[USCC] ammonia from Fish compost

[Will Brinton]

Gregory

We have been running whole salmon mortalities and aquaculture residue 
composting here recently at fisheries in Maine, and generally assisting 
in composting fish wastes, dating from 1985,  in coordination with the 
Maine Aquaculture Association (Hallowell Maine)

It is very typical of fish composting that the protein-N fraction breaks 
down and releases ammonia far more rapidly than the
carbon fraction can be metabolized by microbes in order to absorb N in 
accordance to their cellular needs of about 12 carbons to one nitrogen.
The rate limiting factor is not so much the nitrogen excess but the 
temporary unavailability of the carbon. You could say that one process 
is chemical and the other biological and that the two are not 
necessarily well coordinated, plus heat intensifies the discordance of 
the chemistries.

Two approaches exist: one is to feed the proteinaceous ingredient more 
slowly (rather than using more carbon per se) which means multiple
additions slowly over days. The other is to use carbon sources that are 
more available, or more naturally absorbent.

In the first USA  manual for composting fish waste published by Woods 
End and the Time & Tide Resource Conservation District (1988)
and the subsequent manual on scallop composting published by Florida Sea 
Grant College and Woods End (1992) the matter of control  of ammonia 
losses, ammonia odor and the CN issues were discussed at length. We 
found  that the ammonia sensory threshold was exceeded as soon as the pH 
of the compost exceed from 8.2 on the low end to 8.8, depending on total 
ammonium content. So if you are smelling it, chances are your pH is now 
somewhere over  8.2, which is quite high. That leads to the third option 
which is reducing pH by addition of peat moss (natural) or 
gypsum+super-phosphate (chemical).

William F Brinton jr President
Woods End Laboratories, Inc.


gregory th stamler wrote:

>Good day.I am in charge of monitoring our aerated/in bag composting of 
>fish offal combined with wood shavings. After a day of starting the 
>air, the temp. gets to 60 C and a vapor cloud with a strong ammonia 
>smell starts coming out of the open toped bag.
>I have two questions: Is the nitrogen  portion of the mix too high 
>(which I think is)  and should I cover the top of the bag more to 
>condense the vapor back into the bag and make the ammonia available to 
>the critters doing the work !!
>As always your thoughts and questions are welcome. Thanks, Greg at 
>Meeker Aquaculture.
>  
>