A preliminary study of simultaneous lime treatment and dry digestion of smooth cordgrass for biogas production

The technical feasibility of simultaneous lime treatment and dry digestion (SLTD) of smooth cordgrass in a leaching bed reactor at 55 ± 1 °C is discussed. SLTD was carried out in a single reactor with a high initial biogas production rate and volatile solids (VS) removal rate. Biogas yields reached 283.9 and 192.7 mL/g VS, with 10.0 and 9.5 L/d maximum biogas production rates for asynchronous lime treatment and dry digestion (ALTD), and SLTD, respectively. VS removal efficiency reached 69.0% and 71.9% for ALTD and SLTD, respectively. 83.7% and 99% total biogas yields were obtained at the beginning of 30 days digestion for ALTD and SLTD, respectively. The biogas production rate constant gradually reduced with the reduction of easily biodegradable material. Inhibition of anaerobic bacteria occurred at the SLTD experiment during dry digestion, as shown by very little total volatile fatty acid and biogas production after day 20. Sodium, potassium and calcium ions were not responsible for SLTD inhibition.

► Simultaneous lime treatment and dry digestion (SLTD) was successfully carried out.
► 192.7 mL/g VS biogas yield and 71.9% VS removal was obtained in SLTD.
► Inhibition of anaerobic bacteria occurred at SLTD.
► Sodium, potassium and calcium ions were not the reason of SLTD inhibition.