Progress 06/15/10 to 02/14/11
Outputs
OUTPUTS: 1) Build on prior research to optimize the design of SS-AD reactors and test a pilot scale system. The SS-AD reactor will be a single tank, batch/continuous flow design. The start-up and production phases of the reactor will be based on the recommended operating ranges from the OSU lab test results. Biogas and methane production will be measured and input parameters will be changed to optimize production throughout the start-up and production phases. Additional feedstocks will be lab tested as they become available to determine their suitability for dry digestion. 2) Determine acceptable operating ranges for process variables. We have compared the performance of solid state anaerobic digestion of corn stover with effluent from three different sources (Buckeye seed from a food waste digester, Akron seed from a municipal biosolids digester, and Bridgewater seed from a dairy waste digester). The biogas yields of three feedstocks (corn stover, wheat straw, yard waste, and leaves) in solid state anaerobic digestion were also studied. The effects of substrate/inoculum (S/I) ratios (2, 4 and 6) and NaOH addition on the performance of the digestion were also studied. 3) Characterize and evaluate applications for the digestate. The digestate for each of the above tests were characterized with total solids, volatile solids, total nitrogen, total carbon, cellulose, hemicellulose, and lignin contents. Applications for the digestate are twofold: land apply as a farm fertilizer or mix with additional dry feedstock to create compost. PARTICIPANTS: Clemens Halene - Vice President of Engineering, quasar energy group. Management, operations, and product development with executive leadership role and direct influence on performance and growth of project. Dr. Yebo Li - Assistant Professor, Department of Food, Agriculture, and Biological Engineering. The Ohio State University OARDC John McClellan - Project Manager on demonstration scale digester, quasar energy group TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The highest methane yield about 105 L/kg VSfeed was obtained with corn stover at S/I ratio of 3. At S/I ratio of 4, the highest methane yield about 82 L/kg VSfeed was obtained with wheat straw. Yard waste has the lowest methane yield. Due to the difference in bulk density of each feedstocks, more VS could be loaded per unit working volume with feedstocks having higher bulk density. Methane productivity from SS-AD of corn stover(10.8 L/L) remained as the highest among four feedstocks tested. This was followed by SS-AD of leaves with an average methane productivity of 9.1 L/L, which was only 16% less than that of corn stover. Methane productivities of both wheat straw and yard waste were considerably lower. Methane productivity attained in SS-AD of wheat straw was 7.8 L/L, an average of 29% less than that of corn stover. The lowest methane productivity was observed with SS-AD of yard waste (S/I ratio = 2 and 3) which was approximately 36% less compared to that of corn stover. Compositional analysis was performed on content in reactors at the beginning and after 30 days digestion of SS-AD. Changes in the composition were expressed as the weight of each compound measured based on initial loading level of 100 g TS. The highest cellulose degradation was observed with SS-AD of corn stover, about 41% of cellulose was degraded. This was followed by wheat straw with 36% cellulose degradation. Significant lower cellulose degradation was noted with SS-AD of yard waste and leaves (6 and 16% respectively). Similar degradation trend was noted in hemicellulose, the highest degradation (36%) was obtained with SS-AD of wheat straw followed by corn stover (34%), respectively. Substantial lower hemicellulose degradation was noted with SS-AD of yard waste and leaves (7% and 21%); respectively. The degradation of holocellulose was closely related to the lignin content of each lignocellulosic biomass feedstock. Higher degradation in holocellulose was associated with lower lignin content. At S/I ratio of 2, reactors inoculated with effluent from food processing waste digester had the highest methane yield in the first 10 days. However, the methane production of reactors using this seed was lower than that of a digester fed with dairy manure seed in the last 20 days. A probable reason could be that the first seed was the effluent from a food waste digester and thus may have less cellulose-hydrolyzing bacteria. After the readily digestible organic matter was consumed, hydrolysis rate became a limiting factor. This also might explain why a S/I ratio of 4 has higher gas production than a S/I ratio of 2 for first seed, since there are more readily digestible carbohydrates. Dairy manure effluent had the highest methane yield at S/I ratio of 2. Food waste effluent had the shortest start-up time. The daily methane yield peaks of NaOH treated leaves were much higher than that of the control (no NaOH addition). Due to the inhibition of Na+, the methane peaks were delayed with the addition of NaOH. When the NaOH concentration increased from 2.0% to 5.0%, the appearance of methane production peak was delayed from the third day to the 16th day.
Publications
- No publications reported this period
|