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What goes in a compost bin?

What goes in a compost bin?

Vegetable trimmings, stale bread, food leftovers, apple cores, orange peel, wetted newspaper,banana skins, coffee grindings, to name but a few.

Egg shells are good, but wash them out first to avoid smells.

NO fish, meat or bones.

The exception for fish or meat, is where you have a large established compost heap, and it is possible to bury the meat or fish deeply into the pile.

For a normal compost bin, the food waste and vegetable trimmings should be chopped as much as is sensible.

Think variety!

Add a good variety of materials, and try to soak up the moisture by adding torn up newspaper to any really wet vegetable or food waste.

Avoid adding too much wet waste at once, and just mix the new waste into the surface of the existing material if possible.

Too much wet grass clippings can become slimy, purely because of too much moisture and the nutrients in grass ferment very quickly to make a bad smell.

For grass clippings, add torn up newspaper or dry sawdust, if available, even if you have a large existing compost heap.

If you can get a nice level of moisture (no more than 75% by volume) the compost will heat up better because some oxygen can percolate through a drier material more effectively.

Creating great dark compost

Both hot and cold composting can be effective in producing a dark black compost that is great for the garden soils.

Any organic matter can be composted, in theory, but the level of dryness or wetness is a main consideration.

There are a few materials, like glossy magazines, that will not break down and compost easily.

Egg shells really should be crushed after washing them, just to distribute them around a bit. The calcium in egg shells is good for the general mix, because it reduces local acidity where some smells could arise from.

A good supply of dry wood sawdust is very helpful, so you can add a bit with every fresh amount of composting material.

The C:N ratio

Quite often, there is an over-supply of ‘free’ nitrogen in things like grass clippings and vegetable waste.

This should be balanced by adding things that are high in ‘carbon’.

Things high in ‘carbon’ are usually the more brown and dry materials, like dead autumn time the brown, dead leaves are great to load in with grass clippings.

There is a recognised ratio of carbon-rich materials to nitrogen-rich materials.

It is around 25 carbon to 1 nitrogen.

This means quite a lot of dry brown materials, like sawdust, need to be added to the grass clippings, which are, usually, wet or moist.what goes in a compost bin

When you get this mixture correct, the hot composting process will start very quickly, and you will know because the compost will start to heat up.

Checking your compost

You can tell a lot about the state of your new compost by what type of smell is coming out of your bin, or heap.

If the smell is bitter and is more of a stench than a more pleasant sweet fermentation smell, then you know that more browns must be added by mixing in, if you can.

Browns and greens are the easy way to think of the wastes that you add to whatever bin or heap that you use.

Your shrinking compost!

It is surprising how much your various waste materials will shrink during the composting process.

This is because if, say, the vegetable waste is only 15% Dry Matter (DM), then it follows that the remaing 85% is just water.

As the composting gets going, (whether hot or cold composting) most of the water is lost by evaporation or chemical breakdown processes.

A number of processes occur including both physical effects of small invertebrates, eg beetles and nematodes, and biochemical effects which release gases such as carbon dioxide and methane.

Some sulphurous gases can be released if the mixture is not balanced well.

Turn your heap or bin, if possible.

Compost usually benefits from some form of aeration, eg the Rolypig turns the material to allow air to get in properly.

Turning or disturbing in some way, will accelerate heating and will speed up decomposition even if the heap is just a cold heap.

Often, a nice open texture compost will allow air through without much turning, but the general rule is turn every 2-3 weeks if you can, and do this with the batch amount.

Start another batch in another bin, or as a new heap, so that new material does not come out with older compost that is nearly ready to use.

How do I know when it is ready?

Normally, compost is ready when you see no more changes in colour or consistency.

Heating will have finished, and the smell will be a slightly sweet, fermenting sort of smell.

It pays to cover an outside open compost heap as it comes to this point of a stable (hopefully nice dark) colour.

This prevents rain from washing away nutrients, and also makes the compost easier to handle, as it is moist rather than wet.

The role of worms in compost

As soon as your compost is cooling down and becoming darker in colour, this is when the local redworm population will find and colonise your compost, whether in a bin or an open heap.

These little red worms are completely harmless, and, are a welcome sight, because they are telling you that your compost is highly suitable to improve your soil.

You will, often, find redworms in only partially composted material, as long as it is not too hot.

Redworms are a real benefit to your composting operation, and if you keep some old compost around, these worms will live in there for some time, until they have eaten through it several times and then move on to the next fresher compost bin or heap!

You really know you are doing composting right, if redworms are all over the outside of your bin.

Knowing what goes in a compost bin, now, you are ready to start!

Handling precautions

As with any waste materials, it is wise to wear rubber gloves, in case any harmful microbes are present in the fresh waste.

Composting will destroy most pathogens, but always make sure you wash your hands before eating after handling any compost or food-waste.