Rock Creek Digester
General Contractor: McAlvain Group
Design: DC Engineering
Description: The Rock Creek Dairy Digesters is an anaerobic digester system and power generation facility designed to process cow manure from a 12,000 head milking cow operation near Filer, Idaho owned by Bettencourt Dairies. The system utilizes 6 one million gallon concrete vessels that are 80 feet in diameter and approximately 30 feet tall. Other process components include solids separation equipment, a genset building, reception tanks, and associated process mechanical and electrical distribution systems. The project also serves to mitigate odor issues and reduces methane gas emissions by 40,000 tons annually.
Two Cat® 3520C bio-gas generator sets convert the methane rich gas to steadily provide over 2 MW of power which is sold to Idaho Power Company for distribution to the main grid. Rated at 1600 ekW at 1200 rpm, each 3520C generator set is specifically designed to operate on biogas, eliminating the need for fuel pretreatment. One of the generators runs continuously while the other unit runs variable hours following biogas production. Both feed power to an electrical transformer located outside the building. Exhaust heat from the engines is used to heat the six digesters. The controls system design included a PLC based system with remote I/O panels communicating over Ethernet to the PLC. A local server was installed with HMI software configured to display a graphical representation of the system both locally and remotely, as well as historian software with trending and data analysis tools.
Project Cost: $N/A
*Images courtesy of Bettencourt Dairies, McAlvain Construction, Northern Biogas & CAT