Hand-held FOS/TAC measurement kit

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Our FOS/TAC measurement kit is based on field-proven measurement equipment with all the necessary laboratory reagents and accessories, making it possible to determine immediately after unpacking:



volatile fatty acid content (FOS, VFA, LKT),

alkalinity (TAC, ALK, OWN),

and calculation of the FOS/TAC ratio.

The FOS/TAC kit can be used in agricultural biogas plants, biogas plants at sewage treatment plants, biogas plants at landfill sites. It allows one of the most important parameters to be determined and analysed systematically in biogas plants – the FOS/TAC parameter. This allows early detection of unfavourable changes in the fermentation process (even before the pH drops), giving the operator the opportunity to take appropriate countermeasures to prevent process breakdown and the serious financial losses that will be associated with stopping or reducing biogas production.


Conducting basic analyses (pH, FOS/TAC) in-house is very economical, as the cost of purchasing a FOS/TAC kit pays for itself after only about one month of use compared to systematically carrying out this type of analysis in an external laboratory.

We also recommend purchasing our FOS/TAC kit for biogas plants which already have automated titrators (Hach Lange, Pronova, etc.), as such a kit is an excellent addition to their own laboratory facilities. It can then be used to periodically verify the correct operation of the titration “machine”, and allows continuity of analysis and FOS/TAC trend following in the event of failure or service of the automatic titrator.


The components used have been tried and tested and are in practical use in operational biogas plants! Over the past nine years, we have selected reliable measuring equipment and components which have proven themselves in the difficult operating conditions encountered in biogas plants.


Making determinations is child’s play. We can assure you that, once you have familiarised yourself with the instructions included with the FOS/TAC kit, anyone without specialist knowledge of how to operate laboratory equipment will be able to handle it. Depending on your level of manual skills, it takes about 15-20 minutes to measure one sample. However, if you still think it might be too difficult we can come and give you the appropriate training.

All consumables (chemical reagents, electrodes, etc.) are widely available and easy to order through online laboratory equipment and reagent shops. The equipment used to compile the FOS/TAC kit comes from reliable, reputable and mostly Polish manufacturers! Finally, you will be able to consciously label the FOS, TAC and FOS/TAC parameters and see where the individual values come from.


Our FOS/TAC measurement kit allows for ongoing monitoring of the fermentation process on site at the biogas plant. This is the most optimal solution, as it allows staff to take immediate corrective action (without waiting for results from the laboratory) if the first signs of destabilisation of the fermentation process are detected.

What is included in the FOS/TAC kit?

  • Schilling burette – 1 pc.
  • pH metric set (electrode for waste water measurement, temperature sensor PT 1000, case) – 1 pc.
  • magnetic stirrer with dipole – 1 pc.
  • stand for electrode and temperature sensor – 1 pc.
  • laboratory scale – 1 pc.
  • sprinkler – 1 pc.
  • laboratory beakers – quantity depending on customer’s needs
  • laboratory elevator – 1 pc.
  • filter strainer – 1 pc.
  • funnel – 1 pc.

Reagents and consumables:

  • sulphuric acid standard solution – 1 l
  • pH 7,00 buffer solution – 1 l
  • pH 4,00 buffer solution – 1 l
  • distilled water – 5 l
  • saturated KCl solution for activation of pH electrodes – 250 ml
  • disposable gloves – 1 kpl.
  • protective goggles – 1 pcs.

Other materials:

  • spreadsheet (MS Excel) to calculate the parameters: FOS, TAC and FOS/TAC ratio
  • Instructions for determining the FOS/TAC parameter
  • Instructions on how to interpret the resulting data based on practical experience!