Ensiling of sugar kelp biomass for biorefining

Seaweeds are generally harvested at certain seasons to obtain optimal yield and quality for specific purposes. Year-round biorefining of seaweed, therefore, requires storage of the biomass from harvest to processing. We investigated ensiling as a method for preserving seaweed biomass for subsequent biorefinery. In lab-scale and pilot-scale experiments of up to one-year duration, sugar kelp (Saccharina latissima) biomass was preserved by either biological ensiling by means of lactic acid bacteria (LAB) fermentation or by chemical ensiling by addition of lactic acid to reduce pH. The results clearly demonstrated that the ensilability of sugar kelp was positively correlated with the glucose content of the biomass. The ensiling process could be optimized by application of molasses and further improved by addition of LAB inoculum. The doses of molasses and lactic acid were important for pH after biological and chemical ensiling, respectively. Biological ensiling reduced the content of glucose and increased the content of fermentation products. In conclusion, ensiling appears to be an interesting preservation method for seaweed biomass, which may be optimized by application of ensiling additives. However, ensiling also changes the chemical composition of the biomass, and the applicability of ensiling for preserving seaweed biomass may depend on the subsequent use of the silage in biorefinery processes.