Choosing the correct dosage of Bicar®Z to optimize methanation
Methanation works like a biological ecosystem (comparable to the rumen of the cow) and involves a series of steps that transform organic matter into methane (CH4) and CO2.
Adding Bicar®Z continuously, or as a curative or preventive measure, provides an effective solution to the problems of acute acidosis, enables the operator to prepare for substrate changes and improves the yield of the methanation process.
Recommended dose in the event of acidosis
Acidosis in the methanizer manifests itself in the following ways:
- a drop in pH to below 6.8-7.0,
- a drop in buffering capacity to below 100-150 mmol/L or TAC* values below 6000-7000,
- a rapid increase in the FOS**/TAC ratio to over 0.7.
In the event of acidosis*** , it is strongly recommended that Bicar®Z be added according to the following doses:
- 5 to 10 T for facilities fed with liquid manure,
- 8 to 20 T for facilities fed with energy crops.
Recommended dose for preparing substrate changes
Changes of substrate are likely to result in imbalances in the flora in the digester and modify the acid-base equilibrium of the environment:
- a drop in pH to below 7.0-7.2,
- A drop in buffering capacity to below 100-200 mmol/L and TAC values below 8000-10,000,
- a rapid increase in the FOS/TAC ratio to over 0.7.
When changing the substrate***, it is recommended that Bicar®Z be added in the following doses, 3 days before to 3 days after the change of substrate:
- 5 to 10 T in 2 to 3 doses over the course of the 6 days for facilities fed with liquid manure,
- 5 to 15 T in 2 to 3 doses over the course of the 6 days for facilities fed with energy crops.
Recommended dose for increasing the yield of the methanation process
Adding Bicar®Z allows the performance of the methanizer to be improved. The quantities required*** depend on the retention time and the type of substrate:
- for a facility fed with 100% maize, add 100 kg Bicar®Z per day,
- for a facility fed with 70% maize and 30% liquid manure, add 50 kg Bicar®Z per day,
- Generally, allow 1.5 T (one 25 kg bag per day for 60 days) to 7.5 T for the duration of the retention time (40 to 60 days).
* The TAC, or complete alkalinity titration, defines the buffering capacity of the environment. The lower the TAC, the less the ecosystem is able to buffer a drop in pH.
** The VOA value (standing for volatile organic acids, or FOS in German) represents the concentration of organic acids in the environment.
*** The recommended doses of Bicar®Z for methanation are based on empirical observations of a methanizer measuring 2500 m3, and for a retention time of 40 to 60 days. The use of Bicar®Z is the sole responsibility of the user. For further information, or for recommendations tailored to your facility, you can contact one of our experts in methanation.