Composting 27th Febuary 2007
We constructed Four Compost piles to experiment with how the different variables manifested around the environment and what the effect was on the process. Also to gain experience and a feel for the art.
There are four important factors that determine the quality of compost.
Moisture; The ideal level is saturated and well drained.
Compostion; The carbon/nitrogen ratio 25:1 is the optimum level for organic life.
Particle size; Maximising edge will mean maximum efficiency in the breakdown. It is important to use enough bulk to allow airflow.
Pile size; Big enough to insulate, small enough to allow oxygen. A cubic metre is the optimum.
Thermophilic batch pile
This was made in the compost chamber, a tried and tested formula was used.
We harvested several activators: tanzi, and another green leafy from around the bamboo. Azola, a red floater from the dam.
Blood + bone for nitrogen and mineral nutrients.
A slurry of fresh cow manure mixed with water.
Dry grass slashed by the tractor.
Once we had all the ingredients assembled; a team was organised.
Each layer was assembled with a fairly even distribution.
Water was added as we went until it ran from the bottom. We rotated until some twenty layers were heaped up and the pile was about a cubic metre.
It was observed that the last 30 centimetres seemed to compact the pile. Making final progress appear slow.
As freshly cut grass is almost the perfect balance of the composting factors a pile of this was made alone. It is worth noting that due to logistics and lunch the grass was allowed to sit for several hours after it was cut before it was collected and piled. During this time the nitrogen can evaporate and escape the system.
Fine particle pile
This pile took the most work, many more hours than the rest. It was the most physical and done during the peak sun of the day. Yang yang (?? Someone please enlighten me on the actual name), banana stalks, native tobacco and a few other green crops were pushed through a chaff cutter (made in late 1800!). This reduced them to a very fine green mulch. This alone would probably go anaerobic so it was blended through some dry cut grass.
This woody pile was made from fallen needles from the Casherina trees and piled up with alternating layers of arrowroot broadleaves.
Although there is a lot of space for air to pass through the pile, the arrowroot leaves were whole with not a great deal of surface area for the magic microbes and bacteria to eat.
However the biggest factor in this pile is that it is very carbon rich and nitrogen poor not making the ideal conditions for them to thrive. It is very unlikely this pile will fire up and compost. It is more likely to moulder, a process that will break it down but over a much longer period of time.
Jargon: Hygroscopic – If the material is allowed to fully dry it does not want to absorb any moisture.
Thermophilic – These are the high temperature loving bacteria that really do the work on the breakdown. They are capable of reducing seeds, harmful bacteria or viruses and many other things to the base nutrients in humus. They can thrive in temperatures from 50-70 degrees C.
Anaerobic – These organisms do not require oxygen.
Supplementary Notes: Plants can thrive when they have the ideal balance of nutrients, moisture, sunlight and love all blended harmoniously in the magical medium of soil.
In conventional farming the essential nutrients are made water soluble from oil derivatives, this external source of nutrients is purchased by the farmer. These additives have the potential to be mismanaged and disrupt the delicate balance of natural systems as they are not integrated into healthy living soil like compost.
It does take work to concentrate nutrients. Cows, pigs, goats, chooks and worms naturally do this work through their digestion and deliver us this concentration. This makes them quite valuable resources on the integrated organic farm.
A common mistake in urban garden composting – The compost receives only vegetable scraps – they are large, wet and nitrogen rich. Without a bulking agent like straw or wood shavings the pile heaps and doesn’t get either the balance or oxygen it needs and the heap will begin anaerobic decomposition Ã¢â‚¬â€œ characterised by an unpleasant smell and less viable end product.
TWO WEEKS LATER UPDATE:
I visited the piles we made two weeks later to see how they were doing.
First up; the grass pile. As predicted the pile was too dry and lacking in nitrogen by the time we got it together. It looks more like mulch than compost.
The second pile was the fine particles.
It went off, too much infact. The pile was 1/5th its original size and had definately broken down into a compost – but it also burnt itself out. If the pile had been turned a few days after building it, we could have kept the reaction going and composted more of the outer edge.
The last pile was the rough stack. It fell somewhere in the middle, inside there was evidence of mould. It will take a while for it to break down this way.
Adding more water, activators and continuing to turn it will speed up the process.