Hello everyone, I analyzed the composition of biogas that was gathered from 25 days of anaerobic digestion. in the result, I had a high percentage of oxygen (22%) and a high percentage of nitrogen (60%). The percentage of methane (14%) and Carbon dioxide were insignificant (0,2%). what do you think? because we have a high percentage of methane and nitrogen the process was not anaerobic or other reasons can be interfered with?
I am not sure about your experimental setup and data collection, but is it possible that your biogas contains ambient "regular" atmospheric air? Usual air composition contains ~21% Oxygen and & ~78% Nitrogen
Dear Narges Golabi,
There is a good chance that atmospheric air was entering your system or measuring device. Given that, as Jannis Viola pointed out, the gas composition correlates very well with atmospheric air composition. It would, however, be beneficial to test the extent of the reaction by COD or VS degradation to find out whether the reaction was inhibited. Thus, the system is not gas tight or whether it occurred during the measurements.
Kind regards,
Roberto
I would suggest that this amount of nitrogen either comes from entrained nitrogen in the feedstock or inadequate management of the biological process. Our work has shown that properly managed, the microbes are rapid consumers of nitrogen.
Hi,
There is no way this system could be anaerobic and yet there was 22% oxygen. Remember during anaerobic processes oxygen may be consumed in little amounts in oxidation reactions. Thus, if it was atmospheric amounts of oxygen could have reduced.
This could have been an error done during sample injection into the the instrumental analysis.
My thoughts..
As an aside question, at what temperature was the process run and what was the pH of the sample?
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