How a compost heap works

Composting is decay managed so it happens in a heap rather than in a landfill or a smelly bucket. Microbes and, later, worms do the work. They need food, air, and water. Exclude any one of those and the heap stalls or turns sour.

Gardeners talk about greens and browns. Greens are soft and nitrogen-rich: vegetable peelings, grass, coffee grounds. Browns are drier and carbon-rich: torn card, dead leaves, woody prunings. A heap of only grass slumps into a wet mat. A heap of only twigs sits there. A mix of both gives the microbes a balanced meal.

Greens and browns

Air comes from structure. Twigs and torn card stop the heap compacting. Turning it, every so often, brings the outside to the middle. A sealed bin with no airflow goes anaerobic, which smells of rotten eggs and works slowly.

Moisture should be that of a wrung sponge. A dry heap pauses. A sodden heap drowns. In a wet climate a lid helps. In a dry spell a watering can is the tool. Kitchen scraps are wet, so balance them with card.

Heat, air, and time

A well built heap heats in the middle as the microbes respire. The heat is a sign of activity, and it hurries the decay. It is not a steriliser you should rely on for diseased plants or for cooked food that attracts rats. Keep meat, fish, and cooked scraps out of an open garden heap.

Finished compost is dark, even, and smells like soil. You should not recognise the peelings. Dug in, or spread on a bed, it returns organic matter to the ground. The heap is a slow factory, and the product is the soil’s lunch.

Greens and browns

A compost heap turns kitchen scraps and garden waste into a dark, crumbly soil-maker. Air, moisture, and a mix of materials are what the decay needs. Composting is decay managed so it happens in a heap rather than in a landfill or a smelly bucket. Microbes and, later, worms do the work.

Put those two statements side by side. The first sets the condition. The second says what happens once that condition is met. How a compost heap works needs both. Drop the first and the second has nothing to explain. Drop the second and the first is only the scene.

Heat, air, and time

Microbes and, later, worms do the work. They need food, air, and water.

The order is the explanation. What the first sentence names has to be there before the result in the second sentence can show up. The piece does not ask you to accept the result first and hunt for a cause afterwards.

A check you can make

They need food, air, and water. Exclude any one of those and the heap stalls or turns sour.

A fair check is sequential. Confirm the first statement. Then see whether the second is the result of it, rather than a separate fact parked in the same piece. If the result shows up without the condition, this account does not cover what you are looking at.

The limit of the claim

Exclude any one of those and the heap stalls or turns sour. Gardeners talk about greens and browns.

The two statements do different jobs. One says what is there, what it is made of, or what acts on it. The other says the change that follows. The title names the change. It is not an inventory of parts.

The same steps, in order

Gardeners talk about greens and browns. Greens are soft and nitrogen-rich: vegetable peelings, grass, coffee grounds.

Nothing in the second statement cancels the first. It carries the first forward or marks the limit of it. Remember only the result, and the cause goes missing. Remember only the cause, and you will not know what the piece says happens next.

Why the order matters

Greens are soft and nitrogen-rich: vegetable peelings, grass, coffee grounds. Browns are drier and carbon-rich: torn card, dead leaves, woody prunings.

Read them as one path. Start at the first full stop and do not skip to the outcome. The words between the two statements are the mechanism. The title is the name of that path, not a second claim.

Condition, then outcome

Browns are drier and carbon-rich: torn card, dead leaves, woody prunings. A heap of only grass slumps into a wet mat.

The first statement can be true and still not finish the job. The second statement is the job finishing. Hold both, and the paragraph above stops being a list. It becomes the reason the title is worded as it is.

What the title is naming

A heap of only grass slumps into a wet mat. A heap of only twigs sits there.

If you wanted a shorter version, it would be those two sentences and nothing else. Everything added around them is there so the dependence is obvious: the second does not happen unless the first has happened.

What has to come first

A heap of only twigs sits there. A mix of both gives the microbes a balanced meal.

Put those two statements side by side. The first sets the condition. The second says what happens once that condition is met. How a compost heap works needs both. Drop the first and the second has nothing to explain. Drop the second and the first is only the scene.

The result that follows

A mix of both gives the microbes a balanced meal. Air comes from structure.

The order is the explanation. What the first sentence names has to be there before the result in the second sentence can show up. The piece does not ask you to accept the result first and hunt for a cause afterwards.

A check you can make

Air comes from structure. Twigs and torn card stop the heap compacting.

A fair check is sequential. Confirm the first statement. Then see whether the second is the result of it, rather than a separate fact parked in the same piece. If the result shows up without the condition, this account does not cover what you are looking at.

The limit of the claim

Twigs and torn card stop the heap compacting. Turning it, every so often, brings the outside to the middle.

The two statements do different jobs. One says what is there, what it is made of, or what acts on it. The other says the change that follows. The title names the change. It is not an inventory of parts.

The same steps, in order

Turning it, every so often, brings the outside to the middle. A sealed bin with no airflow goes anaerobic, which smells of rotten eggs and works slowly.

Nothing in the second statement cancels the first. It carries the first forward or marks the limit of it. Remember only the result, and the cause goes missing. Remember only the cause, and you will not know what the piece says happens next.

Why the order matters

A sealed bin with no airflow goes anaerobic, which smells of rotten eggs and works slowly. Moisture should be that of a wrung sponge.

Read them as one path. Start at the first full stop and do not skip to the outcome. The words between the two statements are the mechanism. The title is the name of that path, not a second claim.

Condition, then outcome

Moisture should be that of a wrung sponge. A dry heap pauses.

The first statement can be true and still not finish the job. The second statement is the job finishing. Hold both, and the paragraph above stops being a list. It becomes the reason the title is worded as it is.

What the title is naming

A dry heap pauses. A sodden heap drowns.

If you wanted a shorter version, it would be those two sentences and nothing else. Everything added around them is there so the dependence is obvious: the second does not happen unless the first has happened.