Compost Making FAQ - Part 3
Subject: Composting grass
WT>Has anyone had a good experience with composting grass
>When I put it in my compost pile it turns into a sticky mess
which takes ages to decompose. I wonder if there is something
the grass could be mixed with to help the breakdown process or
should I join my neighbours in the weekly routine of hauling
bags of the stuff to the curb? Help, help, I'm drowning in hay!
I have composted literally hundreds of thousands of tons of
grass clippings, and bag my grass at home too. I believe that
composting clippings and applying compost to the lawn is better
than letting the clippings lie. (although mulching the
clippings is better than landfilling any day!)
My recipe is the same for home and commercial alike. I have
two active batches going and one curing pile. Each week, I
stockpile the clippings in a holding bin. The next week, I add
the current week's clippings with last week's along with some
old compost (10% up to 50%) which is coarse with old wood chips.
These materials are layered OUTSIDE the active bin, watered
layer by layer. THEN they are forked into the active bin,
mixing thoroughly, watering dry areas. My active bin has an
aeration mat at the base allowing air to infiltrate from the
base. Once the bin is full, since I make *batches* of compost,
I "poke" the pile from the top to the base with a steel rod
every six inches to help it breathe.
Two weeks later, I take half of the older pile and put it into
the curing pile with half going into the new batch as the
compost inoculant. Once the material in the curing pile is
dark and crumbly, I screen it and use the oversize material as
a bulking material. Occasionally I add wood chips to help keep
the pile loose. I never turn the pile, but splitting it in
half to make old and new is a kind of turning. The piles are
always sweet smelling.
* May 23rd - Please let me know if you did not receive this.
D>I would have to agree with the low yield from table scraps,
vegetable peelings, coffee/tea wastes.
I must have missed the first part of the post. Are you talking
about low volume (total amount of compost) or the low nitrogen
value of compost in general, or compost from these ingredients?
Let me try to answer all three questions. The volume of
finished compost is typically 1/3 of the original volume, more
if there is free air space in the original mass. Brush shreds
down to about one tenth the original mass, for example. Mass
reduction is another matter. Net dry weight loss is typically
one third. This is actual nitrogen and carbon conversion to
ammonia, heat, and CO2. Most weight loss is from moisture
reduction from 80% moisture original matter such as wet grass
clippings or fresh garden scraps down to 40% moisture compost.
As far as fertilizer values, I have yet to make a true compost
that is over 2% nitrogen. Sure, I can have unstable compost
which is higher, but a cured compost will not be over 2% due to
the inherent biological restraints of the carbon to nitrogen
equation which is essential for proper decomposition. Higher
carbon ratios will result in lower net nitrogen values. Higher
nitrogen in the original feedstock will result in the release
of air borne ammonia and other nitrogen compounds and water
borne nitrates and nitrites.
Compost N values are stable so the can automatically be doubled
when compared to chemical nitrogen values, of which 50% or more
is lost in the first 24 hours of application. Compost N values
also have an accumulated fertility quotient, of which 60% is
available the first year, 20% the second, 10% the third, 5% the
fourth, and so forth. Chemical N has no accumulated value.
As far as the low volume of incoming table scraps as compared
to the net demand of they typical yard, I can state with
certainty that even if you bag and compost all of your yard
trimmings, leaves, and table scraps, your organic matter demand
for the yard is still greater. I recommend 1/4" of compost as
a top dressing PLUS letting the clippings lie in order to keep
a lawn organically sustainable. If you are trying to increase
the lawn's humus content, that requires an additional 1/4 inch
to make the soil richer.
One quarter inch of compost is one cubic yard spread over 1232
square feet. The typical lawn at 3,500 square feet requires
three cubic yards to be sustainable (with letting the clippings
lie) and twice that amount to build the soil up, usually
applied as a top dressing in the spring and fall. If a person
was improving the soil *before* the sod goes in, then 32 cubic
yards spread 3" deep would be called for.
You can see why I believe that it is important to support
municipal composting, as the single homestead is hardly capable
of generating sufficient compost to keep up.
As far as recommending good small composters, I recommend any
of the small, plastic, enclosed bins such as the Earth Machine
or Green Genie. I recommend round ones over square ones as
square bins have cool corners. Table scrap bins should be
covered to inhibit rodents and should not have too many
openings on the side. I do not recommend open air designs for
passive, table scrap bins as they let in too much air, dry out,
and let in vermin.
Pay no attention to the supposed door underneath to take
compost out. They are hard to use and compost does not "flow"
so well. Use instead bins which act like "jello molds" which
can be lifted off when full and the composting process started
new in a different spot. The old pile keeps its shape and will
cure just fine in the open air. Remember to use some old
compost mixed in with the fresh table scraps. This inoculates
it with active bacterial cultures and helps cover it from flies
For the best home composter, I recommend indoor redworm boxes.
Check out Mary Appelhof's book "Worms Eat My Garbage" for tips
for the budding vermiculturist.
* April 9th - Man, that lightning sounds clo#A#v!&^#v?##vNO