Making Compost - part 1

Your fruit and vegie garden will really benefit if you make your own compost.  This blog post explains how good compost is made. It also provides many tips and hints that will help you to produce nutrient-rich compost that your garden will love.

Why make your own compost?

• Making compost in your own garden from your own food scraps and garden waste is an efficient way of processing these materials ‘at source’. As a society we throw away too much. Your compost heap can help keep your food and garden waste out of council landfill areas.

• Compost made by you is probably going to be of much better quality than commercially produced compost and it won’t cost you a cent.

• Good compost is one of the key factors for a food garden a success, so why would you give away to your council the ingredients to make it.

• It is a great feeling to enrich your garden with your own 'black gold’.

• Rather than adding fertilisers directly to your garden where they might be too harsh and harm beneficial organisms in your soil, your can use a compost heap to transform them into substances that can easily be taken up by plants and that will make your beneficial soil organisms thrive.

Good compost is made by combining ....

• Brown materials – stalks, twigs, dead flower heads, straw, hay. They provide carbon which  enables fungi to help in the breaking down process.

• Green materials – grass clippings, green leaves, weeds, vegetable and fruit waste, coffee grounds. They provide nitrogen that will attract bacteria. 

• Water – a compost heap should always be damp, but not sodden. A dry heap will simply sit there and not compost. A compost heap or compost bin that is too wet will be subjected to anaerobic composting, composting without air. It results in a foul-smelling soup that is not good for your soil.

• Air – the composting method discussed in this blog post is aerobic composting, composting using air. Air will initially be trapped when a compost heap is set up. A compost heap needs to be turned from time to time to aerate it and keep the aerobic composting process going. 

To set up a successful compost heap you need to ....

• Choose a location that is not in full sun (so your heap does not dry out). However, do not put your compost heap in the shade of a tree, because its roots will happily invade the heap and take away a lot of the nutrients. The shady side of a building is usually a good spot. Compost enclosures, from ultra-simple to quite elaborate, are discussed in Making Compost - part 2.

• Start it when the average air temperature is above 10 degrees C, so the composting process has no difficulty starting. In Tasmania this means: winter is not a good time to start a new compost heap.

• Collect as much garden waste as possible. The more garden waste, branches, pruning clippings, vegetable scraps, lawn clippings and weeds you have when setting up a heap, the better the composting process will work. 

• Cut or shred thicker or larger ingredients into smaller bits so they will break down more easily.

• Make sure you have a combination of brown and green materials in your heap. Compost for vegie gardens (where bacteria are more important than fungi) is best made with approximately equal amounts of greens and browns. If your compost is meant for fruit trees (fungi are more important here than bacteria), then have more browns than greens (a 6:4 ratio is good). 

• Make sure that the various ingredients of the heap, especially grass clippings, do not form dense layers. Thoroughly mix all ingredients with a fork, while spraying water, so everything becomes damp, but not sodden.

• Add some blood and bone while mixing. It will help to get the composting process going and will add good ingredients.

• If you have them available, add fertilisers such as seaweed meal, diluted liquid kelp, worm castings, worm juice, seed meal, rock dust, or biochar, to your compost heap when you set it up. They will make the result even more nutritious. Adding some clay slurry can also improve the nutritional value of the compost (see Composting with Clay). Add lime if you want your compost to be more dominated by bacteria.

• Cover the heap with an old carpet to keep heat in, to avoid drying out in hot weather, and to avoid water-logging when there is a lot of rain.

There is 'hot-composting' and 'cold-composting'

Councils that collect green waste shred everything on arrival at their tip, then with large backhoes mix all ingredients, add water while mixing and then make enormous heaps. Organic farms and people with large properties, who have plenty of organic material, will do something similar. Ideally these heaps heat up quickly to around 60-65 degrees Celsius. Large heaps can heat up to much higher temperatures, depending on what the air temperature is and what is in the heap. They are turned over a number of times and the whole composting process is usually completed in about three to four weeks. This is hot- composting. For hot composting the initial heap needs to be one cubic metre at the very least. Most heaps are much bigger. When you open a hot-compost heap it can be so hot inside that you don’t want to touch it.

People with small gardens will seldom have enough organic material at one given time to make a large-heap that will generate high temperatures while composting. That does not mean they can’t make compost. The method used by people who have small amounts of organic materials is cold-composting. This is a misleading term because, when the cold-composting process takes place, the heap is not cold. It will feel warm when you open it up. Cold-compost heaps simply don’t become as hot as hot-compost heaps because the amount of material is too small to achieve very high temperatures. Perhaps they should be called 'backyard compost heaps'.

Comparing hot-composting with cold-composting

Amount of organic material:

For hot-composting you need at the very least one metre x one metre x one metre (1 cubic metre) of green and brown organic materials. Ideally you have a lot more. This means that for many suburban gardeners hot-composting is not an option.

The types of organic materials:

Weed seeds, aggressive grasses and pest-affected organic wastes are far less of a problem when you hot-compost. The high temperature will break down most of them. In most cases hot-composting produces clean weed-free and seed-free compost. When cold-composting, some of the weeds, seeds etc. will survive the composting process and become part of the compost that you spread on your garden. To avoid this, it is best not to include aggressive weeds and seeds and pest-affected material in your cold-compost heap.

The time the composting takes:

Hot-composting is much faster than cold-composting. Depending on the season, the size of the heap and what you are composting, hot-composting may take a 3-4 weeks, whereas cold-composting may take 3-4 months. No comparison.

Is the end product the same?

No, it is not. Many micro-organisms and worms, do not survive hot-composting. The compost you buy in bags in hardware stores or in scoops at garden supply businesses is the result of hot-composting.  It is in many cases completely seed-free, which is great. However, it will be a lot less alive with worms and micro-organisms than compost made by cold-composting. Hot compost heaps often become much hotter than the desired 60-65 degrees Celsius. I have seen a large hot-compost heap burn at a local tip. The result of burning is ash. Ash is alkaline. Some commercially produced composts will have a pH of well over 7. This is not what you want for growing vegetables. Commercially produced composts are great for many garden situations, but some will not be great for vegetables. For growing vegetables, the 'black gold' produced by cold-composting nutritious materials and additives is the way to go.

This is how I do my cold-composting

From materials I bought at the tip shop I built two compost bays. 

When I have completely emptied a compost bay ......

• I make sure I have a fair amount of 'browns and greens' from my garden, 3 or 4 bags of sheep manure, 1/4 - 1/2 litre of blood & bone, and two or more standard-buckets of kitchen scraps.

• I mow the grass in our garden. Grass clippings are full of nitrogen and ideal of starting off the composting process.

• I put my 'browns and greens' in the empty compost bay and chop them up into small bits if needed. I add the sheep manure and kitchen scraps and mix it all thoroughly with a garden-fork, adding water here and there, so everything is nice and wet, but not sodden. While mixing I sprinkle the blood & bone, so it is nicely dispersed over all the material. I finish by putting a strip of old carpet from the tip shop over the top to keep warmth and moisture in and sun out and to make sure excessive rain does not drown the heap.

• In coming weeks I will save up more garden waste, that once again I cut or shred if needed. Initially I simply put it on top of the new small heap, just under the piece of carpet.

• When I have a fair amount of  new material, I once again add the content of the kitchen scrap bin and mix all the new ingredients in with what was already there. This process aerates the heap. I might also once again add blood & bone or complete organic fertiliser (COF – see Complete Organic Fertiliser on this blog) and sprinkle water if the mix is too dry. 

• It may sound funny, but while you are remixing it all, ‘smell your heap’. If the smell is foul, aeration is inadequate. You may have too much moisture (don't add more water, leave the carpet off the heap for a few days, or add more dry material). You may also have excessive nitrogen (add more 'browns', don't add more grass clippings or blood & bone). If the content of your heap looks dry, add more water.

• By now my trusted workers (worms) have miraculously found their way from the adjacent compost bay to the new heap, and are hard at work processing all the yummy ingredients.

• I add more material every 3 - 4 weeks until my righthand heap fills most of this compost bay. Time from starting a new heap to taking away the resulting compost may be 4 to 6 months.

• When the bay is almost full, and the compost in the adjacent bay, that has been sitting there for a number of months, is ready for use in the garden, I empty that bay and repeat the whole process.

There are many variations on this theme. People with chooks may use chicken manure, which is much higher in nitrogen than sheep poo and better at starting the composting process. Just make sure you don't add too much.

Do not add the following things to a cold-compost heap

• Salt, fat and cooking oil. 

• Farm manures are fine, but not if the animals have just been wormed. If you buy manures in most cases you won't know.  Cat, dog or other pet droppings should also not be added.

• Clearly diseased garden waste, eg. rose clippings with black spot or tomato leaves with mildew.

• Any material that you know has been treated with a herbicide or pesticide or weed killer or chemical fertiliser because they may kill the beneficial organisms in your heap.

• Small quantities of printed paper and cardboard are fine. However, newspapers and cardboard often contain ink and glue that can be poisonous, if used in large amounts.

• Large quantities of pine needles, pine bark, brown leaves, sawdust and wood-chips don’t break down well, and are too acid to make compost for vegetable gardens.

How to avoid mice, rats and native wildlife

Some areas of Hobart have a rat problem, much more than other suburbs. To me, making compost is such an integral part of having a food garden that, if I feared that my compost heap would attract rats, mice or native wildlife, I would definitely still have a compost heap, but consider the following measures:

• Make your compost in a compost tumbler (more about compost tumblers in Making Compost - part 2).

• Construct a compost bay or bays that rodents and others can’t get into by not leaving any gaps between timber planks and using fine mesh to cover your bay(s) completely. Give the compost bay a lid covered with mesh and consider having a floor of mesh as well.  There are many ideas for compost bays in Making Compost part 2 .

• Frequently turn your compost heap and make sure it is damp. This will create an uninviting environment.

• Don’t put vegetable scraps directly in the compost heap, but store them in an inaccessible outside bin until they have broken down somewhat. Make sure that, once on the compost heap, these scraps are always well-buried.

• Consider getting a watchful dog that keeps an eye on everything that goes on in your garden. Anything that moves at ground level will be discouraged from coming back.

Composting is a hot subject

While preparing for the writing of this blog post, I compared the advice by a number of experts on the subject, and guess what? They don’t always agree, and I bet that if they met, they would have a heated discussion.  If you would like to comment on this blog post, please send your remarks to foodgardengroup@gmail.com , because there is always more to learn.

Making Compost - part 2 discusses .....

• The ideal spot for a compost heap
• The simplest compost heap structure
• Using mesh and a pallet
• Compost bays
• Plastic compost bins
• Compost tumblers
• Shredders
• A great use of shredder, sieve and tumbler

Related blog posts that are also worth reading:

• Microbes in your Soil
• Compost heap and Worm Farm
• Backyard Biochar
• Composting with Clay

Happy composting!