Likely a shift in the microbial population. Not sure how it affects the methane production yield. Effect of substrate?

Likely a shift in the microbial population. Not sure how it affects the methane production yield. Effect of substrate?

First, the bacterial shock could happen, and It will change the dominant bacteria population. Surely the rate of bacterial growth may increase due to an increase of temperature in the culture and gas production will increase as well. However, some studies had mentioned that thermophilic is not optimum temperature for AD.

Thank you Dear Professors "Eric D Van Hullebusch and DAR WIN" For replies

You are right, there is a change in the microbial population that causes a failure of methane production according to H. Lindorfer et al in their article entitled "New data on temperature optimum and temperature changes in energy crop digesters" doi: 10.1016 / J.biortech.2008.01.034

They also found that "All strategies for increasing the operating temperature showed negative effects on digester performance, some with serious economic consequences for the operator. It was shown that methane yields at different temperature levels in the mesophilic and sub-thermophilic ranges are similar"

we thought to accelerate the inoculum digestion by increasing the T °, Then it appeared that there was no difference in methane yield.

So, when there is no influence on methane yields, why do researchers use the thermophilic range (wasting energy, is not it?)

Thermophilic range is supposed to provide a higher methane yield, however is a little more unstable than mesophilic; the higher methane yield allows to raise the temperature to 55°C. So my question to you would be for how long have you been operating at thermophilic range, since you already stated that methane production is the same as the obtained at mesophilic range.

Dear Ulises Gonzalez-Miranda,

It is not me who say "that methane yields at different temperature levels in the mesophilic and sub-thermophilic ranges are similar"

It is Mr. H. Lindorfer et al in their article entitled "New data on temperature optimum and temperature changes in energy crop digesters" doi: 10.1016 / J.biortech.2008.01.034

Thanks for the article Mr Djaafri; I will through it and see how can i incorporate to discuss in my research. Regards

Dear  Ulises Gonzalez-Miranda 

You're most welcome

passing from the mesophilic to the thermophilic temperature range accompanied with higher biogas production, however, the tmperature increase should be gradually about 1 degree C per day, I don't know how you control your reactor, but this is what I'm doing in my project

Dear Haider Al-Rubaye

I did not understand what do you mean?

It is true when the T ° increases by 1 degree per day in the same range of T ° (mesophile for example) there is an increase in biogas production.

But from range to range (Thermophil / mesophile) I do not know. because according to the literature in some temperature range there is a digestion process inhibition.

There is complete shift in the dynamics of how the anaerobic digestion system performs.

Unlike thermophilic, the microbes are diverse in mesophilic system. However, when few dominant microbes are strengthened in thermophilic system, the performance is 'really really impressive', as biogas and methane yield increases manifolds.

As many have pointed out, there are still contradictory findings. Most of researchers say thermophilic is better and few differ.

Everything changes after the transition. pH becomes completely different, if you are successful in converting the system to thermophilic condition, pH is above 7.5, 'BUT' if the system is screwed (shock to microbes during temperature increase) pH becomes lower than 6.5.

VFA Profile completely alters! Propionic and butyric acids may dominate in thermophilic system. In unsuccessful cases, with low pH (due to VFA accumulation) obviously biogas yield may be lower, with low methane concentration (compared to mesophilic condition) as well.

The solution is this. Take extreme care during conversion. It is even good if you take months for conversion, though we adopt 1 degree Celsius raise per day during research activity considering the paucity of time. PLEASE INCREASE TEMPERATURE GRADUALLY. Therefore at many cases, the system is operated with chemical buffer action due to inadequate biological action in thermophilic condition.

Still, the anaerobic digester is now a fermentation unit with generation of other gases such as hydrogen.

The above was my research experience.

Thanks,

MK