Recycling and waste processing company CR&R Environmental Services, headquartered in Stanton, Calif., is in the design and engineering phase for a new anaerobic digestion (AD) system to be installed in Perris, Calif. The system will use a high-solids AD technology from Eisenmann Corp., based in Crystal Lake, Ill.
According to CR&R, the system is permitted to process more than 80,000 tons of organic waste per year in phase one and is expandable to process more than 300,000 tons per year in three additional phases, making it one of the largest AD projects in the United States.
The company reports that biogas produced in the process will ultimately be upgraded for use as a fuel for its fleet of vehicles. CR&R says it will integrate the new plant into existing operations. Feed for the new system will include yard and food waste, which will be processed to produce biogas.
“After a worldwide search, Eisenmann’s horizontal plug flow system stood out as the only technology that was able to provide the highest possible conversion rates for the broadest range of feedstocks,” says Mike Silva, CR&R organics processing project leader. “This flexibility and reliability is essential for the economic success of the project.”
To optimize biogas yield, Eisenmann’s system is fully automated and continuously monitors and optimizes the digestion environment and feed rate, the company reports. The CR&R plant features four parallel primary digesters. Following the pre-processing stage, each digester vessel is automatically fed through conveyors and dosing bins. The digester is equipped with a slow moving horizontal agitator to ensure proper mixing of the feedstock, maximizing exposure to biological colonies and facilitating gas release from the homogenized material. Produced biogas is stored in a flexible, double-membrane gas storage roof within the post-digester.
The biogas is directed from the post-digester to an upgrading unit provided by Greenlane Biogas Ltd. The upgrading process uses water to make biogas interchangeable with conventional natural gas, allowing CR&R to fuel its fleet with compressed natural gas (CNG) and to feed excess natural gas into the pipeline distribution system.
CR&R says when the system is operational, it will be able to maximize the value of its organic materials. To further reduce the company’s carbon footprint and improve the project’s economics, the compressed biomethane also will be used to fuel the company’s vehicles while the remaining digestate, comprising non-digestible fibers and nutrients, will be used as soil amendment.