In-Line Diffuse Reflectance Spectroscopy Enables Rapid Monitoring of Full-Scale Anaerobic Co-Digestion.

Area of Science:

• Analytical Chemistry
• Environmental Engineering
• Biotechnology

Background:

• Anaerobic codigestion facilities require robust monitoring for optimal performance.
• Traditional analytical methods for digestate and feedstock are often time-consuming and labor-intensive.
• Rapid, in-line monitoring is crucial for maintaining digester stability and maximizing biogas yield.

Purpose of the Study:

• To pilot in-line diffuse reflectance spectroscopy (DRS) for real-time monitoring of anaerobic codigestion processes.
• To evaluate the accuracy of DRS models for predicting key operational parameters in heterogeneous feedstocks and digestate.
• To assess the potential of DRS for improving process stability, biogas yield, and operational decision-making.

Main Methods:

• In-line diffuse reflectance spectroscopy (DRS) coupled with partial least-squares regression was employed.
• Models were developed using data from 42 high-strength waste samples and 146 digestate samples.
• Downsampling analysis was performed to determine the minimum required training samples for effective models.

Main Results:

• Operationally useful predictions (RMSE 10-27%) were achieved for total solids, volatile solids, fats, chemical oxygen demand, volatile acids, and alkalinity.
• Predicted volatile acid:alkalinity ratios served as rapid indicators of digester stability.
• DRS models demonstrated robustness under dynamic operating conditions, including digester instability (foaming, failure).

Conclusions:

• Diffuse reflectance spectroscopy is a viable and potentially cost-effective tool for real-time monitoring of anaerobic codigestion.
• DRS can significantly improve process stability, biogas yield, and operational decision-making.
• The technology offers opportunities to reduce analytical costs by requiring fewer training samples for model development.