An insight into carbon balance of product streams from hydrothermal liquefaction of Scenedesmus abundans biomass

Abstract

Lab-scale hybrid loop airlift photobioreactor (HLALPBR) was used to culture microalgae Scenedesmus abundans in domestic wastewater. The highest biomass productivity of 209 mg L−1 d−1 and concentration of 3.55 g L−1 were achieved. S abundans could eradicate chemical oxygen demand, dissolved inorganic nitrogen, and dissolved inorganic phosphorus by 80.19%, 90.73% and 86.31% respectively from domestic wastewater. Later, hydrothermal liquefaction of algal biomass yielded 35.5 wt% of bio-oil. Carbon mass balance between various product streams showed that per g of algae about 0.46, 0.15, 0.963 and 0.35 g of CO2 was sequestered by bio-char, bio-gas, bio-oil and post-HTL wastewater product streams respectively. Since bio-oil has low N and O content and higher heating value of 36.52 MJ/kg, those can be upgraded to transportation fuel. The conversion of S. abundans to bio-char as a carbon sink has been proposed for reducing emissions and increasing the sequestration of atmospheric carbon dioxide.