Evaluation of Anaerobically Digested Biomass in Catalytic Supercritical Water Gasification for Biofuel Production

Abstract

Digested water hyacinth with waste sludge as inoculum were obtained after anaerobic digestion at 35 and 45C. High organic content of digested biomass were evaluated through gasification at supercritical conditions of water in the absence and presence of catalysts (KOH, NaOH, LiOH and K2CO3) with 10 wt.% of volatile solid in feed. Supercritical water gasification of digested biomass was performed in batch reactor system at temperature and pressure ranges of 500-600C and 35-45 MPa, respectively. The highest carbon gasification efficiency, hydrogen and methane yields were reached at 600C (with samples digested at 45C) in the absence of catalyst as 84.6 (g C in gaseous/g C in digestate), 53.0 (mol H2%) and 14.2 (mol CH4%), respectively. High organic content of digested biomass was converted by supercritical water gasification to methane and hydrogen rich gas, and aqueous products (aliphatic hydrocarbons, phenol, substituted phenols, N-heterocyclic, substituted N-heterocyclics, and substituted benzene) that can be evaluated as platform chemicals.