Macroalgae supercritical water gasification combined with nutrient recycling for microalgae cultivation

The composition of syngas and process water from the supercritical water gasification of macroalgae has been investigated. The potential for using the process water as a source of nutrients for microalgae cultivation was assessed. Saccharina latissima, harvested across the four seasons was gasified in a batch reactor at 500°C and 36 MPa to assess the influence of biochemical content and ash on syngas composition. In addition, summer harvests of four different macroalga were gasified with ruthenium catalyst (Ru/Al2O3). The molar yields of hydrogen and C1-C4 gases from S. latissima increased by 30% in the presence of Ru/Al2O3 with a maximum gasification efficiency of 92% compared with work without these catalysts. Following a series of dilutions, the process water from catalyzed gasification of S. latissima was used in cultivation trials of Chlorella vulgaris and compared to standard growth media. The results indicate the potential to recover process waters from gasification of macroalgae in nutrient management for microalgae.