Compost is basically the equivalent of the good stuff in soil (humus) that sustains plant life. It helps the soil retain moisture, assists with the formation of good soil structure and provides nutrients.

So much of what we send to landfill consists of materials that could be used in our garden. Around 200 pounds of vegetable waste is thrown out by each family, each year. Multiple that by millions of families and that's a lot of garbage that has to be transported.

By setting up your own compost pile you'll not only be helping your garden, you'll be helping the planet in other ways.

Composting seems to be such a simple concept - throw stuff in a pile, it breaks down thanks to bacteria and other critters - but nature works some amazing and complex magic for this to happen. Nature never ceases to leave me in awe; even when it comes how it deals with its own garbage.

When we hear the term "bacteria", we often associate it with nasty stuff, but bacteria are essential to our health and the well-being of our planet. For example, without certain bacteria in our digestive system, we wouldn't be able to process food properly and would become quite ill.

There are three different groups of bacteria that are involved in the composting process and each successive group relies upon the prior in order to do their work most effectively.

Psychrophilic bacteria

These are the "starter bacteria" that go to work on cold compost. They are most active in temperatures of 55°F, but will also work down to an incredible 0°F (-17°C). As these bacteria chomp on organic materials they also generate a small amount of heat, creating an environment suitable for the next group.

Mesophilic bacteria

These work in temperatures from 70° - 90°F (approx. 15°–40°C), decomposing both vegetable and animal matter. Their exertions produce enough heat to for the next type of bacteria.

Thermophilic bacteria

These are the powerhouses of the bacteria world; working fast, in a temperature range of 104°F to 170°F, but some will also still thrive past the boiling point of water! These are the guys that can cause a compost pile to spontaneously combust if the pile is too high or too dry.

These three groups join forces to turn our trash into rich humus capable of sustaining plant life; but they are also assisted by other organisms such as fungi, various insects and worms (see my article on vermicomposting).

Quick composting tips

By providing the best conditions possible, the composting process can be made to happen much faster than it does in normal natural conditions. Whereas everything just chucked in a pile may take a year or two to break down and sometimes with undesirable results; intensive composting can be completed in just a couple of months.

Here are some simple things you can do for more effective composting.

- Experts say it's important to get the right mix of carbon and nitrogen materials in a compost heap. The carbon based stuff is mainly dry; things like newspaper, straw and dry cuttings. The items rich in nitrogen will mostly be wet - vegetable scraps and lawn clippings. Ideal conditions are said to be 1 part wet/green to 25 parts dry/brown. If you won't have this sort of balance, don't be overly concerned - I have a compost pile that is almost exclusively paper and cardboard and in the case of many households, much of their compost pile will be vegetable scraps. Just bear in mind an overly dry compost heap will take ages to break down (been there) and one too "green" and wet will start to smell (been there too).
 
- Care needs to be taken when adding lawn clippings. These are usually very moist and rich in nitrogen. As they are so wet, they'll clump together, dispelling the oxygen needed by the aerobic bacteria and the pile will get quite smelly - a strong ammonia type whiff due to anaerobic decomposition. It's best to mix clippings in thoroughly with the pile, or spread the lawn clippings out for a few days to dry a little and then add them.

- Select a well drained area to establish your pile; preferably over soil so that worms can access it. The compost pile should be in a sunny position in colder climates or a shady area in warm climates

- A three sided pen will help to keep your pile tidy. This can be made from star droppers and strong mesh or pallets nailed together

- To speed up composting, break down materials into smaller pieces or shred

-It's really important to turn the pile regularly if you're not going to be bothered with layering wet and dry waste and you'll just be chucking stuff into your compost pile as it comes to hand - particularly if much of it will be "green"; such as vegetable waste. Turning compost introduces more oxygen into the pile so the bacteria can do their work and brings more material into contact with the bacteria. It can help speed up the composting process and prevent nasty odors. Turning a pile within a small barrel can be awkward, so I use a purpose-made compost turner, which consists of a spiral of steel with a T-bar at the top for turning. The spiral digs down into the compost and when you pull it up, a plug of materials comes with it. It's a very inexpensive, simple yet effective tool that you can purchase at many hardware and garden stores.

- The pile should always be quite warm - if you dig a small hole into the pile and put your hand near it, you should feel it being warmer than the air temperature. If it's cold, you need to add more green stuff.

- The pile should always be moist, but not dripping. If it's dry, spray water on the pile and then work it through.

If you're thinking of getting into composting in a big way; there's all sorts of tools available such as bins set in frames with a handle for turning. A multiple bin/pile system is also useful so you can stop with one pile at a certain point and let that totally decompose while adding fresh stuff to a new pile.

Things you can add to compost piles

Newspaper, cardboard, eggshells, vegetable scraps, law clippings, cuttings, hair, manure from herbivores, leaves, sawdust, coffee grounds and filters, tea leaves - basically any plant material that that's not too thick.

Things to avoid

Dog and cat droppings, fish, meat and dairy products, weeds, grease and oil. The reason for avoiding most of these is that there is a disease risk and rodents and other animals may be attracted. I have composted dog droppings before, but basically in a bin of their own with lawn clippings. It doesn't smell all that good during the early stages :). If you do compost pet droppings, don't apply the resulting compost to a veggie garden; just to be safe.

This has just been a primer on the topic of composting and I'm certainly no expert. For some people, composting is an absolute passion and they go about it in a very scientific way, so there's a stack of information around the web about various approaches and equipment.

By the way, if your home doesn't have a yard, you can compost small amounts of materials indoors without an mess or odor using a Bokashi composting system.