RITTER has developed a CO2 absorption bottle which reliably absorbs more than 99% of CO2 from biogas. Guaranteed! Without any indicator liquid for absorption limit! This absorption bottle combined with the »RITTER Biogas Batch Fermentation System« provides the ideal solution for professional biogas research.

Operating Principle

The biogas generated in the fermentation bottles flows through a dip pipe into the absorption bottle (»bubbler«) containing the absorption solution. The world-wide unique design of the dip pipe with a bell-shaped “absorption chamber” enables previously unachievable high CO2 absorption rates up to reaching the absorption limit through …

  • the large wetting surface of the biogas within the absorption liquid and
  • the long holding time of the CO2 inside of the absorption chamber.

Another outstanding effect is the fact that the RITTER Absorption System can operate without any absorption liquid indicator showing the limit of the absorption capacity. It is a general problem of such indicators that the colour doesn’t change abruptly but continuously. Therefore, it is difficult for the user to recognize the true limit of the absorption capacity. In contrast to indicator systems the RITTER System guarantees an absorption rate of at least 99% up to reaching the absorption capacity limit. This capacity limit will be indicated by the MilliGascounter by measuring of the volume of methane remaining in the gas stream after absorbing the CO2.

RITTER CO2-Absorptions-Flasche

Technical Specifications

Dimensions absorption bottle (»bubbler«) Volume 250 ml
Wide mouth GL80 with screw cap
Overall dimensions ø D 95 mm x H 145 mm, weight 290 g
Material Borosilicate glass
Dip pipe chamber volume 8.3 ml
Holding time of CO2 bubble in dip pipe chamber dependent on gas flow rate
Absorption solution 3-molar caustic potash solution (KOH 3 mol/ltr in aqua dest.)
Gas in/outlet ports PVDF screw-type tube connection for tube Ø 4i / 6o mm

Absorption Capacity


The absorption capacity is that volume of CO2 which is absorbed until the absorption rate is decreased from 100% (at the beginning) to 99%.
In other words: When the limit of absorption capacity is reached, the gas at the absorption bottle outlet contains 1% of CO2.

Table of absorption capacities at various gas flow rates:

Biogas Input Flow Rate (ml/h)
50 100 200 300 500 750 1000
CO2 absorption capacity, approx. (ltr)* 60% CH4 / 40% CO2 13,4 12,1 8,8 7,9 7,8 7,7 7,6
40% CH4 / 60% CO2 13,5 11,8 8,9 8,5 8,3 8,0 8,1
Absorption capacity limit (ltr)** 60% CH4 / 40% CO2 20,1 18,2 13,2 11,9 11,7 11,6 11,4
40% CH4 / 60% CO2 9,0 7,9 5,9 5,7 5,5 5,3 5,4

* Per bottle filling 250 ml, absorption solution KOH 3 mol
** After the CO2 was absorbed from the biogas, the MilliGascounter displays the volume of the pure methane. The CO2 absorption capacity limit is reached when the MilliGascounter indicates the values the stated in the table above.

Definition of CO2 Absorption Capacity with RITTER Absorption Bottles:

RITTER CO2 Absorption Curve

The above diagram shows the definition of the CO2 absorption capacity with the RITTER Absorption Bottle. The capacity limit is reached when the CO2 absorption rate is reduced from 100% at start to 99%. That means: The CO2 fraction of the biogas at the exit of the absorption bottle ranges between 0% and max. 1%. The remaining CH4 fraction is measured and indicated by the MilliGascounter. Read more about the measured and indicated CH4 volume when reaching the absorption capacity. Below of those stated volume values the user can be sure that the indicated CH4 volume contains a maximum of 1% of CO2.

CO2 Absorption of RITTER Absorption Bottles vs. Surface Absorption Bottles:

RITTER CO2 Absorption Curve Comparison

The above diagram shows the CO2 absorption rates of RITTER Absorption Bottles at various flow rates in comparison to those ones of common surface absorption bottles.


V 2.1 / Rev. 2022-06-24 / Sujeito a alterações.