Multi-scenario energy-economic evaluation for a biorefinery based on microalgae biomass with application of anaerobic digestion

Abstract

Microalgae are a source of biomass that has aroused the interest of the bioenergy industry due to its sustainability potential and maximum use of different abundant natural resources. This research proposes an energy-economic evaluation model for 11 scenarios for a biorefinery based on microalgae biomass, including a final stage of anaerobic digestion. Furthermore, it allows for comparisons between different scales of production, farming technologies and microalgae species, in line with latest industry information. Results are displayed by means of economic (NPV) and energy (EROI) indicators. Almost all the scenarios evaluated returned negative economic profitability, except for the extraction and commercialization of concentrated proteins (the PE scenario with protein sales of US$3/kg). In order to guide future research and investment in microalgae projects, a sensitivity analysis was conducted into the critical variables of the overall process. An optimistic context, led by the increase of the percentage of biomass lipids, allows a minimum biodiesel selling price to be reached which is close to the international value of fossil diesel (US$1/L) for scenarios in which this biofuel is commercialized.