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Composting

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Composting

by Megan Macpherson

Composting is a great way to recycle garden waste and organic matter. It reduces the amount of waste at garbage dumps, which in turn reduces the amount of greenhouse gas emissions that emanate from landfill. There are a few things to learn about composting before you begin, as it's not as easy as just dumping everything from your bin into the compost. Successful composting is a delicate balance of nitrogen and carbon. Sounds complicated? It's not really, once you know what to put in and what to leave out, and it's an easy way to produce rich mulch for your garden, as well as recycle waste.

Composting works by speeding up the natural decomposition process of waste and garden refuse. Micro-organisms such as fungi, protozoa and bacteria break down waste within a composting bin or heap. Hot, aerated compost creates heat, carbon dioxide and water. This is opposed to an anaerobic (without air) landfill situation which produces the greenhouse gas methane.

The ratio of carbon to nitrogen is 20-30:1. It is best explained in terms of browns and greens. Brown (carbon) materials; such as paper, cardboard, sawdust, woody garden refuse, and green (nitrogen) materials; as weeds, food scraps, and soft garden refuse. The balance of these components is the key to good compost. Water is another element, and the compost should be kept moist for the micro-organisms, but not too wet.

What can you put in your compost? Well, it is probably easier to say what not to put in, such as meat, fish, chicken, dairy products, cooking oils, plastics, metals, food wrappers, diseased plants, fly blown fruit, pet droppings, and treated wood products. What is good for the compost is all other kitchen scraps, tea bags, coffee grounds, weeds, both dry and green garden refuse, newspaper, cardboard- just to name a few. Keep the nitrogen/carbon ratio in mind, as well as water, and any problems with the compost can be solved. For example if the compost is too wet, add more brown material, if too dry add more green material or water. If it is a material that will kill bacteria such as pesticide treated plants, or salty or oily food scraps, then dont put it in the compost. If it is a material that will decompose, then put it in. Air is the last element, to make the compost a fast and aerobic process. A compost heap should be turned regularly, and a compost bin should have holes drilled in the side covered with mesh or should be able to be turned.

Worms can also help with the decomposition process, and a compost bin that sits on the ground will encourage worms to venture in from the earth. Worms break down organic waste by consuming it and turning it into castings, which can be used in the garden. However, a bin which is not enclosed will also be susceptible to rodents and animals, pets and pests which will destroy your compost.

As well as unwanted rodent and pest visitors, composts are notorious for their bad smells. These can either waft around your entire garden, or pack an almighty punch when you lift the lid. The reason for these smells is that your compost has become anaerobic and is producing bad smelling gases. Therefore, turn the compost, or change the compost method to allow better airflow. Another reason for bad smells is that the compost has too much nitrogen rich materials. This is rectified by adding more brown materials such as dry leaves, straw, sawdust, cardboard or newspaper.

Types of bins include a round cylindrical-type vat, in which you add waste into the top. Another common bin type is a round drum suspended so that you can turn the contents over. Compost bins are usually made from plastic, however a variation is chicken wire set up around stakes to form a cylinder shape. A compost heap is the cheapest alternative, as it is, as the name suggests, a heap. However this will be smellier and slower than a compost bin, and is more difficult to aerate, and is unprotected from rodents. Compost trenches are another method, which is slightly better than a heap, but still will have similar problems with rodents and pests.

A new product on the market called the Aerobin reduces the amount of problems commonly associated with compost bins through its design. It has an aeration core or lung that enables airflow throughout the compost. It is also insulated to keep the heat within the bin, and stores the water created from this heat in a leachate tray at the base. This can be let out via a tap as a liquid fertiliser. An opening at the bottom enables you get out the longest composted material, or humus layer, at the bottom of the bin. The Aerobin is fully enclosed to prevent it from being invaded by rodents and pests. However, this means that worms cant get in to help break down the material. Jodie Anson from Global Environment Management explained some of the benefits of Aerobin.

"The aeration core means you don't have to turn it, and reduces the smell. Aerobin doesn't need to be placed in the sun like other compost bins. It can take kitchen waste such as citrus and onion which worm farms can't," she said.

While an Aerobin may be the fastest and most efficient way to compost, it is also an expensive option at around $300. If you are sick of problems with smell and pests then it may be a wise investment. But remember, composting is a natural decomposition process, which may be sped up through various bins systems. However the principles relating to nitrogen, carbon, air and water do not change regardless of what type of bin you purchase, or trench you dig.

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