Anaerobic digestion (sewage sludge)

[Clay]

Hello.

I have a few questions about anaerobic digestion of sewage sludge:
-Already for the nature of the substrate: is dehydrated sludge (packaging: polymer) favorable for recovery from biogas [compared to so-called liquid sludge]? (A priori yes: dehydration does not act on the fermentation power of the substrate)

-The dryness of the digestate depends on that of the substrate used, so if we use pasty sludge as a substrate it will not be necessary to carry out a dehydration operation on the digestate (digestate directly to composting).

I hope the questions are clear.


Goods.

[bernardd]

If you already have a dehydrated mud, you might as well burn it directly, no need to go through the methanisation stage: it will be more effective at all levels.

What is its residual moisture content?

[Clay]

What is its residual moisture content?

I don't have the exact value yet, I'm counting on a value of 80%.

If you already have a dehydrated mud, you might as well burn it directly, no need to go through the methanisation stage: it will be more effective at all levels.

Biogas recovery is an imperative, do you find this unsuitable (on pasty mud)?

Ps: And for the second question?

Goods.

[bernardd]

What is its residual moisture content?

I don't have the exact value yet, I'm counting on a value of 80%.

So still very humid.

Biogas recovery is an imperative, do you find this unsuitable (on pasty mud)?

Why is it imperative? The biogas is going to be burned anyway, right?
So as much to burn the whole, at least all that is organic will be burned / disinfected, with a better yield than fermentation, while taking less time, therefore less storage.

You can also make pellets if storage is necessary.

Ps: And for the second question?

sorry, i don't understand it: i don't know what the word digestate and substrate mean in your context. So I left it to others :-)

[Clay]

Why is it imperative? The biogas is going to be burned anyway, right?

There was a misunderstanding: when I speak of imperative I mean by that in my case energy recovery by biogas production has been imposed. This puts my first question in context:
I know that anaerobic digestion is generally applied on very wet sewage sludge (95%), as in my case the sludge is a little less wet (already dehydrated) I wonder if at least the digestion of this sludge is as effective (see binding) as what is done for liquid sludge?

sorry, i don't understand it: i don't know what the word digestate and substrate mean in your context. So I left it to others :-)

Substrate: mud at the entrance to the digester.
Digestate: mud recovered at the outlet of the digester.

[bernardd]

There was a misunderstanding: when I speak of imperative I mean by that in my case energy recovery by biogas production has been imposed.

It was not a misunderstanding: I had felt the notion of power, hidden in the context.

I never accept an unjustified decision.

And even more when the available evidence shows that it has a high probability of not being justifiable.

It is personal responsibility that prevents abuse and disaster.

Substrate: mud at the entrance to the digester.
Digestate: mud recovered at the outlet of the digester.

OK thank you, I understand better, but I have no validated elements for your question.

[Clay]

And even more when the available evidence shows that it has a high probability of not being justifiable.

I would like to have some arguments?
You seem to recommend incineration in general (not only in my case)


-Dehydrated sludge does not reduce their fermentation power (quantity of organic matter)
-The abatement rate should be higher than that of liquid sludge, therefore a smaller quantity of sludge to be stored.

It is personal responsibility that prevents abuse and disaster.

We are not there anyway!


Good evening bernardd.

[bernardd]

I would like to have some arguments?

Yes, I understand your situation well: having such a decision imposed without having received an argument to justify it is rather embarrassing.

One could imagine that to choose this solution, even a quick comparison with the complete incineration solution was made.

If you have not received these arguments, it may be that it was not made, which calls into question the competence of those who impose this decision on you. Maybe you should ask them for this comparison? It will be interesting to understand it.

You seem to recommend incineration in general (not only in my case)

Generally speaking, no, I don't think so.

But whether it is in the case of producing energy or in the case where it is necessary to get rid of the sludge, I have not yet found the advantage of going through the intermediate stage of a fermentation with gas production.

But maybe you're going to show me the interest, and I would have learned something.

Furthermore, it is certain that it would be even more effective not to put this waste in water, and to treat it at the source, in each house: it will come, I hope!

It is personal responsibility that prevents abuse and disaster.

We are not there anyway!

Where are we ? look better around you. Who is silent consents.

[Clay]

Re.

Where are we ? look better around you. Who is silent consents.

Yes we are not there (stage of realization): it is a study, I think my presence on the forum (in order to glean info) is far from resembling a state of resignation!

You seem to recommend incineration in general (not only in my case)

Generally speaking, no, I don't think so.

But whether it is in the case of producing energy or in the case where it is necessary to get rid of the sludge, I have not yet found the advantage of going through the intermediate stage of a fermentation with gas production.

It seemed to me that you were not a supporter of biogas!

But maybe you're going to show me the interest, and I would have learned something.

Anyway it is up to date, I remind you that a lot of resolutions have been taken in order to substitute biogas for incineration.
(At the risk of force-feeding you, the major argument remains the ecological balance comes the cost of the investment then the control of the odor nuisance.)


In short, in order to restructure the subject of my request, I would like to collect the following information:
For 80% wet sludge.
-The average organic matter content (% MO).
-The dryness of the digestate collected.
-The rate of abatement.

Goods.

Kind regards.