Improving anaerobic codigestion of corn stover using sodium hydroxide pretreatment

NaOH pretreatment of corn stover was investigated for anaerobic codigestion of corn stover with swine manure to shorten digestion time and improve biogas yield. Different NaOH concentration (2%, 4%, and 6%) at various temperatures (20 degrees C, 35 degrees C, and 55 degrees C) and 3 h of pretreatment time were tested for corn stover pretreatment. A C/N ratio of 25:1 in the substrates (corn stover and swine manure) was employed in the codigestion test. The results showed that the lignin removal rate of 54.57% to 79.49% was achieved through the NaOH pretreatment. The highest biogas production rate was obtained from the corn stover pretreated at 6% NaOH at 35 degrees C produced for 3 h, which was 34.59% higher than that from the untreated raw corn stover. The increase of methane yield was from 276 to 350 mL/g VS. On the average, the reducing sugar content of corn stover decreased to 126.7 mg/g after digestion. Digestion time (T80) of pretreated corn stover was shortened from 18 days to 12-13 days. NaOH pretreatment not only effectively shortened the digestion time for anaerobic codigestion of corn stover with swine manure by removing the lignin from the corn stover but also improved biogas yield of corn stover. The pretreatment condition of 6% NaOH at 35 degrees C for 3 h is recommended for the pretreatment of corn stover.