--- title: 'Importance of automatic titration in the determination of the fos/tac ratio for biogas plant control' date: '2026-06-09T09:35:10+02:00' author: tourtools tags: - Innovazione scientifica type: article url: https://www.steroglass.it/en/magazine/importance-automatic-titration-determination-fostac-ratio-biogas-plant-control id: 2575 --- 08 June 2026 [Scientific innovation](https://www.steroglass.it/en/articles?cat=269) ![](/sites/default/files/styles/crop_1350x450/public/images/covers/articoli/2026-06/rapporto-fos.jpg?h=51be5f97&itok=wW7rT1dM) The FOS/TAC ratio is one of the main stability indicators of anaerobic digestion processes in biogas plants. Its reliability critically depends on the accuracy and repeatability of the acid-base titration used to determine the FOS and TAC parameters. Manual methods, still widely used in operational settings, present limitations related to operator subjectivity, endpoint variability, and difficulties in method standardization. The use of automatic titrators overcomes these critical issues, making FOS/TAC analysis a truly effective process control tool. In this context, [Flash2](https://automatictitrator.steroglass.it/en "Flash 2") represents an advanced technological solution to ensure reliable, reproducible, and decision-oriented data. ### The FOS/TAC Ratio as a Process Control Tool in Anaerobic Digestion In biogas plants, the FOS/TAC ratio (volatile fatty acids / total buffer capacity) is used as a synthetic indicator of the equilibrium status of the anaerobic digester. - **FOS** represent the acid load produced during the acidogenic phases. - **TAC** expresses the buffering capacity of the system, mainly due to bicarbonates. The ratio between these two parameters makes it possible to: - identify early signs of organic overload, - prevent acidification phenomena, - optimize substrate management, - maintain consistent biogas production. For FOS/TAC to be truly useful as a process indicator, its determination must be **rapid, repeatable, and comparable over time**. ### Limitations of Manual Methods in FOS/TAC Determination Despite the apparent simplicity of the method, manual determination of FOS/TAC presents several operational criticalities: - difficulty in accurately identifying titration endpoints; - strong dependence on operator experience; - variability of results between successive analyses; - reading and calculation errors; - analysis times incompatible with frequent process monitoring. In particular, FOS determination requires precise control of the titration curve and pH trend—conditions that are difficult to guarantee with manual instruments in industrial environments. ### Advantages of Automatic Titration in FOS/TAC Analysis The use of an automatic titrator represents a fundamental step in transforming FOS/TAC analysis from an indicative measurement into a **true process control tool.** The main advantages include: - **Objective potentiometric identification of titration endpoints,** independent of the operator; - **High repeatability** of analyses, essential for long-term trend comparison; - **Standardization of the analytical procedure,** even with different operators; - **Significant reduction in analysis time,** allowing more frequent monitoring; - **Elimination of manual calculation errors** through automatic result management. These aspects make automatic titration the reference standard for industrial and laboratory applications in the biogas sector. ### Flash2 as the Ideal Tool for FOS/TAC Analysis Flash2, a fifth-generation automatic titrator developed by Steroglass, is designed to meet the operational needs of process control in biogas plants. Thanks to full titration automation, Flash2 allows users to: - perform FOS/TAC analyses easily and reproducibly; - reduce intra- and inter-operator variability; - obtain reliable results even on complex matrices such as digestate; - make the analysis accessible even to non-highly specialized personnel. Digital management of methods and results also enables: - automatic storage of analytical data; - easy comparison of results over time; - support for fast, data-driven operational decisions. ![Flash 2](https://www.steroglass.it/sites/default/files/images/paragraphs/images/2026-06/Screenshot-2026-06-08-alle-16.38.14.jpg "Flash 2") - [Burettes ](#)Up to 2, stepper motor driven, resolution higher than 1.5 M - [Sampling Systems ](#)Stand for single analysis or As Plus automatic sampler with 18/14/30 positions - [Stirring System ](#)High-efficiency mechanical paddle stirrer - [Methods ](#)Up to 30 editable methods (endpoint, equivalence point or inflection point, FOS/TAC, etc.) - [Peripherals ](#)Flash2Data PC connection software (included), printer, barcode reader, conductivity meter, balance - [RGB LED ](#)4 colors indicating instrument status (standby, analysis in progress, error, analysis completed) ### Operational Safety and Laboratory Organization Automation of titration significantly reduces operator exposure to: - chemical reagents; - repetitive operations; - potential procedural errors. Flash2 contributes to improving laboratory and plant organization, allowing FOS/TAC analysis to be integrated into an efficient and sustainable routine control program. ### The solution to overcoming the limitations of manual methods The FOS/TAC ratio is one of the most effective parameters for monitoring the stability of anaerobic digestion processes, but its real usefulness depends on the quality of the analytical data. Adopting an automatic titrator such as Flash2 makes it possible to overcome the limitations of manual methods, transforming FOS/TAC analysis into a reliable, repeatable, and truly effective tool for biogas process control.