Saccharina latissima is a carbohydrate-rich fast-growing seaweed (SW) which may be utilized as a marine energy crop. In this study, S. latissima was anaerobically digested for biogas production, and the effects of thermal pretreatment and codigestion with wheat straw (WS) were investigated. Batch experiments showed that pretreatment of SW increased the methane yield from 223 to 268 mL g-1 VS. Codigestion of SW and steam-exploded WS had a clear positive effect on biogas production, giving yields that were considerably higher than what would be expected on the basis of the yields obtained with either of the individual feedstocks. Thus, anaerobic digestion of blends of SW and lignocellulosic substrates provides a promising strategy for biogas production. Although thermal pretreatment increased the yield of biogas from SW such a harsh pretreatment is probably more relevant for the more recalcitrant lignocellulosic substrates.