[Digestion] gasyield indigenious cowdung

Amy and Jim Rankin ajrankin at hughes.net
Mon Oct 25 13:32:05 PDT 2010

> 540 M3 from 1000 Kg of cow dung ?
> Is it possible that  there is an error in measurement ? OR an enthusiastic
> overstatement  by the gentleman ?
> ( If cow dung or the flora present in /alongwith it had so much of energy
> value ,,,, it would create so many possibilities )

While I have nothing to compare that value to, I assume that this is a 
"batch" process digester, has a very long retention time and very likely has 
only a small amount of water included to maximise the digestable content of 
the system.  It is unlikely that the gas yield can be compared to 
continuously fed - flow through digesters (which usually have higher water 
content requirements and become economically prohibitive to build for 
comparable retention times).  In other words, completely the opposite of the 
sugar/highly digestable substrate type digester Dr Karve deals with and very 
different from most other digesters as well.

Our experience with a highly and rapidly digestable substrate,  cheese whey, 
shows the expected tendency to rapicly acidify and pickle the digester if 
the loading rate is increased rapidly.  The best solution at hand seems to 
be reinnoculation with cattle manure slurry at regular intervals as well as 
maintenance of a minimal feed rate in the off season as much as possible to 
avoid starting from zero when the cheese plant opens up full capacity in the 
winter time. The rate of operation in the off season is not strictly 
profitable, but is being tried this year for several reasons including 
maintenance of the digester function.

We have some experience using cheese whey as fertilizer and have never seen 
any great benefit to the grass it was applied to beyond the small 
protein/Nitrogen content.  Perhaps the level of salt ( NaCl ) included has 
some inhibitory effect on the soil microbes and prevent their rapid growth 
or perhaps the compaction caused by the trucks applying the whey was a 
problem.  In some instances the grass was burned by the application of the 
whey and took some time to recover, so any or all of these could be 
confusing factors that prevent seeing the result of the lactose sugar 


James R Rankin, DVM
Cedarcrest Farms, Inc
Faunsdale, Alabama USA 

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