[Digestion] Digestion Digest, Vol 5, Issue 10

[finstein at envsci.rutgers.edu]

All,

Re: CSTR at Beltsville

Historically, CSTR was designed based on aerobic thinking before it was
understood that the microbiology of aerobic and anaerobic (methanogenic)
systems are entirely different. It is now understood that to realize
maximal rates of treatment one must preserve the integrity of microbial
associations rather than smash them apart - as in CSTR. I'd include here
the URL to a brief publication summarizing a rather involved - but very
well established - story, but believe such inclusions get weeded out by
the list serve. You may contact me if interested.

The best to All,

Mel Finstein


Melvin S. Finstein, Ph.D.
Professor Emeritus of Environmental Science
 Rutgers, the State University of New Jersey

105 Carmel Road
Wheeling, WV 26003
(304) 242-0341
Email: finstein at envsci.rutgers.edu

>
>
>   On 13 Jan 2011, at 17:16, <armoss at umd.edu>un wrote:
>
>     Charles-
>     There's at least one small-scale digester of that size currently
> operating in the U.S. - at the USDA Beltsville Agricultural Research
> Center in Beltsville, MD.  The dairy's herd size is roughly 125-130,
> with ~100 milking and producing manure at any given time (dry cattle
> are let out to pasture).  The digester was built in 1994 and was
> constructed as a continuous stirred-tank reactor.  I have tentative
> plans to conduct research on this digester simultaneously with a
> low-cost, pilot-scale digester project operating on the same
> waste-stream that's being constructed by our lab group at the
> University of Maryland.  I don't have intimate knowledge of the USDA
> CSTR's history, but I can tell you what I know.
>
>     The digester was originally constructed for odor control as an
> upright, cylindrical concrete tank (I'm not sure enough of the
> designed HRT to give you information on it), and was later insulated
> with gunnite-coated styrofoam.  It operates on mechanically
> screw-press separated, scraped waste, and utilizes the biogas produced
> to power a boiler that circulates hot water through a conveyance
> system installed within the digester for heating;  a combined heat and
> power electric generator was installed in the mid-2000s, but it has
> never been brought online.  The digester's had a number of problems
> come up, including repeated clogging of the supply lines (originally
> 3-4" ID, now 6"), the break down of the screw-press separator and
> supply pumps, and the corrosion of the boiler due to inadequate
> scrubbing.  To be fair, many of the problems associated with the
> digester are the result of fluctuating research interest, funds,
> management, and the lack of an effective biogas scrubbing system, but
> they exist all the same.  Currently, the digester is up and
> operating... although obviously not ideally.
>
>     Although most of the digestion systems are covered lagoons, the AgSTAR
> website contains a link to a Excel file detailing the digesters
> currently registered in the EPA's system (look under "Farm Project
> Profiles").  A few of them approximate the herd numbers you're
> interested in.
>
>     As a side note, our research at the University of Maryland, together
> with research at Ohio State and the University of Wisconsin, is
> attempting to introduce smaller-scale, lower-cost systems in the U.S.
> I gave a presentation in October on small-scale digestion and some of
> the current efforts that you can find here.
>
>     Good luck hunting!
>
>     -Andy
>
> Andrew R. MossSustainable Agriculture Research & Education
> FellowUniversity of Maryland Dept. of Environmental Science and
> Technology1445 Animal Sci./Ag. Engineering (Bldg. 142)University of
> Maryland, College Park, MD 20742Phone:  (865) 363-5535