The Canadian Society for Bioengineering La Société Canadienne de Génie Agroalimentaire et de Bioingénierie Optimizing Solid State Anaerobic Digestion Operating Parameters in the Canadian Prairies -Bench Scale Study Written for presentation at the CSBE/SCG

Abstract

ABSTRACT Solid state (>15% solids) anaerobic digestion (SS-AD) research and system optimization is limited when applied to solid organic feedstocks, specifically cattle feedlot manure. The goal of this study was to establish SS-AD baseline information on biogas production and optimization. The project was split into three components: the design and development of a bench scale SS-AD digester; the investigation of the optimization of the SS-AD process by particle size reduction and leachate recirculation (Round 1); and the investigation of SS-AD inoculation methods and the effects of straw addition and mixing (Round 2). Round 1 looked at the effects of crushing vs. not crushing the manure prior to digestion and examined the effects of no recirculation of the leachate, infrequent (weekly recirculation), and frequent recirculation (3x/week). Results regarding the particle size reduction were inconclusive due to the inherent small size of the vessels. Gas production and methane composition were comparable for all recirculation treatments; however, the weekly recirculation regime showed reduced variability in the results. Round 2 inoculation methods examined were: no inoculation, inoculation using manure digestate, and inoculation using manure digestate leachate. Straw was added to the manure for Round 2 to evaluate how the degree of mixing of co-substrates affected 2 digestion. The added straw was either completely mixed or layered. Results show that the addition of straw lowered the overall biogas production by approximately 25% and the methods of mixing were comparable. The inoculation methods did not significantly affect the total biogas yields; however, employing the digestate method did accelerate biogas and methane production early on. Detailed analytical results and final conclusions for all rounds of study are presented, as well as recommendations for research applications