Effect of leachate recirculation and use of feedstock specific inoculum on biogas production from solid state anaerobic digestion of cattails
Authors: Agnew, J., D. Pratt
Description: Solid state anaerobic digestion (SSAD) systems are an attractive option for agricultural waste products such as manure, biomass and other substrates in Western Canada due to the smaller reactor requirements, decreased water usage and utilization of simple batch systems. Collection and utilization of aquatic plants such as cattails (bulrushes) serves several purposes including extraction of nutrients and heavy metals from watersheds, beautification of lakes and rivers and supply of low-cost feedstocks for green energy production. Most studies on the implementation of aquatic plants as feedstocks for anaerobic digestion are based on a liquid-state anaerobic digestion (LSAD) system. In order to achieve maximum capacity from a cost benefit standpoint, SSAD could be a better approach, but basic operating parameters and biogas production values need to be established. The purpose of this study was to evaluate the biogas production from cattails digested in a solid state anaerobic digester. The study consisted of two bench-scale trials, one to evaluate the effect of weekly leachate recirculation on biogas production, and a second to evaluate the effect of using a feedstock-specific inoculum on biogas production. For each trial, the mixtures consisted of manure only, manure mixed with cattails, and cattails only. In the first trial, each mixture also included a manure digestate as an inoculum (25% by volume). In the second trial, half of the vessels were inoculated with manure digestate and half of the vessels were inoculated with cattail digestate from the first trial. Substrate- specific inoculum had a positive effect on the enhanced digestion of cattails, increasing biogas production by a factor of six. Weekly leachate recirculation only enhanced gas production in those reactors with cattails only. Gas production and quality from reactors with manure only were similar to previous studies, (73 to 135 L CH4/kg VS), while gas production from reactors with cattails only (9 to 104 L CH4/kg VS) were lower than from other biomass materials digested in a LSAD system. For SSAD of cattails, it is recommended that a 50% mixture of cattails and manure be used with substrate- specific inoculum. Further testing should be done with respect to leachate recirculation strategies to accurately determine if recirculation is beneficial for this type of substrate.
Keywords: anaerobic digestion, solid, inoculum, optimization
Technical field: Renewable Energy
Conference name: CSBE/SCGAB 2015 Annual Conference, Edmonton, AB, 5-8 July 2015.
Session name: Bioenergy V - Alternative Energy Production and Efficiency
Citation: Agnew, J., D. Pratt. 2015. Effect of leachate recirculation and use of feedstock specific inoculum on biogas production from solid state anaerobic digestion of cattails. CSBE/SCGAB 2015 Annual Conference, Edmonton, AB, 5-8 July 2015.
Publisher: Canadian Society for Bioengineering
Language 1: en
Rights: Canadian Society for Bioengineering