Prospects for commercial microalgal biorefineries: Integrated pilot demonstrations and process simulations based techno-economic assessment of single and multi-product value chains

Abstract

Pilot-scale demonstrations and techno-economic simulations are proposed for overcoming uncertainties surrounding technology scale-up impacts and economics of microalgae (MA) biorefineries. Therefore, to contribute to knowledge on promising value chains regarding near-term commercialization, this study investigated the techno-economic performances of alternate commercial (1–10 t MA/d) spirulina MA biorefinery scenarios via integrated pilot demonstrations and Aspen Plus® process simulations. The scenarios include spirulina cultivation and processing into: (I) dried spirulina food product (DSFP), (II) phycocyanin (PCN), (III) PCN + biostimulant for plants (BFP), (IV) 50:50 % MA feedstock split for DSFP and PCN + BFP, and (V) similar to IV but integrated with cattle-dung biogas heat system (CDBHS) allowing for additional liquid biofertilizer recovery. DSFP prices of 13.2–17.3 €/kg (4-fold to 5-fold lower vs market average) were sufficient for profitability of I. Conversely, II and III were unprofitable per the relatively high PCN prices projected for viable operations (283–544 €/kg PCN vs market prices at 170–280 €/kg PCN). Integration of DSFP into the PCN + BFP (IV) plus CDBHS (V) resulted in economically viable biorefineries. Thus, for near-term commercial applications, the integration of the DSFP into the spirulina biorefineries could be strategic for advancing viable productions of the emerging PCN and BFP products. Optimization opportunities for the MA cultivation (e.g. achieved productivity of 8.6 g/m2.d vs reports of 14 g/m2.d) and the downstream processing (e.g. attained PCN yield of 6 % vs theoretical 11 %) could be explored to improve the biorefinery cost and revenues [e.g. 11 % PCN yield corresponds to comparable PCN prices vs the market, i.e. 250–296 €/kg (II) and 154–193 €/kg (III)]. Hence, although the multi-product biorefinery schemes (III-V) could improve the bioresource utilization efficiency, their near-term economic viability will depend largely on the values of the products and technology efficiencies rather than the number of products recovered.