HOW LONG DOES IT TAKE TO MAKE COMPOST?
from three months to three years!
Composting goes through 2 stages - a hot and a cool one.
How long it takes
What kind of home compost bin you have
What materials you put in
Where you place your bin
How moist and airy your bin is
How much trouble you have taken
What grade of compost you want to use
If you are not sure take a look to find out if
it is ready because
weather and temperature make a big difference: during a clean up of
rubbish dropped on high Scottish mountains (Munros) volunteers found
banana skins that were 2 years old! Given some warmth they would
have rotted down in three months.
more care you take, the quicker you will get good compost. but you
can hurl everything into your compost bin and three years later
there will be usable compost at the bottom.
So how do you decide which approach is right for you?
The hotter the bin the faster the composting process.
A covered, plastic bin in a sunny place could get up to 60C in the
summer and if you fill it with quick
rotters, leave the contents to decompose without adding fresh
material, and turn it once or twice, you may
have usable compost after 3 months.
This will be mulching compost - roughish stuff useful for:
putting round shrubs and bushes
putting at the bottom of a planting hole
but too coarse for potting or seed sowing.
If you want to use your compost bin continuously, adding
stuff every day or every week, then you cannot
turn it as this will mix up the fresh and partially decomposed
materials. In this case make sure that you put in a well balanced
mix of compostables and after 3 months there may, in ideal weather,
be a little finished compost at the bottom.
However, it is probably easier to wait for 6 months, over the
summer, and then harvest some compost. When you are filling your
compost bin over the winter, the material is breaking down slowly,
because of the cold, so what you put in in the autumn wonít be ready
for use until late the following summer.
Larger bins generate more heat and retain it better so work faster
than little bins. If you have a small bin it is especially important
to put it somewhere it will get some sun or you will be waiting a
couple of years for your compost to be ready.
Turning the contents of your compost bin helps to:
generate heat as it introduces air to the middle of the heap, air
needed by the bacteria doing the composting for you. The more often
you turn the heap the faster it will work. The downside is that it
is hard work and that you have to have another bin for your fresh
compostables while the first is rotting down.
Wooden bins do not retain heat as well as plastic and they often dry
out round the edges in hot weather. Dry materials do not break down
as those bacteria will only work well on moist stuff. The classic
New Zealand box works on a 2 year rotation: fill one side one year,
leave for a year while you fill the second side and dig out the
finished compost in the spring of the 3rd year.
WASTE THAT SHOULD ROT DOWN QUICKLY, THAT IS IN ABOUT 6 MONTHS:
Annual weeds - chickweed, groundsel,
bittercress; include the roots because the soil sticking to them
contains lots of useful bacteria
Dead flower heads with thin stems like
sweet peas, stems as thick as delphiniums may take a year to
completely break down
Fruit peel rots quickly, put orange and
lemon peel into a compost bin, it is only the worms in a wormery
that do not like it.
Vegetable trimmings like tattie
peelings, pea pods and outside leaves break down fast.
Lawn mowings that have not been treated
with herbicides break down fast as long as you add no more than 20cm
depth at a time. If you have more, layer them with drier, more
absorbent material like weeds and stems. (See Too Much Grass for
Vegetable plants and leaves like
rhubarb leaves, tattie shaws, bean plants and carrot tops
Tough material like cabbage and sprout stems take years.
Peach stones and avocado stones last for years in a compost heap
WASTE THAT USUALLY TAKES 1 TO 2 YEARS TO ROT DOWN:
Stems of herbaceous plants that you cut back in the autumn
Soft, green, hedge clippings and prunings; but
conifer and other evergreen cuttings will take 3 years or more to
completely break down
Nettle and dock stems
Paper and cardboard
Shredded woody prunings
Autumn leaves But
oak and beech leaves may take 3 years
WASTE THAT WILL PROBABLY TAKE 3 YEARS OR MORE TO ROT DOWN:
Softwood sawdust and wood shavings
Ivy and clematis stems
Holly and other evergreen leaves or conifer needles
Woody twigs that have not been shredded
Egg shells, essential to counteract acidity in the heap but slow to
Moss in large quantities ie more than a small bucket full
A compost bin full of grass clippings with nothing else layered
The larger the bits you put in the longer they will take to
A small amount, eg 10%, of slow rotters mixed in to a heap
largely composed of quick rotters will disappear but, in general,
slow rotters will rot slowly whatever else is in the compost bin.
You will be picking twigs out of your otherwise finished compost if
you mix woody stuff into a quick bin.
Donít despair if your compost isnít ready to use, leave it a bit
longer and, in the meantime, get another home compost bin for your
fresh compostables or bag up the semi-rotted compost and use your
bin for fresh material.
If you have a small garden and are short of space it is worth trying
to make compost as quickly as possible, plenty of heat, a good
balance of materials and some turning, so that you can manage with
just the one bin.
If you have a large garden you can take the lazy approach and have a
row of bins all composting at different rates.
The best compost cannot be produced overnight Ė it takes time.
For estimate of how long long different materials take to rot down