Lesson 10 - Carbon Dioxide Recovery Technology

In this lesson, we will consider a gas that is as closely associated with brewing as yeast, alcohol, and foam are. It is intimately related to yeast, alcohol, and foam because it is produced by yeast. It is a co-product, along with alcohol, that is produced during fermentation, and is responsible for beer foam formation. It is carbon dioxide!

Specifically, in this lesson, we will look at the recovery of carbon dioxide from fermentation, and the purification and liquefaction of this gas for use in the brewery.

CO₂ recovery considerations

The ownership of carbon dioxide recovery and the operation of the recovery plant in a commercial brewery can differ from company to company. In some cases, they are wholly owned by the utilities department, and in others, owned by the brewing department. Elsewhere, responsibility is split! We will not concern ourselves with such organisational boundaries, but instead, we will simply state the following:

Brewers are both one of the predominant users of recovered CO₂ and also producers of the raw CO₂ gas.

So, whoever is responsible for cleaning the gas up and liquefying it, it is in the interest of brewers to be concerned about how it is done. They will also look at how their fermentation processes and the operation of their fermenters affects recovery.

Brewery uses of CO₂

Carbon dioxide (CO₂) is used for the following purposes:

• To carbonate beer and high gravity blending water.

• To deoxygenate brewing water (if stripper technology is used in the de-aerated water plant) followed by carbonation to produce dilution water.

• To exclude air (oxygen) from various beer tanks (e.g. maturation and bright beer tanks) and containers (e.g. bottles, cans, and kegs).

• To remove air (oxygen) from filter and stabiliser aids.

If the brewery has a carbonated soft drink facility on-site or located nearby, then CO₂ will also be utilised in that facility for product carbonation. We must not forget that carbonated soft drink production does not involve fermentation. This means there is no natural carbonation involved, so any product carbonation needs to come from an external source – perhaps the friendly brewery next door.

Sources of CO₂

Different options are available to source CO₂ for the above uses and other functions. These include:

• Purchased CO₂ – either in single or multiple cylinders of a few tens of kg or purchased in bulk tanks.

  • Such CO₂ is purchased from the marketplace and may be itself from a fermentation-derived source, e.g. other brewing companies selling excess into the marketplace, or as a by-product of the ammonia production process.

• Recovered CO₂ – this is CO_2, which is recovered from a brewery fermentation process, then purified and liquefied and utilised back at the brewery (or associated carbonated soft drink plant).

• Generated CO₂ – this should not be confused with recovered CO₂ (see above), but rather plants which recover CO₂ from combustion gases such as those from a gas burner used in a steam boiler, or in some cases from the combustion of diesel solely to produce CO₂.

  • Such CO₂ will probably require significant purification, depending on the fuel used.

We will restrict our consideration in this lesson to recovered CO₂ only.