The techno-economic potential of renewable energy through the anaerobic digestion of microalgae

The potential of microalgae as feedstock for methane production is evaluated from a process technical and economic point of view. Production of mixed culture algae in raceway ponds on non-agricultural sites, such as landfills, was identified as a preferred approach. The potential of straightforward bio-methanation, which includes pre-concentration of microalgae and utilization of a high rate anaerobic reactor was examined based on the premises of achievable up-concentration from 0.2–0.6 kg m−3 to 20–60 kg dry matter (DM) m−3 and an effective bio-methanation of the concentrate at a loading rate of 20 kg DM m−3 d−1. The costs of biomass available for bio-methanation under such conditions were calculated to be in the range of €86–€124 ton−1 DM. The levelized cost of energy by means of the process line “algae biomass – biogas – total energy module” would be in the order of €0.170–0.087 kWh−1, taking into account a carbon credit of about €30 ton−1 CO2(eq).