RESUMEN
Ozone pretreatment of coffee husks (CH) was evaluated to generate hydrolysates for biogas production and to preserve cellulose of the solid phase for 2G ethanol production. Pretreatment variables included liquid-to-solid ratio (LSR), pH and specific applied ozone load (SAOL). Considering single-stage anaerobic digestion (AD), the highest methane production (36â¯NmLâ¯CH4/gâ¯CH) was achieved with the hydrolysate generated in the experiment using LSR 10â¯mL/g, pH 11 and SAOL 18.5â¯mgâ¯O3/gâ¯CH, leading to 0.064â¯kJ/gâ¯CH energy recovery. Due to the presence of toxic compounds in the hydrolysate, the addition of powdered activated carbon (4â¯g/L) to the reactor enhanced biogas production, leading to 86â¯NmLâ¯CH4/gâ¯CH yield and 0.58â¯kJ/gâ¯CH energy recovery. When two-stage AD was applied, methane production resulted in 49â¯NmLâ¯CH4/gâ¯CH, with additional 19â¯NmLâ¯H2/gâ¯CH production, resulting in a net 0.26â¯kJ/gâ¯CH energy recovery.