Supercritical Water Gasification of Lactose as a Model Compound for Valorization of Dairy Industry Effluents

Abstract

The dairy industry effluents, including whey waste and milk-based residues, are enriched in lactose and minor amounts of glucose that could potentially be converted to biofuels and biochemicals. Lactose was used in this work as a model compound of dairy effluents for gasification in supercritical water using a continuous flow tubular reactor. Four parameters impacting supercritical water gasification were studied, namely, temperature (550-700 °C), residence time (30-75 s), feed concentration (4-10 wt %), and catalyst concentration (0.2-0.8 wt %). The best total gas yields, carbon gasification efficiency, H<inf>2</inf> yields, and other major gases (CO<inf>2</inf> and CH<inf>4</inf>) were obtained at 700 °C using a feed concentration of 4 wt % lactose and a residence time of 60 s at fixed pressure of 25 MPa. Furthermore, catalytic lactose gasification involving 0.8 wt % Na<inf>2</inf>CO<inf>3</inf> resulted in maximum H<inf>2</inf> yield (22.4 mol/mol) compared to those obtained by 0.8 wt % K<inf>2</inf>CO<inf>3</inf> (21.5 mol/mol) and noncatalytic gasification (16 mol/mol). © 2015 American Chemical Society.