Re: Biogas digester

Posted by Zach Bouchard on February 22, 2009 at 17:22:03 from (64.136.27.226):

In Reply to: Biogas digester posted by Farmall_51 on February 21, 2009 at 20:51:27:

I don't know how cost effective it is but here's the story I found on a local dairy farm.

Vander Haak Dairy
The Vander Haak Dairy is a family run farm operating in Lynden, Washington since
1968. It became the first dairy in Washington State to install a commercial anaerobic
digester. The system utilizes a patented plug flow digester, designed by GHD
Incorporated of Wisconsin, that handles manure from three dairies and up to 1500 dairy
cows (as currently configured). In general, plug-flow digesters have few moving parts
and work well with dairies, like Vander Haak, that collect cow manure by scraping
instead of flushing the manure with water. The unprocessed manure is collected in a
receiving pit and pumped directly into the anaerobic digester vessel where it undergoes a
two-stage digestion process. In the first stage, raw manure is mixed and heated to 1000F,
using the reclaimed waste heat from the engine/generator set. This facilitates the growth
of acid forming bacteria that breaks down the raw manure into simpler volatile fatty acids
and acetic acid. The slurry then gravity feeds into the second stage of the digester where
methanogenic bacteria convert the volatile fatty acids into biogas. The second stage of the
digester process takes about 20 days, after which the remaining materials flow into an
effluent collection pit where they are further processed. The dairy is currently assessing
the impact of other available feedstocks on the system processes.
The biogas generated in the digester is collected and burned in a natural gas fueled
reciprocating engine set modified to burn biogas. Waste heat from the engine set is
5
recovered and used to heat the digesters (30 to 60 percent is used), and could potentially
be used in the future to provide for other thermal needs at the dairy. The engine genset
produces about 285 net kW of electricity (parasitic load is 15 kW) which is sold to the
power grid. This is enough electricity to serve approximately 180 average homes. The
remaining digester effluent is separated into a solid and liquid stream for further
processing. The separated solids are currently processed into bedding materials for the
dairy or sold to other dairies for bedding. Additional work is underway to develop this
material into a compost or soil amendment suitable for sale to commercial nurseries as a
replacement to peat moss. The liquid stream from the digester is used as a high-value
fertilizer, rich in phosphorous and useable nitrogen.

Replies:

Add a Reply Name: E-Mail: Subject: Comments: Optional Link URL: Link Title: Optional Image URL: Optional Video Title: Optional Video URL: Advanced Posting Options Email Notification: If you check this box, email will be sent to you whenever someone replies to this message. Your email address must be entered above to receive notification. This notification will be cancelled automatically after 2 weeks.   Advanced Posting Tools   Upload Photo  Select Gallery Photo  Attach Serial # List  Return to Post

TRACTOR PARTS	TRACTOR MANUALS

We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]