Biogas production from the anaerobic digestion of Laminaria digitata in a 10 L pilot-plant with digestate re-use as fertiliser

Seaweed has received considerable interest as a potential feedstock for producing biofuels. The anaerobic digestion (AD) of seaweed is a feasible technology where biogas is produced as a source of renewable energy. The effluent (digestate) is considered a by-product that can be used as bio-fertiliser. This investigation examined the co-digestion of Laminaria digitata with bovine slurry in a batch two-phase AD process. Two 10 L pilot-plants running in parallel were fed with the mixture and incubated at 35°C for 109 days. Two biofuel crops, ryegrass and sunflower, were grown with different concentrations of digestate and the effect on seed germination and plant growth was evaluated. Three hundred and seventy-five millilitre and 217 ml g/VS of biogas and methane, respectively, were produced from the AD. Digestate addition enhanced plant growth.