Automatic monitoring and early warning approach of process acidification in methane fermentation of food waste due to trace element deficiency

Methane fermentation is an environmentally friendly method for treating organic wastes, and food waste (FW) is highly suitable due to its biodegradability. However, FW systems often experience process acidification caused by trace element (TE) deficiencies, highlighting the need for early-warning (EW) and automatic monitoring. This study proposes an automated monitoring and EW approach using online indicators. Two TE-deficiency-induced acidification episodes and subsequent recovery phases were reconstructed through combined automatic and manual monitoring. Based on the Mann-Kendall trend test, gas production, pH, and oxidation-reduction potential (ORP) were identified as sensitive EW indicators, enabling diagnosis of inhibition type. Principal Component Analysis (PCA) and correlation analysis identified key stability parameters. Results show that online pH, supported by ORP, can reliably reconstruct system stability during acidification, allowing accurate detection of both onset and severity. These findings establish a data-driven foundation for reliable, real-time process supervision in FW methane-fermentation systems.