Abstracts Biological Sciences

The Effect of Ammonia Pretreatment of Wheat Straw on Biogas Yield by Anaerobic Digestion

by Ernesto Calderon

The effect of ammonia of low and high concentrations on milled wheat straw on biogas production was investigated. Aqueous ammonia was applied to milled wheat straw in a pretreatment process to assess improvement in biogas production through anaerobic digestion. Two different concentrations, 4% (low) and 15% (high), of ammonia were applied to mechanically pretreated wheat straw for 48 hours at 50 °C. Fermented sludge, obtained from Lemvig Biogasanlæg, was used as inoculum and 12 reactors were loaded with a mix of inoculum and pretreated wheat straw in a VS ratio of 4:1. Milled wheat straw pretreated with 15% ammonia produced the highest average yield with 26.5 ml per gVS-1 and a cumulative output of 367ml gVS-1 compared with an average production of 19 ml per gVS-1 and a cumulative output of 289 ml gVS-1 of the 4% ammonia pretreated milled wheat straw. Both produced more than the milling-only pretreatment which yielded 12.8ml per gVS-1. with a cumulative 192 ml gVS-1. The results indicate an increase in production of biogas per gVS-1 for pretreatments using higher concentrations of ammonia. Based on the differences alone it seems that the ammonia pretreatment is effective at increasing biogas yield in a lab setting, however, no statistical significance was found for the data collected with regards to the effect of the ammonia pretreatment on biogas production (p=0.012). A second experiment was conducted examining the physical effects of the ammonia pretreatment which strong suggest that ammonia pretreatment has an effect on the sinkability of wheat straw, eliminating the scum layer formed under usual circumstances by wheat straw added to manure. A correlation between ammonia concentration applied to the wheat straw and sinkability was observed. Advisors/Committee Members: Kaspersen, Bjarke (advisor).