Investigating the Performance of Anaerobic Co-Digestion of Primary Sludge and Acid Whey Using a Twin Pilot Scale System

Anaerobic Digestion (AD) has proven to be an effective method for transforming organic waste into biogas, a renewable energy source that can play a crucial role in reducing our dependence on finite fossil fuels. Despite its widespread use, mono-digestion, where a single substrate is utilized, is prone to several drawbacks, including process instability, limited feedstock options, and low biogas/methane efficiency. To overcome these limitations, anaerobic co-digestion (AcoD) has emerged as a promising alternative. In AcoD, multiple substrates are digested simultaneously, leading to a more stable process, a greater variety of feedstock options, and an increased biogas/methane yield. The co-digestion of wastewater treatment plant (WWTP) sludge and food processing wastes has proven to be a popular area of research in AcoD, offering a balanced mix of carbon, nutrients, and minerals for optimal digestion. This study investigates the performance of AcoD between primary sludge (PS) and acid whey (AW) compared to PS mono-digestion, using a twin 15 L pilot scale continuous flow complete stirring tank reactor (CSTR) system. The experiment was carried out at a mesophilic temperature (35 °C) with an increasing organic loading rate (OLR). The results suggest that AcoD of PS and AW is a promising approach as optimal process conditions were maintained while the biogas yield increased.system. The experiment was carried out at a mesophilic temperature (35 oC) with an increasing organic loading rate (OLR) (>2 g VS/L-d). The results suggest that AcoD of PS and AW is a promising approach as optimal process conditions were maintained while the biogas yield increased (>10%), making it a cost-effective solution. Acknowledgements The research leading to these results has received funding from the European Union’s Horizon 2020 Research and Innovation programme under grant agreement no 958266.