Renewable Energy Facility
Since 1986, the City of Akron has utilized beneficial reuse technologies to reclaim biosolids from its Water Reclamation Facility, for years operating a composting facility, and then moving to anaerobic digestion in 2013 and the generation of electricity from this renewable fuel source. Approximately 175,000 gallons of blended, thickened sludge from the Water Reclamation Facility is pumped under the Cuyahoga River each day to the Akron Renewable Energy Facility.
“HIGH SOLIDS” ANAEROBIC DIGESTION
The technologies used to manage and process wastewater biosolids continue to be refined to improve efficiency and effectiveness. The City of Akron utilizes a “high solids” anaerobic digestion (AD) process whereby its plug-flow digester typically sees 15 – 18% solids. Conventional AD systems process solids typically in the 3-5% solids range. This allows for a much smaller footprint for the system since the tankage requirements are much less.
The wastewater biosolids are added as a food source to sustain a healthy population of anaerobic microorganisms living inside the digesters. Biogas generated is used to fuel three 600kW combined heat and power units. The electricity generated satisfies 100% of the power requirements for the Renewable Energy Facility, all well as about 40% of the power needs for the Water Reclamation Facility.
The solids remaining following the digestion process are then dewatered and further processed through an indirect dryer, resulting in material that is 95% or better dry solids. These “pellets” meet the “Exceptional Quality Standards” for unrestricted end-use, and are primarily directed towards the wholesale topsoil and planting materials industries. Approximately 12,000 cubic yards are produced annually.