Advancing Multi-Stage Anaerobic Digestion Technologies through Improved Hydrolysis Processes

Existing and proposed regulations requiring organic waste diversion from landfills are driving an ever increasing need for sustainable waste management technologies.

Anaerobic digestion (AD) can produce bioenergy and represents the most sustainable organic waste management technology. However, AD is not widely applied to organic fraction municipal solid waste (OFMSW) in the U.S. because currently available technologies are not economically viable. Thus, advancements are needed to improve AD profitability. Our industrial collaborators Harvest Power and GICON (commercial providers of a multi-stage AD technology) have identified development of improved hydrolysis processes as a critical industry need. A specific challenge for achieving maximum hydrolysis rates of food wastes is elevated ammonia and salinity, which are known to inhibit microbial processes. To overcome this challenge, we have been developing advanced microbial inocula that are capable of achieving high rates of hydrolysis even in the presence of elevated ammonia and salinity, and we have recently shown in batch-scale studies with elevated ammonia and salinity that hydrolysis rates can be significantly improved (4- to 10-fold as compared to with standard inocula) using these specifically developed microbial seeds. However, future research is needed to develop technology for establishing and maintaining these optimized microbial populations in large-scale, multi-stage AD systems to realize improved hydrolysis rates at full scale.

Specific project objectives are:

• Evaluate leachate-bed reactor operational approaches to control the microbial populations in AD reactors at startup and over the course of reactor operation via optimizing both initial seeding methods and process operation to maintain key organisms.
• Develop operational approaches to maintain increased hydrolysis rates during long-term operation.
• Conduct an economic analysis to evaluate profitability of developed improved hydrolysis processes.