Subject: Blood Meal and Compost
HK> One of my compost piles is mostly dead grass, leaves, and
HK> weeds. It was going pretty good but then after a month or
HK> so, it just lost its oomph (sp?).
A good batch of compost is *supposed* to lose its "oomph" after
about a month or so. It is not like a campfire where the wood
oxidizes down to ash in a short time. Biological oxidation is
determined by the fate of microbes; not a chemical formula.
Raw organic matter has both volatile and non-volatile solids.
The non- volatile fraction includes ash, minerals, glass,
rocks, metals, and other non degradable components. Even a rich
organic matter source like peat might contain 10% to 20% inert
matter. Many manures may be as low as 50% organic matter,
especially if they are scraped off soils.
The composting process is considered "complete" if there has
been a 40% volatile solids reduction. When about 20% has been
reduced, it is increasingly difficult for the pile to generate
heat, since most of the "volatile" fuel has already been
oxidized. Of the organic (volatile) solids, much is in the form
of lignin and cellulose (wood). This fraction, while organic,
is not as "volatile" biologically speaking as are
carbohydrates, sugars, and proteins which decompose quickly.
These materials take longer to decompose biologically, so may
be why your pile has "slowed down".
On top of these complex interactions between microbes, fungi,
actinomycedes and organic raw materials, the byproducts of
decomposition, particularly humic compounds, are in and of
themselves slow to decompose and oxidize. Humus, the most
stable form of organic matter in the soil, may last for years
and years without further breakdown.
So adding fresh matter like blood meal may cause a sudden burst
of decomposition activity, sort of like adding lighter fluid to
cool charcoal briquettes, but don't expect the rest of the
matter to suddenly spring into ignition and decompose.
My rule of thumb, if you truly desire active, hot compost, is
to make piles in batches, mixing and moistening thoroughly
*before* putting the stuff into a bin. Then let the pile cook
for three or so weeks, maybe with a turning or two. Hot
composting is also helped by passive aeration from the base,
rather than the sides.
For a pile that seems to have cooled prematurely, mix 50% with
fresh green material like grass clippings to get it to re-cook.
I believe that you will find this plan more effective than
dosing it with blood meal.
HK>Anyway, I figured that it was lacking nutrients so I
>sprinkled a half cup or more of blood meal in there. What do
>you think? Will it help? Oh yeah, my compost bins are of the
>poor man variety (a chickewire cylinder). Actually, them work
>remarkably well. They take a little longer than the wood or
>plastic boxes, but with my limited amount of plant refuse,
>they are perfect. Regards, Howard Knight
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