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2012-05-18 11:05:24

Composting is a natural process whereby organic matter is broken down, enabling the nutrients in it to be returned to the soil. Think of the mulch on a forest floor: leaves, twigs and branches from the trees combined with the remains of the insects, birds and animals that fed on those trees. Various decomposition processes gradually break the mulch down into finer and finer pieces, releasing all the nutrients required to make it in the first place. This is how nature recycles itself.


That same process can be harnessed to turn weeds and waste into natural fertiliser. The simplest way of doing this is to pile everything on a heap and allowing it to digest itself. This happens through the beneficial action of worms, insects and bacteria. The worms and insects eat their way through the waste, excreting it in a refined from. The bacteria go to work on the complex organic compounds and break them down into simple nutrients.

The process can be helped along by human action in three ways. Firstly, by ensuring that a balanced mix of green (leaves and grass) and brown (twigs, stems and chipped wood) goes in. During decomposition, the green releases nitrogen and the brown absorbs it, so starting with a balanced mix ensures that you will end up with a balanced compost. The browns also decompose incompletely, resulting in a compost with plenty of organic matter, helping aerate the soil and assisting in the retention and slow release of moisture. Secondly, by keeping the compost moist, but not wet. This creates an ideal environment for the composting agents to do the good work. Thirdly, by regularly turning the heap. This keeps the heap loose and aerated, again creating an ideal environment for the composting agents, as well as spreading them evenly through the heap so they can compost everything.

The composting process gives off heat, helping to kill any seeds in the mix and also destroying all but the most tenacious diseases. The heating process also creates an ideal environment for the more effective kinds of composting bacteria that do not work well at lower temperatures.


Adding compost to one of the gardens on the farm.A more advanced method is vermi-composting. This involves feeding a colony of earth-worms with a selection of organic matter. They eat the waste and excrete a very concentrated nutrient solution called vermi-tea (that actually looks more like coffee to me, but who am I to judge?). As worms have a tendency to wander off into the soil, it helps keeping them contained. We use an old water-tank that was damaged by a fallen tree during a wind-storm. An improvised lid keeps the worms dark and safe from predation by our ample population of birds. The outlet at the base of the tank is handy for harvesting the vermi-tea, which we introduce to the soil through our irrigation system.


The last composting method we use is Bokashi. This process relies on a bacteria-colony that loosely resembles the bacteria in our digestive system. We run our Bokashi-digesters in tanks rated for chemical applications. The bacteria is introduced in a dried mixture comprising of fermented milk made with a rice-water starter, held in a matrix of bran with some molasses added to feed the bacteria in their initial growth-phase. The chief advantage of Bokashi is that it can digest everything we can, and then some. For feed-stock, we use kitchen waste (including cooked starch and meat, dairy products, fat and oil), garden waste and dog-shit (we have a pair of Great Danes, so dog-shit management is of paramount importance...). The process eats up almost all the solid matter and yields a virtually odourless liquid fertiliser very similar to vermi-tea that is tapped off and goes straight into the irrigation system.


We also employ the Bokashi-method in our septic tanks and bio-digesters for treatment of sewage, as it digests all the sludge that settle at the bottom of the tanks and would appear to neutralise all disease-causing bacteria in sewage pretty effectively, yielding safe, nutrient-rich water as the result.

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