Impact of biochemical composition on susceptibility of algal biomass to acid-catalyzed pretreatment for sugar and lipid recovery

One of the major challenges associated with algal biofuels production in a biorefinery-type setting is improving biomass utilization in its entirety, increasing the process energetic yields and providing economically viable and scalable co-product concepts. We focus on the impact of compositional characteristics of biomass on the susceptibility to pretreatment in order to maximize the valorization of algal biomass conversion for biofuels and bioproducts. The release of monomeric carbohydrates in the aqueous phase and extractability of the lipid fraction was measured based a response surface methodology to find significant explanatory variables and interaction terms. We studied the effect of harvest timing on the conversion yields, using three algal strains; Chlorella vulgaris and Scenedesmus acutus and Nannochloropsis granulata representing three different nutritional metabolic phases. Four cultivation conditions of high (≥90 gallon gasoline equivalent/ton biomass) value for a combined sugar- and lipid-based biofuels process were identified. These four conditions represent either mid or late stage harvest cultivation regimes. The results indicate that acid pretreatment has potential to be applicable for a vast range of biomass samples to obtain high energy yields, but that the exact conditions and optima are dependent on the strain and likely the starting composition of the biomass.