quasar energy group - Wooster
|Baseline System||Storage Tank or Pond or Pit|
|Digester Type||Complete Mix|
|Co-Digestion||Food wastes, grass, crop waste|
|System Designer||quasar energy group|
|Biogas Generation||250,000 ft3/day|
|Biogas Use||Electricity; CNG|
|Generating Capacity||600 kW|
The quasar energy group Wooster project features a complete-mix digester that is located on the Ohio State University's (OSU's) Ohio Agricultural Research and Development Center (OARDC) campus in Wooster, Ohio. The complete-mix digester relies primarily on food waste and fats, oils, and grease (FOG) collected from the surrounding area as its feedstock. However, on occasion, dairy manure is codigested with the food waste. The food waste feedstock includes food, FOG, beverage waste, and other wastes. The dairy farm on the OSU campus intermittently sends its animal manure as a codigested waste to the anaerobic digester.
The complete-mix digester has a working capacity of approximately 650,000 gallons and receives a daily volume of 80 to 100 wet tons of feedstock. It operates at a temperature between 98°F and 102°F and has a hydraulic retention time of 20 to 25 days. The biogas produced from the complete-mix digester is estimated to have a methane (CH4) content of 60 percent. On average, the Wooster digester is generating 250,000 ft3 of biogas per day. Biogas from the digester is used to generate electricity and to produce compressed natural gas (CNG) for use as vehicle transportation fuel.
The complete-mix digester is equipped with a 600 kW rated genset that is used to generate electricity. The electricity generated is used onsite and sold locally through a net-metering agreement with OARDC. Approximately 13,000 kWh of electricity are generated daily, and approximately 4,500,000 kWh are produced per year. Additionally, waste heat from the genset is captured, recovered, and used to provide heat to the digester to promote maximum biogas production. Waste heat is used intermittently to heat the digester, typically in the winter and when feeding a new or large load of feedstock to the digester.
The total turnkey cost of the complete-mix digester and genset was $6 million, with the up-front capital cost being funded initially by equity financing. After construction of the anaerobic digester was complete, quasar energy group applied for several grants, which ultimately reduced the total capital cost of the digester to the operator. The grants that quasar energy group received include the following:
- a $500,000 grant from the United States Department of Agriculture's (USDA) Rural Energy for America Program (REAP),
- a $1,500,000 grant from American Recovery and Reinvestment Act (ARRA) Section 1603 Program, and
- a $500,000 grant from Ohio's State Energy Program.
Annualized operations and maintenance cost of the anaerobic digester and genset are estimated to be approximately 3 to 5 percent ($180,000 to $300,000) of the total capital cost of the system. The digester was designed to operate for at least 20 years. The estimated simple payback period is 4 to 6 years.
Currently, quasar energy group employs a scrubbing technology that cleans and purifies the digester biogas to make CNG, which can be used as a renewable transportation fuel for commercial vehicles. At present, a small amount of CNG produced from the digester biogas is used in quasar energy group company vehicles, and the company is preparing to produce more CNG that will be used for a public-access CNG fueling station. Estimated revenue from CNG production is unknown at the present time.
The liquid waste stream (effluent) that leaves the anaerobic digester is used for land application as an agricultural fertilizer on a local farm near the digester, and quasar energy group pays a disposal fee to the farmer.