Biogas Energy have built an anaerobic digestion (AD) facility at North State Rendering in Oroville, California that is already paying dividends, with uninterrupted biogas generating electricity, fuelling trucks and running boilers.

“For a rendering plant, biogas is a natural fit”, says Brian Gannon of Biogas Energy. “North State Rendering were looking for ways to cut costs, secure new waste supply contracts, and improve wastewater treatment, so creating their own on-site biogas facility was a wise move.  Modifying the anaerobic digestion process to integrate with a rendering plant took some fine tuning, including a very positive modification to the digester’s mixing system, but now, we can see how we got it right”.

From the reception area, the material is pumped into two tanks (40’ diameter by 24’ high), where the first acid-forming phase of the biogas production process takes place.

These heated tanks contain bacteria that break down the material and prepare it for the main digester tank, which stands 64’ tall. When the material is ready, it is pumped into the main digester where biogas-producing bacteria get to work.

Brian Gannon continued: “We had been using submersible propeller mixers inside our main digester, but with our re-design of the tank, we switched to a new system that meets all of our needs. One of the main issues with submersible digester mixing systems is that the equipment is inside the tank, which from a maintenance point of view is a nightmare. The downtime caused by having to open the digester to lift the mixers out for repairs and maintenance caused serious process interruptions and safety issues.