Updated: Dec 1, 2020
This composting workshop was held at the Kaitāia Community House Garden on Puckey Ave.
Composting is not done by people, it is done by smaller organisms such as bacteria, fungi, worms,and other small critters. It is these organisms in the pile that interact with the materials and do the composting work. Our job is to provide the right mix of materials to create the right environment for the micro-organisms and other small critters we want to encourage in the pile.
A compost pile goes through a natural life-cycle which involves different organisms at different points of the process.
Composting is not necessarily complicated once one understands the fundamental principles.
Composting requires the right amount of carbon, nitrogen, air, water, temperature, and time. When it comes to adding carbon and nitrogen, we are never adding pure carbon, or pure nitrogen. Everything we add to a compost pile has its own ratios of these. As I'm not interested in spending my time focusing on counting the ratios in each thing I add to the pile, I look at it in a different way. Carbon creates structure in living organisms… plants and animals. The more rigid and strong something is, the more carbon content it has. A tree trunk is rich in carbon, and so is a diamond, and an egg shell. In the garden, the stalks of annual plants are a readily bio-degradable form of carbon.
Right now in late spring, our garden is full of wonderful carbon-rich stalks produced by our annual plants going to seed. We have artichoke, radishes, celery, and brassicas such as mustard, broccoli, kale, and cabbage. Sunflowers, fennel, broad beans, Jerusalem artichoke, corn, and others are also great carbon-rich additions to a compost pile. We harvested some seed to save and chopped up the rest of the plants to add to the pile. The stalks are not only a good source of carbon, they also create air-spaces in the pile, thus helping it to stay aerobic, which I will explain about in a moment.
Other readily available sources of carbon-rich materials one can add to the compost include shredded paper, ripped up cardboard, sawdust or fine wood chip, etc.
Nitrogen content is higher in soft materials such as little weeds or fruit and vegetables. Nitrogen rich materials don't have the same strong structure that carbon rich materials have. Egg white is rich in nitrogen, as is chicken poo. Kitchen scraps are generally considered to be a nitrogen source for the compost, along with animal manures, coffee grounds, fresh lawn clippings, and the like.
Too much nitrogen in the pile will result in a bad smell. So will too much water.
If the compost smells bad, its an excellent indicator that something is not right. Generally, this is because the compost has gone anaerobic, meaning it is lacking oxygen.
The compost needs air. This is because the bacteria that do the composting require air to live. They are called aerobic bacteria. Chopped up stalks create air gaps in the pile helping to create an aerobic environment. Too much water in the pile reduces the presence of air, therefore, if you have a sodden pile, you are not creating the right environment for the bacteria that do the composting. It’s a little more complicated than this, as in fact the pile goes through aerobic and anaerobic cycles, but what is important, is for you to know that your task is to make sure your pile is not drowning in too much water.
That said, the pile needs water, because water supports life, and the micro-organisms in the pile need water to live. If the pile is too dry, the micro-organisms will not thrive.
Temperature is not something we add. It is created by the breakdown process facilitated by the bacteria. If we give the pile the right conditions, heat will be generated, aiding the decomposition of all materials, including pathogens and seeds. Building a pile to a specific size will mean it will insulate itself better, maintaining its heat. 1.2m sq. is a good size. A wooden box will also help insulate the pile.
If the compost is too hot, which can happen if there is too much nitrogen in the pile, adding carbon rich materials can reduce the heat and slow down the process. If the pile is too hot, nutrients are lost. Opening the pile up or turning it can also reduce the heat, however, I tend to avoid turning the pile often, so as not to interrupt the communities of micro-organisms that form. Turing the pile introduces oxygen which will speed up the composting process, though as far as I have read, speeding up the process also reduces the carbon content of the end result. A high carbon content in a finished compost stabilises the nutrients so they are less water soluble and therefore less likely to wash away. This means the compost added to the garden will provide longer term, slow release nutrition for your plants, and hold more moisture, saving you water and mitigating the affects of drought.
If your pile is too cold, adding nitrogen rich materials will encourage it to heat it up. A cold pile can result from too much water, and also, not enough water.
A compost thermometer may be a fun thing to invest in, in order to get intimate information about your pile. Alternatively, putting your hand in to feel the temp will let you know how its going.
The natural cycle of a compost heap involves different bacteria that thrive at different temperatures throughout the composting process. In the cooling down phase as the compost matures, fungi, worms, and other organisms will move in to do their part.
And so to the last requirement of composting. Time.
Very quickly made compost (a few weeks) is possible with regular turning, although, as I
mentioned above, this will affect the quality of the end result. I prefer to let nature take its course with minor intervention on my part, in the hope that I will have a more stable, higher quality compost as a result. I prefer to let my compost mature over 3 to 6 months.
I am no compost expert. My mother was a fabulous gardener and I grew up with a fine role model in composting. I have composted and made gardens everywhere I have lived in my life. I am excited to have been offered a job composting in 2021 and look forward to learning so much more and sharing what I learn.
The photos shown are of a recent workshop we held in building rat proof compost bins out of pallets.
Jo Picolo Community Garden Co-ordinator.