In this study, the anaerobic digestion of waste brown grease (BG) in a pilot-scale system was investigated. A mean COD removal of 58% and a mean VS removal of 55% were achieved. The organic removal efficiency was comparable with those found in typical solid digesters. Kinetic analysis showed that the pseudo-first-order degradation rate constant of BG was in the rage of 0.10–0.19 d−1. After anaerobic treatment process, the effluent had a consistent effluent organic strength (COD ∼ 10,000 mg L−1) that can be treated aerobically. It was concluded that BG was a readily digestible substrate as a sole substrate.
The pilot-scale system produced biogas of excellent quality (75% CH4 content), with a methane yield in the range of 0.40–0.77 m3-CH4 kg-VSremoved−1. The addition of paper mill waste streams (fouls condensate and screw press liquor) as the co-substrates did not adversely affect the methane yield. BG has the industrial potential to be anaerobically treated as an energy feedstock and there has been ongoing commercial effort to build large-scale digesters using BG as the primary substrate. Using BG for biogas production could serve as a profitable model for converting waste to renewable energy.