Development of Next-Generation Anaerobic Digestion System

The overall goal of this project is to develop next-generation anaerobic digestion (AD) system that will provide enhanced bio-methane recovery from organic waste through improved process kinetics and stability.  This research broadly addresses the existing challenges faced by Canada’s waste management industry, and actively supports the Province of Alberta’s avid vision in becoming “landfill-free”.  Anaerobic digestion (AD), which represents an attractive option for diversion of organic waste from landfill, produces methane-rich biogas that can be used to meet on-site heat or electricity needs.  However, inferior process kinetics remain an ongoing challenge faced by AD facilities.  Additionally, intermediates (mainly organic acids) from biodegradation of complex organics can accumulate within the digester and lead to process instability.  Hence, further advancements in AD technology regarding process performance and robustness is a critical industry need.

To address these challenges, the Dhar Lab at the University of Alberta has been investigating advanced strategies to promote a resilient and kinetically efficient microbiome towards developing a next-generation AD system.  These strategies include investigation of direct interspecies electron transfer (DIET) and microbial electrochemical technologies (METs) to enhance electric syntropy within electroactive bacteria and methane-producing methanoarchaea.  Enrichment of electroactive bacteria can facilitate altered metabolic pathways during degradation of complex organics, which can provide thermodynamically and metabolically favorable conditions for bio-methane production by methanoarchaea.  DIET can be stimulated within conventional AD through retrofitting conductive additives and thereby enriching electroactive bacteria.  Additionally, MET can be integrated with the AD by incorporating electrodes as an additional electron source and sink along with a small amount of exogenous energy in the form of an applied voltage.  The applied voltage can assist the microbiome to overcome thermodynamic barriers involved in various biochemical reactions towards bio-methane production.  However, further refinement of these ideas in lab-scale followed by a pilot-scale demonstration is required for establishing and maintaining electroactive microbial communities to ultimately realize enhanced biogas production rates at full-scale.

This project focuses on fundamental and engineering aspects of DIET and MET for next-generation digester design and operation. Studies will consist of bench-scale experiments to evaluate process kinetics, thermodynamics, microbial community, and understanding the impact of various process parameters and their optimization.  Our long-term goal is to demonstrate developed strategies in the pilot- and full-scale, which will ultimately stimulate wide-scale adoption of next-generation AD systems for organic waste management.  Overall, the proposed research will enhance the economic and environmental sustainability of AD process by providing (1) shortened digestion time, (2) improved process stability, (3) an increased biogas yield and rate, (4) a lower volume of residuals.