Background

Ramsey and Washington Counties, in conjunction with the St. Paul Port Authority, wanted to examine the opportunities for anaerobic digestion of source-separated organic materials (SSO) in the eight-county Minneapolis/St. Paul, Minnesota, metropolitan area. Organic wastes offer an opportunity to increase the beneficial use of waste materials and develop green power opportunities.

Approach

Foth developed a comprehensive report on the opportunities and constraints of an SSO materials anaerobic digester in the metro area. The report examined the current state of anaerobic digestion technology, current vendors, biogas generation and use options including direct use, biogas to electricity, biogas cleanup and fuel cells, SSO supply and anaerobic digestion facility design. We also examined environmental permitting, economic analysis and project scheduling. Our research was expanded to assess the feasibility of sourcing additional volumes of source-separated food wastes from commercial, institutional and industrial sources in Ramsey and Washington Counties.

Results

The report concluded that an anaerobic digestion facility could be feasible in the Twin Cities provided a steady supply of organic materials could be collected. The sourcing analysis found that the large commercial generators were already served by a mature recovery system for animal feeds (almost half of total food waste was recovered). The primary sources not yet recovered were from restaurants, grocery stores and smaller quantity generators such as educational services.