Anaerobic Digester using Horse Manure

Digester design and construction info

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nobloominbroom
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Anaerobic Digester using Horse Manure

Postby nobloominbroom » Tue Jan 19, 2010 9:24 am

I live on a island in (Puget Sound area, southwest of Seattle), Washington. I muck at a barn to get some extra spending money and starting thinking about all the horse manure around me. There has to be a better way than just letting it sit and smell. I began investigating anaerobic digesters as a means of solving some environmental problems.

Everyday the paddocks are mucked. The waste includes manure and stall waste (wood shavings) with urine. The paddock surface is dirt, gravel and rocks. As the manure is scooped up it comes with a bit of everything. I've thought that a batch method would work out best. I've so many questions. Would appreciate any input.

1) Why can't old waste be used?
2) When the manure is mixed with water prior to placing in digester what consistency should be attained?
3) Does the AD process need to be dosed with bacteria initially or are the different kinds of bacteria naturally occurring in the waste?
4) I'd like to use the methane in a generator? Any recommendations of generator manufacturers for sizes of 1 - 5kW/240V/3ph?
5) What storage methods could be used to keep the manure suitable until loaded for the next batch? (30 days?)
6) The pastures are mucked once a week. Can this manure be used in AD?
6) How do you know when the process is complete? What instruments are used?
Thank you.

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Bob
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Re: Anaerobic Digester using Horse Manure

Postby Bob » Sun Jan 24, 2010 9:59 am

1) Why can't old waste be used?
Can't it?
2) When the manure is mixed with water prior to placing in digester what consistency should be attained?
About 6% solids -- like thick whipping cream.
3) Does the AD process need to be dosed with bacteria initially or are the different kinds of bacteria naturally occurring in the waste?
Yes. While there are naturally occurring bacteria in the waste it probably isn't viable. It needs to be fresh. To start a digester, start with about a 50/50 mix of inoculant (viable bacteria) and feedstock, and as the population grows, gradually add more feedstock (horse manure/straw)
4) I'd like to use the methane in a generator? Any recommendations of generator manufacturers for sizes of 1 - 5kW/240V/3ph?
It largely depends on purpose & budget. How many hours/year will it run?
5) What storage methods could be used to keep the manure suitable until loaded for the next batch? (30 days?)
Why not digest it? You could have two (or more) batch digesters and alternate between them.
6) The pastures are mucked once a week. Can this manure be used in AD?
Yes. But it might take more prep work (screening out sand/dirt, etc.)
6) How do you know when the process is complete? What instruments are used?
When it stops making enough gas to be useful. No instruments required.


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