Biogas and biogas power methanogenic

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emlaurent
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by emlaurent » 17/06/13, 22:58

Hello,

I dig up this subject because it is the closest to my question!

when we make biogas from agricultural "waste", plants, .... I understand that once methanized, the remains of the tank can be composted conventionally to make compost or can be put directly in fields .

But when the waste is partially composed of fats, animal skins, fish - typically canteen / restaurant waste - ... what do we do with what remains after methanisation?
Are they cremated? or can we spread them in the fields without risk?
can we make classic compost?

I have a little trouble imagining that in 30 or 40 days, bones and skins are sufficiently degraded ...

please
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by chatelot16 » 17/06/13, 23:18

the methanizer only methanizes what is methanizable (easier to write than to pronounce) everything else comes out as it entered

so we find at the exit the wood, the bones, the skins the hair the hair the plastic and all the other non degradable waste

so when you put anything in a methanizer the digestate loses a lot of value as fertilizer

it is not necessarily a good solution to throw anything into the tank of the methanizer, which makes the digestate lose its own fertilizer value

an interesting solution that I have not yet seen use: it is to make a small tank in addition to put the waste that we do not want to find in the digestate ... and simply put a pump that circulates liquid between the main tank and this additional tank: suddenly the bacteria will have everything it takes to methanize well in this additional tank, but the waste will remain there without polluting the rest

Another advantage is that it avoids looking for a way to grind these wastes to make them acceptable in the digestate ... once these wastes are methanized thanks to the circulation of the liquid from the main methanizer, they no longer have an odor: they can be landfilled as inert product
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by Did67 » 18/06/13, 08:08

In a "regulatory" installation (authorized and everything ...), this canteen waste must be:

a) crushed (I no longer know by heart the maximum diameter - like 5 mm)

b) hygienized (at least 1 hour at 65 °; here too from memory).

It is obvious that upstream, it is necessary to set up selective sorting systems upon return from the trays.

This is what we are doing at home (see the thread on methanisation at the agricultural college of Obernai).

We are currently working with the services of the Region and the General Council to organize a collection in nearby high schools and colleges ...

Fats are digested. They are even very metahnogenic.

With us, in an installation that operates continuously, by pumping, inert waste (plastic) is excluded. They gradually "fill" the tanks.

Bones are harmless but uninteresting (bone powder is a fertilizer). With us, we avoid but if there is, they are shredded because all the canteen waste is shredded, pumped through a grid, hygienized and introduced into the digester in the form of porridge.

So whether it is plant or animal, the biomass restores the nutrients originally contained in plants (including those that the animals ate, by doing, it is true a sacred sorting).

The danger of animal waste comes from excess nitrogen, which can harm the digester!

Finally, know that animal products, strictly speaking, do not compost (even if at a small dose, they can lower the C / N ratio if it is too high in the presence of too many cellulose or woody plants)
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emlaurent
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by emlaurent » 18/06/13, 20:20

ok, so this type of waste requires prior sorting if we want to be able to compost the digestate or use it as fertilizer.

In fact, I was wondering about the micro-production of methane with canteen / restaurant / private waste on the scale of an urban district.
Are there separation methods after anaerobic digestion and before composting? I suspect a little that not ... but hey
Would the plant parts be more degraded than the bones & skins and it would suffice to do a sifting?

We do not find photos of what comes out of a methanizer : Cheesy:

If not, what is the influence of non-grinding before methanisation? Will this increase the duration of gas production? or that the total production of gas per tonne of DM will be reduced?
Do we have an idea of ​​the gain in gas production vs electricity consumption for grinding?

please
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by Did67 » 19/06/13, 08:13

In what I have described, the shredding is linked to the legally compulsory hygienization (on an "officially recognized" installation - it is an ICPE = installation classified as environmental protection - a bit like a Seveso factory!).

The maximum particle size ensures that the core of the particles is reached by the temperature of 65 ° ...

It is not in relation to the process.

Now, if you look at the process, it depends on whether you operate "continuously", with pumping, or continuously, with "tanks" that you fill, refrigerate, reopen ...

In the continuous phase, the digestate is a "porridge" like a "very thick vegetable soup". And that's how it is at the exit. So easier than composting, it's spreading like slurry.

If you compost them, you need an "ephase speration", a kind of "press". You collect the juices on one side and non-metahnized biomass on the other, rich in woody debris (wood) which ... is indeed composed.

Before going too deep into the process, I advise you to already look into the regulatory aspects. It could be a cold shower.

It's very complicated, because obviously it's gas, so there is a risk of explosion. And it is sanitary because it is necessary to introduce a "break of cycle" (remember the epidemic of E. Coli in Germany when one accused the cucumbers and that it was the water used to germinate soybeans ...). Your digestate will be in contact with plants that may be consumed! And there, the public today demands "total security" and the authorities are extremely picky!

Except clandestine activity, you will not cut it!

C us, 6 years of study and records! Until justifying a few hundred meters from a highway, that our group will not emit more than so and so many ppm of I do not know which benzene derivative!
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by chatelot16 » 19/06/13, 14:45

there is another way of seeing: below a certain number of tonnes of material to be methanized per day, we are not a classified establishment, so we do what we want, almost like the one who balances the m .... from his dry toilet in his compost heap!

but we must be wary of collective projects which multiply the constraints

it is better that a person builds the methanizer on a land which belongs to him and uses the digestate in his own garden

then it is possible to receive methanisable waste from neighbors

anaerobic digestion is a good idea to reduce the need for waste transportation by recycling locally ... but do not push the principle excessively: difficult to do in town without being seen badly by neighbors for odor problem : no smell in normal operation, but this kind of experimental construction can have problems, things to disassemble and empty ... false maneuvers ...

the same system in the countryside next to a farm that has its heap of classic manure going unnoticed! and putting some of the manure from the farm into the methanizer ensures that it operates at full power even if there is not enough other waste
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emlaurent
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by emlaurent » 24/06/13, 14:22

Did67 wrote:Before going too deep into the process, I advise you to already look into the regulatory aspects. It could be a cold shower.

It's very complicated, because obviously it's gas, so there is a risk of explosion. And it is sanitary because it is necessary to introduce a "break of cycle" (remember the epidemic of E. Coli in Germany when one accused the cucumbers and that it was the water used to germinate soybeans ...). Your digestate will be in contact with plants that may be consumed! And there, the public today demands "total security" and the authorities are extremely picky!


chatelot16 wrote:there is another way of seeing: below a certain number of tonnes of material to be methanized per day, we are not a classified establishment, so we do what we want,


Ok, I suspect that the hardest point is surely there!

Below what limit (kind kg of material / day or per year), we would simplify the procedures? See by eliminating all administrative & legal procedures?
Did67, do you have a web link or PDF to start tackling these aspects?

For now, the idea would be to put it in an urban environment with small installations in volume. Installations that would be fed with the waste of the surrounding inhabitants + restaurant.
It is more for the educational or exemplary side than to actually produce energy.

Perhaps we can back it up with a vegetable garden like "food to share" to use the digestate and compost what cannot be methanisable.

It could look like urban farms installed in containers. for example http://20footurbanfarm.blogspot.fr/
There are versions that integrate biogas prod

chatelot16 wrote:it is better that a person builds the methanizer on a land which belongs to him and uses the digestate in his own garden

then it is possible to receive methanisable waste from neighbors


For the moment, no land identified but it is a good idea to have private land.

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by chatelot16 » 24/06/13, 15:25

for the methanisation of manure and other agricultural waste there is neither declaration nor necessary authorization if it works with month of 3 tons / days of waste to methanize: therefore it is possible to make big enough before being subjected to the problem classified establishments

but this limit is provided for agricultural waste ... there is nothing defined for household garbage, which must in principle be picked up by the normal garbage circuit ... anyone who wants to do otherwise rather interest not say nothing

example of figure: a 10m3 tank with 100kg of waste per day to run a generator generating an average power of 1kW

10m3 for the main tank, and 2 or 3 times more for other tank to store the digestate

it's already big, but far from the limit of 3t / day
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by chatelot16 » 30/06/13, 10:27

emlaurent wrote:Finally, the methanation tank needs to be heated permanently, which consumes 10 20% (of memory) of the heat produced.


the proportion necessary to heat the tank strongly depends on the size

the production of gas depand the volume, but the heat loss depand the surface of the tank: the bigger it is the lower the proportion consumed by the heating

when a tank is 10 times larger in size, it makes 1000 times more in volume, therefore produces 1000 times more gas ... its surface is only 100 times greater therefore the heating power 100 times greater is a proportion 10 times lower energy produced

when I calculated 20% of the energy of the gas to heat a tank of 10m3 ca becomes 2% for 10000m3 or 200% for 10litre
https://www.econologie.com/forums/bio-methan ... 12-10.html
it shows that a too small methanizer risks consuming more for its heating than the energy it produces, and that a huge methanizer consumes very little for heating

this calculation is based on a constant thickness of insulation: we can compensate by increasing the insulation thickness of a small methanizer
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by chatelot16 » 30/06/13, 10:57

tank, pump, small generator set modified with gas, everything is possible

the last piece I miss is a good shredder, to chop everything fine and not have any problem

saving grinding is looking for the problems for brewing the tank

I tried different sani grinder for WC: it's too weak, always clogged

there are garbage disposers for sinks, I have seen them work, it looks efficient ... but it is expensive and it consumes high power for a low flow ... and I think it would be too quickly worn out for intensive use

there are shelling pumps: with knives that cut the fibers ... expensive and high power, but the principle and good for making smaller

you also need another type of shredder for large pieces: I think of a harvester style: 2 toothed roller that rotates at 2 different speeds: it's good as a first step, but it lets the long fibers pass, it can be supplemented by a shelling pump
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