The Storage and Production of Bioenergy Using Macroalgae Biomass—Part I: Ensiling

Ensiling is a promising low-cost preservation approach that allows for a year-round supply of kelp feedstock for biofuel production via anaerobic digestion. In this study, farm-grown kelps of known age were ensiled with and without the addition of lactic acid bacterial (LAB) inoculant for a duration of up to one year in order to test long-term storage suitability. The study looked at the impacts of different bacterial inoculums on the chemical and microbial composition over the duration of storage. Significant fluctuations in the pH were observed during ensiling, leading to some cases of secondary fermentation and a loss of volatile components; however, over 12 months, the total mass loss was <2% on average. Biochemical compositional changes occurred in the silage over a period of 12 months, but protein, lipid and carbohydrate content remained suitable for biogas production. Microbial analysis showed variability in the bacterial distribution between the ensiled samples that was coincident with pH variability. Despite this variability, the bacterial communities underwent a succession with a selection for ensilage bacteria and drop in spoilage organisms. This shift supports the viability of this ensiled material for future usage. The impact of ensiling on bioenergy production through anaerobic digestion is explored in the second part of this two-part paper.