Fast measurement of bio- chemical methane potential (BMP) by NIRS

Significance of the Topic

In anaerobic digestion, accurate and rapid determination of the Biochemical Methane Potential (BMP) is crucial for optimizing biogas yield and process stability. Traditional BMP assays require 30–40 days of fermentation, limiting their applicability in dynamic process control. Near-infrared spectroscopy (NIRS) combined with predictive calibration models offers a promising alternative for fast, reagent-free BMP evaluation.

Objectives and Study Overview

This study aimed to evaluate the performance of a NIRS-based approach using the Metrohm NIRS DS2500 analyzer and the Ondalys Flash BMP® calibration model for rapid BMP prediction of various organic substrates. Validation against standard reference methods assessed accuracy, robustness and potential for process optimisation.

Methodology and Instrumentation

Sample Preparation:

• Ten substrates with reference BMP values between 209 and 443 mL CH₄·g⁻¹ VS were collected (e.g. manure, energy crops, sludge, fats).
• Samples were frozen, dried and ground to enhance homogeneity.

Instrumentation and Calibration:

• Metrohm NIRS DS2500 Analyzer with sample cup and Vision Air software.
• Ondalys Flash BMP® calibration model developed from ≈500 samples across diverse waste categories.
• Calibration built on Partial Least Squares regression covering a BMP range of 20–700 mL CH₄·g⁻¹ VS with 15–20 % model deviation.

Main Results and Discussion

Validation of the Flash BMP® model produced a Standard Error of Prediction (SEP) of 14.3 mL CH₄·g⁻¹ VS and a Root Mean Square Deviation (RMSD) of 14.8 mL CH₄·g⁻¹ VS. Percentage deviations for the ten test samples ranged from 0.5 % to 8.8 %, aligning with the accuracy of traditional BMP assays. Spectral profiles confirmed consistent predictive performance across substrate types.

Benefits and Practical Applications

The NIRS-based method delivers BMP values within minutes without chemicals, significantly reducing analysis time. It enables:

• Rapid feedstock screening for biogas plants.
• Real-time process monitoring and control.
• Resource savings in laboratory operations.

Future Trends and Potential Applications

Advancements may include integration into on-line monitoring systems, expansion of calibration libraries to novel waste streams and development of portable NIR devices for field applications. Machine learning enhancements could further improve model accuracy and adaptability.

Conclusion

The combination of the Metrohm NIRS DS2500 analyzer with the Ondalys Flash BMP® model offers a fast, reliable and non-destructive alternative to conventional BMP assays. This approach supports efficient biogas production management by providing timely methane potential data.

Reference

• Angelidaki I., Ellegaard L., Ahring B.K. (2009) Determination of Biochemical Methane Potential. Methods in Biogas Production.
• Ondalys (202X) Flash BMP® Calibration Model Documentation.