Stage one – getting warm
Microorganisms will thrive
when you create the ideal conditions.
Bacterial populations can double every hour and so within a very short
space of time the heap starts to warm up. Different types of bacteria operate
at different temperatures, generally the hotter compost gets the faster it
breaks down – but even at low temperatures there will be bacteria actively working.
The low temperature bacteria (sychrophiles), give way to warm temperature
bacteria (mesophiles), these operate between 20 – 30 degrees C
Many small compost bins never
get to the really hot temperatures described below in the next stage and that’s
fine as the low and mid temperature bacteria and all the other micro and macro
organisms will do the job, it will just take a little longer.
Stage two – getting hot
A freshly made heap can get up to 60 degrees Celsius or more within 24 hours. What you have done is ignite a bacterial bonfire that, as long as there is sufficient moisture and air, will continue to ‘burn’. The warm temperature bacteria are in turn overtaken by the higher temperature bacteria (thermophiles), which operate between 40 – 70 degrees C. This is seriously hot and if you have built the heap to keep the air flowing and the heap doesn’t choke up, then, like a well-built fire, the heap will compost rapidly.
This is where a tumbling compost bin is especially useful because, as long as you have added wood chippings (or something structural) a quick turn will make sure the air will reach all parts of the mass of material.
However, don’t be concerned
if your compost doesn’t get to these high temperatures. The advantage of creating high temperatures is that it cooks weed seeds and all the nasty human and plant pathogens in a very short space of time. This is important for commercial composting businesses that need to sell a quality product and useful for anybody wanting to produce, particularly weed seed free compost too. [AC4] [OU5]
On a small scale it’s more
difficult to maintain high temperatures but a well made heap in the low to mid
40’s is pretty hot and over time will do the same work as the high temperature
heaps. Hot heaps need
turning as much to cool them down as to get more oxygen in they can actually go
up in flames and even if they don’t, prolonged high temperature can result in a
product which more closely resembles charcoal, than compost.
At the high temperatures the
mid and low temperature bacteria just switch off but they wake up when the
temperature drops again.
This hot stage of composting
can take as little as two weeks, given optimum conditions.
Stage three – cooling down
The temperature will gradually
drop off and no amount of turning will induce it to reheat. The heap will be
reinvaded by the lower and mid temperature bacteria and fungi and this stage
will merge almost imperceptibly into the final stage.
This is the time to leave
your heap alone, don’t turn it anymore, if you have a tumbler, empty the
contents into a pile or bin, cover it to stop the rain getting in, and let it
quietly mature like a fine wine.
Stage four - maturation
Maturation is the part of composting that cannot be hurried. The chunky woody bits that were so useful at providing airways to help compost the soft green wet materials will take a long time to be broken down, primarily by the fungi and creatures like woodlice that will eat the wood. Worms also move in at this stage and are invaluable, especially at converting the heavier denser materials into wonderful compost.
Since big chunky woodchip can
take years to break down, you can sieve your compost after six months to a
year, when you want to harvest the compost for use, or when you are
transferring from a tumbling system into a maturation system, reusing the
chunky parts with your new fresh material
Full details in Nicky
Scott's book pub Sept 24th 2009 'How to make and use compost - in spaces big
and small'
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http://www.greenbooks.co.uk//store/product_info.php?products_id=322
