Last night I was talking to Mum on Skype about composting. She was frustrated that none of her food scraps were breaking down in the bin she was using. I started to explain that there is more to composting than just throwing all your scraps in a pile and waiting for them to magically turn to compost. I told her I’d send a link to my post on composting and then I realised I never actually wrote that post! So here it is. How to compost….for my Mum.
Composting involves mixing yard and household organic waste in a pile or bin and providing conditions that encourage decomposition. The decomposition process is fueled by millions of microscopic organisms (bacteria, fungi) that take up residence inside your compost pile, continuously devouring and recycling it to produce a rich organic fertiliser. Once you know a few simple principles it’s pretty easy. Nature does her job beautifully.
The Compost Bin (The Oven)
First things first. You need a proper compost bin. Most people say you need a pile no smaller than 3′ x 3′ x 3′ (1 cubic metre), but I’ve found a large, well aerated rubbish bin does the trick. In a previous post I explained how Brendan and I made our own Compost Bins for free.
Decide on the location of your compost bin based on function and aesthetics. Your neighbours probably don’t want to see it, but you want to keep it away from buildings as the decomposition may cause wood to rot. From a functional standpoint, you’ll need a place with good air circulation. Partial shade is a good idea so the compost doesn’t get overheated. Also make sure the spot of land where you place your heap gets good drainage.
We decided to place ours in the corner of our small courtyard. It has easy access to the garden and a water source and is easy to get to from the kitchen, but it is out of the way and utilises a space that wouldn’t have been useful for much else. This photo was taken last summer when we had about 4 hours of full sun per day on that side of the garden. In winter it’s in full shade.
How to build Compost (The Recipe)
I like to think of compost making as a recipe of sorts. There is some science to it, but it’s also an artform. Just remember that you need each of these ‘ingredients’ for your compost to work properly and then you can adjust the recipe to suit your conditions.
The most obvious ingredient for compost is organic waste. This can come from your garden, your kitchen and from a variety of other sources around the home. In addition to our own organic matter, I collect food waste and coffee grounds from work so I can build my compost pile very quickly. Ingredients that can make good compost include:
Browns = High Carbon
- Ashes, wood
- Cardboard, shredded
- Dried Leaves
- Newspaper, shredded
- Peanut shells
- Peat moss
- Dried Pine needles
- Stems and twigs, shredded
Green = High Nitrogen
- Coffee grounds
- Tea bags
- Food waste
- Garden waste
- Green Grass clippings
- Hops, used
- Manures (No dog or cat waste)
- Vegetable scraps
- Weeds (I don’t compost weeds that have gone to seed)
I include roughly a 50:50 mixture of brown ingredients and greens, I tend to layer them and always finish on a brown layer as it stops pests getting into the pile.
To speed up the process of composting, chop or shred larger items so they break down more easily; turn the pile regularly; add big meals to the pile rather than small, regular ‘snacks’; full sun will heat up the pile and speed up the process, but be careful it doesn’t get too hot and catch on fire.
The microbes in the compost pile require water for survival. Too much water means your organic waste won’t decompose and you’ll get a slimy and smelly pile but too little water and you’ll kill the bacteria. The more green material you put in, the less water you’ll need to add. In general your compost should be moist, but not sopping wet – think the consistency of a wet sponge that has been rung out.
Oxygen is also required by many of the microorganisms responsible for successful composting. Give them adequate ventilation and they will take care of the rest. You can make sure that the bacteria in your compost gets sufficient air by turning the pile often using a pitch fork or spade. We can usually leave ours for a few months without turning and it still breaks down nicely, but if the pile gets too wet we spend more time airing it out.
As they eat, the organisms responsible for composting generate large amounts of heat, which raise the temperature of the pile and speeds up decomposition. A compost pile that is working well will produce temperatures of 60-70 degrees C (140-160 degrees F). At these temperatures almost all weed seeds and plant diseases are killed. A “very hot” compost pile will generate temperatures of up to 80 degrees C (170 degrees F) for up to a week or more. You can use a compost thermometer to measure the exact temperature, but we don’t get that technical.
How do you know when it’s cooked?
As organic material in a compost pile heats up it breaks down and takes up less space. A compost pile can shrink up to 70% as it “cooks.”
Compost is finished when it’s a dark, rich color, crumbles easily, and you can’t pick out any of the original ingredients. It should have a sweet, earthy smell. If it’s too stringy or lumpy, it may need more time. We usually sift ours through nursery flats and put any big pieces back in another pile, leaving us with lovely, dark compost. It can take anywhere from three to 12 months to produce compost depending on temperatures, what organic matter you’ve used, how fine the waste material was chopped, how often you’ve turned it etc.
How to enjoy it
We add compost to our soil twice per year, before planting begins each season. We simply spread the compost in a thick layer on top of existing soil, cover with straw and then water it down. Within days earthworms have worked the compost into the soil and the improvement in soil quality can be seen almost immediately.
Here’s what ours looks like before we ‘sift’ it and put it in the garden.