Biogas Potential of Duckweed and Spirulina Residues for Renewable Energy

Biogas potential of duckweed and Spirulina biomass is evaluated in a 2018 report by Coudron Carl (INAGRO) and Devlamynck Reindert (Ugent & INAGRO). Duckweed shows a biogas potential of 40.1 Nm³/ton with 57% methane, yielding 86.1 kWh electricity and 99.6 kWh heat per ton. Residues after protein extraction have higher potential—43.9 and 38.8 Nm³/ton—producing 90.6–108.2 kWh electricity/ton. High yields (7.3–9.2 tons/ha DS) result in 3336–4204 Nm³/ha biogas, equivalent to 6.7–8.4 MWh electricity/ha annually. Spirulina residue post-phycocyanin extraction has a biogas potential of 253 Nm³/ton, significantly exceeding pig (72) and chicken manure (64) residues. Residues contain 50% protein and 84% organic matter, making them suitable for biogas or high-value protein use. Anaerobic digestion of duckweed and Spirulina residues supports renewable energy and circular economy goals in Flanders and the Netherlands under the Interreg V De Blauwe Keten project.