How to Eliminate CO2 from Biogas?

by Vivaan Pathak Manager

Elimination of CO2 is a crucial part of bio-gas upgradation. It is necessary to remove CO2 from bio-gas so that it can be upgraded to pipeline natural gas quality so that it can be used as a renewable gas. Removal of CO2 from bio-gas is also known as CO2 Scrubbing. This upgraded gas can also be used for vehicle fuel. Bio-gas to CNG plants are highly encouraged by the Indian government these days. There are quite a few reasons why CO2 removal is essential. Let’s take a look.

Carbon dioxide is always found in Biogas due to the degradation decomposition of organic matter by bacteria in the absence of oxygen during the anaerobic digestion process. The Anaerobic process creates a gas, which is a mixture of CO2 and CH4 with some trace amounts of water vapour and H2S at saturation pressure. Let’s take a look at some of the common methods to remove carbon dioxide from biogas:

Pressure swing adsorption also known as PSA
Membrane systems
Chemical carbon dioxide absorption
Water scrubbing
Amine gas treatment method

In every bio-gas to bio-CNG plant, Pressure Swing Adsorption (PSA) is the most popular method out of all. There is a reason why Pressure Swing Absorption is so popular. It is a low cost and low maintenance method.

Water scrubbing is another method that is popular after PSA for CO2 removal. Apart from carbon dioxide, this method removes hydrogen sulphide from biogas as well. Because of their inherent properties these gases are relatively more soluble in water as compared to methane. The absorption process is entirely physical in which the bio-gas is pressurized and fed to the bottom of a column that’s completely packed and water is then fed on top.

In every bio-gas to CNG plant, biogas upgrading is a critical step to produce top-notch quality fuel called bio-methane with a methane (also called CH4) volume greater than 90%. Water scrubbing is also a good technique that is used in the industry.

H2S is biogas is considered to be highly corrosive due to which it requires purification. H2S is also unsafe for human beings and animals. It is not just H2S that can be corrosive. Carbon dioxide (CO2) is also an impurity in biogas which is corrosive in nature and hence it is important to eliminate CO2 from biogas.

If you need more information about why a bio-gas to CNG plant requires a purification system in place, feel free to get in touch with us. We will be more than happy to help resolve your queries and concerns.