Higher methane yields, more profit

FOS / TAC determination in biogas plants easy, quick and cost-efficient



Maximize the methane yields of your biogas plant

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The FOS/TAC ratio is a widely acknowledged key para- The advantages meter for monitoring and controlling your biogas plant. If • Easy: Large touch display and intuitive menu this ratio is not within a window of 0.3 to 0.4, the meth-guidance

ane yield drops, along with the efficiency of your opera-

• Value for money: Swiss quality at a surprisingly tion. In the worst case scenario, the fermentation process low price

in the fermenter can fail, bringing production to a stand-

• Reliable: 75 years of experience in the development still. The Eco Titrator from Metrohm enables easy and production of titration instruments monitor ing of the FOS/TAC ratio – for a continuously • Service and support on-site: Your local Metrohm optimized methane yield and maximum profit for you.

representatives will support you with professional service and application know-how Metrohm provides the method for determining the FOS/TAC value free of charge. Simply load the method via the USB

port, enter the specifications of the electrode and titrant and fill the burette – and your Eco Titrator is ready to go.

There is also the option of connecting a printer via the USB interface or transferring the measurement results to a USB

storage device as a PDF.





FOS/TAC determination – results obtained in 3 easy steps

Background

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The FOS/TAC value enables fast and easy evaluation of the fermentation in the digester and the biodegradation per-formance of the microorganisms. In this analysis, the ratio of the highly volatile organic acids (FOS = volatile organic acids) to the calcium oxide reserve (TAC = total inorganic carbonate) is determined. The FOS and TAC values are determined via titration with sulfuric acid.

Step 1: Sampling

Step 3: Evaluation

and sample preparation The sample is taken from the fermentation tank and transferred to a sealed vessel. This is important, because the organic acids will otherwise volatilize, which falsifies the measurement result.

If there are residues in the biomass, they are removed prior to titration.

Step 2: Analysis

The titration is stopped when pH 2.5 is reached. Fixed point evaluation is used

• Pipette a 20 mL sample to read out the consumption of sulfuric into a beaker

acid up to pH 5.0 and 4.4. The Eco

• Fill the beaker with deionized Titrator calculates the FOS and TAC

water until the diaphragm values, as well as the FOS/TAC ratio, of the electrode is immersed automatically from the acid consump-into the solution

tion.

• Titrate the solution with c(H SO ) = 0.05 mol/L to pH 2.5

2

4

Results of a fivefold determination of the FOS/TAC ratio Determination number

FOS/TAC ratio

1

0.1061

2

0.1086

3

0.1034

4

0.1030

5

0.1047

Mean value

0.1052

Absolute standard deviation 0.0023

Relative standard deviation 2.16%

Order numbers The Eco Titrator Biogas includes everything you need for determining the FOS/TAC value: Titrator, maintenance-free pH-electrode with temperature sensor, buffer solutions and electrolyte solution for the pH electrode.

2.1008.5010

Eco Titrator Biogas

Optional accessories:

2.142.0100

Thermal printer Q3X

G, CH-9100 Herisau

ohm A

witzerland by Metr

www.metrohm.com

, printed in S

11

tudio Silvio Seiler

Subject to change

Design by S

8.000.5327EN – 2019-