of 28%, while at the end of digestion the break-even point was reached. (C) 2015 Elsevier Ltd. All rights reserved.