In this research, biogas production potential from beach wrack collected in Riga Gulf (Ragaciems, Jaunķemeri, Bigauņciems) and in coastline of Sweden (Kalmar) was studied using an anaerobic digestion method. Selected beach wrack masses laying ashore and containing macroalgal biomass of common macroalgae types specific to the Baltic Sea were mixed for consolidated samples. Anoxic fermentation of untreated beach wrack was carried out in 16 bioreactors applying a single filling mode at 38 °C. The study revealed that by utilizing beach wrack accumulated ashore as a feedstock for anaerobic digestion methane can be utilized if pretreatment and conditioning of the samples are performed. The study was continued for selected brown algae containing biomass tested with three dewatering pretreatment methods: a) keeping in tap water for 24 hours; b) washing with running fresh water for one hour, and c) drying to relatively constant weight. The resulting methane outcome was compared with the data corresponding to raw brown algae. The study confirmed that washing of macroalgal biomass applied as pretreatment prior to anaerobic fermentation avoids inhibition of salts and promotes biomethane production.