TOC/TN Measurement for the Control and Evaluation of Methane Fermentation of Food Waste using TOC and TN Measurement System

Importance of the Topic

Effective management of methane fermentation of food waste requires precise control of the carbon to nitrogen ratio in feedstock and assessment of digestion efficiency. Quantitative measurement of TOC and TN provides the necessary data to optimize biogas yield and evaluate the nutrient content of fermentation residue.

Study Objectives and Overview

This study by the Industrial Research Institute of Shizuoka Prefecture (IRI Shizuoka Pref.) describes the application of Shimadzu’s TOC and TN measurement system to guide and evaluate methane fermentation of small-scale food processing waste. The work includes a transportable 1 000 L pilot plant and a laboratory-scale test system to verify performance across various waste streams.

Methodology and Instrumentation

• Sample preparation: Ultrasonic homogenization to break down suspended solids, followed by dilution in ultrapure water.
• Instrumentation: Shimadzu TOC-L total organic carbon analyzer equipped with a TNM-L total nitrogen unit and High Suspension Kit for high-solid content samples.
• Measurement conditions: Single-point calibration for TOC (200 mgC/L potassium hydrogen phthalate), IC (100 mgC/L sodium carbonate mixture), and TN (100 mgN/L potassium nitrate).

Main Results and Discussion

• Raw slurry TOC concentration around 5 445 mg/L dropped to approximately 374 mg/L in digestion effluent, indicating over 90 % organic matter decomposition.
• TN levels remained stable (≈212–221 mg/L) before and after fermentation, confirming nitrogen retention and suitability of the effluent as fertilizer.
• Using TOC and TN measurements enables accurate calculation of the C/N ratio, gas generation efficiency, and decomposition rate.
• Compared to chemical oxygen demand (COD), TOC analysis offers greater robustness to sample matrix and reaction conditions, with the added benefit of simultaneous TN measurement.

Benefits and Practical Applications

• Provides reliable control of feedstock composition through precise C/N ratio adjustment.
• Enables rapid monitoring of fermentation performance and biogas yield.
• Supports quality assessment of fermentation residues as nutrient-rich fertilizers.
• Facilitates model case studies for small and transportable methane fermentation units.

Future Trends and Applications

Anticipated developments include integration of on-line TOC/TN monitoring for continuous process control, miniaturization of analysis systems for field deployment, and expanded use in diverse waste streams such as agricultural residues and industrial effluents. Advanced data analytics could further optimize fermentation parameters in real time.

Conclusion

Shimadzu’s TOC-L and TNM-L system delivers accurate TOC and TN measurements critical for efficient methane fermentation of food waste. The approach ensures stable biogas production, high decomposition rates, and nutrient preservation in the residue, offering a scalable solution for sustainable waste management and renewable energy generation.

References

• Shimadzu Application News O65: TOC/TN Measurement for the Control and Evaluation of Methane Fermentation of Food Waste (2018).