Energy recovery from ricotta cheese whey co-digestion with bovine manure in anaerobic reactors

Abstract

In this research, anaerobic reactors were tested for the treatment and energy recovery of industrial and cattle-raising waste. Four plug flow reactors operated with concentrations of 20% ricotta cheese whey and 80% bovine manure; 40% ricotta cheese whey and 60% bovine manure; 80% ricotta cheese whey and 20% bovine manure; and the control with 100% of bovine manure were tested in bench scale, at room temperature and hydraulic retention time of 30 days. The experiment was conducted for 106 days in fed batches. Biogas volumes between 17 to 27 L day-1 were produced, with an average CH4 concentration of 57 (±1.9) to 60% (±1.44) with energy generation potential from 0.76 to 0.90 in kWh day-1, values that demonstrate the potential of anaerobic co-digestion with ricotta cheese whey and bovine manure for biogas generation and a new alternative for renewable energy production. The average removals of biochemical oxygen demand and chemical oxygen demand were 51 (±13.15) to 78% (±12.00) and 40 (±9.44) to 69% (±20.71), of total solids and volatile solids of 36 (±5.14) to 54% (±11.34) and 44 (±12.53) to 69% (± 9.34), respectively. The pH values were always close to neutrality and alkalinity in ranges suitable for anaerobic co-digestion. The treatment process and recovery of these residues in an anaerobic reactor obtains satisfactory environmental results and can be considered promising.