Can I do?

Digester design and construction info

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Parcosan
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Can I do?

Post by Parcosan » Mon Mar 06, 2006 10:14 am

Hi all,

I live in Italy very near to a lot of little farms.
I'm a TLC engineer not used to this stuff, but I'm very interested
to realize this project.
I have NOT a farm, but I would realize a private Anaerobic Digester.
The idea is this:
I take cows manure from little farms near me.
I put manure in the Anaerobic Digester.
Methane is burned, electricity is produced and sold to Electrical company.
Now, since I have not a farm, the SUPPLY, STOCK and ELIMINATING of manure after the digest are very important for me.
Do you think is it feasible a project like this?
I don't think that farms will be interested in building such a digester, 'cause the mean number of Cows in each farm.
I'd like to know some numbers, first of all:

How many kg of manure I've to put in the digester daily
How many water
How long the manure with water has to stay in the digester

After manure finish to produce methane, which is the percentage of manure weight lost and can I sell the output of digester?

Is it a continuous process, or I have to wait that all the manure expire his property to produce methane and then empty the digester and full it again?

Of course, I have to give you the first important number?
How many kWh I want to "produce" each day.
Just to live with my family, leaving my current job.
Let's say more or less 3500-4500 kWh each days

Do you think that transportation of manure will be a prohibitive cost
to realize this project?

Thanks to all,

Parcosan

Parcosan
Posts: 4
Joined: Mon Mar 06, 2006 9:49 am

Digester must be loaded on a regular basis

Post by Parcosan » Wed Mar 08, 2006 2:50 am

I'm reading some interesting articles on the topic, and I understood that the digester must be loaded with manure on a regular basis to ensure a continuous supply of food for the anaerobic bacteria. This make my dream very hard to realize, 'cause I've no cows.
So now the question is: stocking manure is possible?
If I stock a large amount of manure in opening place, can I use it daily or the manure has to be putted in the digester just after the expulsion from cows?

Thanks to anybody can give me an aswer

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nathan_lamothe
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Post by nathan_lamothe » Wed Mar 08, 2006 9:12 am

Depending on the systems you use. It is certainly possible to use a batch process, but with cow manure the retention time is relatively low, so that would lead to a lot of handeling...open digestter, empty digester, refill digester, close digester, wait four days and repeat...

If you can predict a rate of manure accumulation... ie one truckload a day, you could build a plugflow digester to accomodate it.

Storage of manure would I suppose be a possibility, but you would run into issues with composting (aerobic digestion of the manure) and would likely want to store it relatively dry, which means you would be adding lots of water before adding it to the digester.

It'll come down to the type of cattle operations near you, how the farmers collect manure, and how much you want to put into the project.

Bob is better at this sort of rough calculation than I am.. I'll go rustle him up...

Parcosan
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Joined: Mon Mar 06, 2006 9:49 am

Post by Parcosan » Wed Mar 08, 2006 9:27 am

Thanks a lot for your answer.
I think that number of variables are increasing too much.
Take into account that farms are very little in my village, so
I should pay a lot in order to transport 1 track of manure each day
from farms to my digester.
And then spend money also to take away the manure after the digestion.
The idea could be:
asking to the municipality if they can make me use human refusal.
Connecting to the city pipe of human refusal, putting the refusal inside the digester, use it and then discard again the refusal in the city pipe after the usage. In this view, the problem could be just
"Realize the digester near a collecting pipe of refusal, sufficiently big to assure me the needed amount of daily refusal"

Isn't it?

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nathan_lamothe
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Location: Joussard, Alberta, Canada

Post by nathan_lamothe » Wed Mar 08, 2006 12:45 pm

I was just speculating at the 1 truck a day. Maybe you don't need that much, maybe you need more...

Ideally, from my point of view what we should all be working on is lobbying municipal governments to make full use of the sewer waste passing through their systems. If every town used anaerobic digesters to process their waste, and used the methane produced to heat & power the municipal buildings...

The world would appreciate it.

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Bob
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Post by Bob » Thu Mar 23, 2006 12:49 pm

Hi Parcosan,

Reading through your project description and questions about feasiblity raises a number of questions for me:
  1. What do the local farmers do with the manure now? Do they spread it on the fields? Is it presently stored in tanks or pits that you could easily pump from?
  2. What would be the average distance between your facility and the farms?
  3. Do you have an estimate of the number of farms and the number of cows (or other animals?) per farm?
  4. What is the local cost and/or availability of electricity?
  5. What is the local cost and/or availability of fuel gas?
  6. What is the local cost of labor -- i.e. hourly rate to pay a truck driver and digester operator, etc.
  7. Is there a local market for the treated sludge (fertilizer)?
While an interesting idea, without knowing more, I'm guessing that the labor cost and fuel cost used to transport the manure could possibly make it unfeasible. Though if you were to combine the idea with a greenhouse operation, using the fuel gas to operate it, it might add some value. Are there valuable greenhouse crops that are not locally available that there might be a market for?

Parcosan
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Joined: Mon Mar 06, 2006 9:49 am

Post by Parcosan » Thu Mar 30, 2006 3:08 am

Hi Bob and thanks for your post.
These are the answer:
What do the local farmers do with the manure now? Do they spread it on the fields? Is it presently stored in tanks or pits that you could easily pump from?
Local farms take manure at the air as heap. Part of it's used spreading on the fields. Part of it is taken from a guy that sell the manure to compost industry.
What would be the average distance between your facility and the farms?
Well, should be possibile to install the system near a farm. The other farms are in a radius of 10 km.
Do you have an estimate of the number of farms and the number of cows (or other animals?) per farm?
In Italy farms are not big. The medium number of cow is 100-120
There are also pig farms in the same radius. For the pig farms, probably the medium number is higher, let say 200 pigs each farm
What is the local cost and/or availability of electricity?
Well if you find a way to produce electriciti, the national company can buy at 9 Euro cent each kWh, but after you realize 400.000 ?, the selling price fall down to 7 Euro cent each kWh.
A family in Italy pays 0,16 ? each kwh
What is the local cost and/or availability of fuel gas?
Fuel gas diesel to transport manure is 1,2 Euro each liter
4.54 liters = 1 gallon

What is the local cost of labor -- i.e. hourly rate to pay a truck driver and digester operator, etc.
I dont' want to pay operator to manage the digester. I would do be myself. I just want to pay freelance truck driver that bring me manure.
Is there a local market for the treated sludge (fertilizer)?
The nearest market is 40 km distance, but there are jet some guys that do this for job. The idea is to sell directly manure to these guys.
So the path of manure now is: cow-farm heap-stock of guy- fertilizer
The new ideal path should be: cow-farm heap- my digester-stock of guy- fertilizer
if you were to combine the idea with a greenhouse operation, using the fuel gas to operate it, it might add some value
Are there valuable greenhouse crops that are not locally available that there might be a market for...

I didnt' understand this concept, could you explain to me?
Thanks a lot

Parcosan

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