Optimisation of biogas production from the macroalgae Laminaria sp. at different periods of harvesting in Ireland

Brown seaweeds are a suitable substrate for biogas production through anaerobic digestion (AD). Since the carbohydrates’ content is subjected to a seasonal variation, this research aimed to select the best harvesting period of beach cast brown seaweed Laminaria sp. for methane production, while optimising the use of a beating pretreatment and the organic substrate concentration. Response surface methodology (RSM) was used to estimate the effect of the beating pretreatment in terms of pretreatment time (5–10–15 min) and organic matter concentration in terms of volatile solids (VS) (1–2.5–4%) on methane production. The highest methane yield of 342 ± 17 ml g^-1 VS was observed during November at 1% of VS and after 5 min of pretreatment, while the lowest yields were registered in March with an average of 163 ± 28 ml g^-1 VS. However, an enhancement of 47% with respect to the untreated sample was achieved at 2.5% of VS and after 15 min of pretreatment, in March.