Economic and environmental analysis of algal biorefinery for the production of renewable fuels and co-product

Abstract

• Techno-economic and life cycle analysis of spirulina-based algal biorefinery is developed. • A minimum selling price (MSP) and GHG emissions are calculated for various pathways. • MSP of renewable fuels is found in the range of US$ 2.5/GGE - $3.94/GGE for various pathways. • GHG emission is found in the range of −59.2 - 147.4 g CO 2-eq /MJ for various pathways. The present study involves techno-economic and life cycle analysis of the production of renewable fuels with co-product from Spirulina platensis using hydrothermal liquefaction method (HTL). In the baseline pathway, the production of renewable fuels from HTL of spirulina is considered along with the utilisation of HTL aqueous phase being recycled back to the algal cultivation system. Various other pathways such as the utilisation of aqueous phase from HTL by catalytic hydrothermal gasification (CHG) and anaerobic digestion (AD) and the production of co-product of C-Phycocyanin (C-PC) (food grade pigment) from the spirulina are studied. Mass and energy balances of the various pathways are conducted using process engineering data available in the literature. It is found that the minimum selling price (MSP) of renewable fuels for the baseline pathway is 3.94 US$/GGE, whereas other pathways show 3.81 US$/GGE, 3.97 US$/GGE, and 2.5US$/GGE for CHG, AD, and C-PC extraction pathways, respectively. A global warming potential of total GHG emissions shows −59.2 g CO 2-eq /MJ, −20.2 g CO 2-eq /MJ, −49.2CO 2-eq /MJ, and 147.4 g CO 2-eq /MJ for baseline, CHG, AD, and C-PC extraction pathways, respectively. These values match with the literature. Further, the sensitivity study is conducted to obtain the most important parameters which are influences the MSP of renewable fuels.