I hope you already know the fact that biogas is a mixture of gases, and its composition changes everyday in a standard anaerobic digesters. And you could not find any such document because its practically impossible to define a precise components and percentage of each gas.

In our lab, we use methane, carbon-dioxide, nitrogen and hydrogen gas purchased separately and make a mixture. Mostly, we use standard for methane/carbon-dioxide 25:75, 50:50, 75:25 etc. And calibrate GC program according to the gas used. For special applications, we use other gases etc. and I am not aware about the exact percentage at the moment.

But basically it depends upon the aim, what we actually want to do.

If it is very less amount and we want specific measurements, we use peak performance 1, which specifically reads the hydrogen amount in gas (enrichment cultures).

For daily or weekly biogas analysis, methane and carbon-dioxide standard is suitable enough. But most of the thing you already know as you are a biogas expert yourself and more experienced than me.

Hi Mr. Singh, I've known since long time ago that biogas is a mixture of gases. Maybe I was not clear enough in my detailed text. We used standard methane to calibrate the GC, also CO2 etc. but I've read in some articles that standard biogas is used to get a complete profile of multiple gases, also H2S and others. Indeed I'm not an expert in GC-MS, I will read more about standard biogas for such calibration. Such mix of gases (in a standard formula) can be purchased as standard biogas. Next week I will search for the articles that I saved, where I read about this in method description (if I remember well they are German authors). Thank you.

Hi dear,

Tahnks for the question. The main components of Biogas are: Methane (CH4), CO2, CO, H2S.

The chemical reaction of methanization and operating conditions are the main factors who control the composition of biogas.

With my best regards!

Adel OUESLATI

http://www.biogas-renewable-energy.info/biogas_composition.html

Many thanks to everyone. It is well known that biogas is a mixture of gases whose composition varies continuously depending on many factors. I will clarify the information that there is a standard biogas for calibration. Practically this is not possible, I do not see how such a standard mixture could exist while the biogas composition can not be constant even for seconds, neither standardized. Therefore calibration should be done individually for each component of interest.

Dear Carmen,

I would not answer your question from theoretical perspective, as you are more expert in this field than me. I would only share the practical experiences in our lab.

We purchase a gas mixture from local gas factory/supplier containing 70% CH4, 28% CO2, and 2% H2S. This is because from our lab's experience, the methane content in the biogas we produced in our experiments rarely exceed 70%. In addition, these gases are those of interest in our lab. (Sometimes we interest in H2, but we use separate gas stream for H2)

Dear Alam, thank you for your kind and helpful answer. Now I have a better view of this practice but I think that for a better precision in biogas quantification, the calibration should be done for individual components, separately. We haven't measured H2S up to now due to lack of standard in calibration, it is not easy, neither economical to purchase standards for all such components and keep the gas cylinders rented for years so as calibrate the chromatograph periodiocally. I suppose there could be a better cost effective solution. Hence my question that was based on some discussions and articles that I've read. Best regards.

I have seen, but can't find, a graph correlating methan/CO2 ratio to reductiom level of the biowaste - fats (highly reduced) giving mainly methane and sugars and cellulose (oxidesed) giving mainly CO2. This might help predciting your results, although obviosly composition change as the digestion process continue.

Yoram

Hello, when measuring the components in biogas by GC, the marking can be made only with high-purity carbon dioxide and methane. Since hydrogen sulfide and hydrogen account for a small proportion in methane, the quantification of these two gases is generally not considered. Most of the articles I have seen are like this.