The Two Bin Upgrade
A single compost heap is never finished, because the top of it is always new. Two bin composting fixes that with no technique and no expense: one bin fills while the other finishes. It is the single best change most people can make, and almost nobody suggests it to beginners.
The problem nobody names
Picture the standard setup. One bin, fed continuously. You add scraps in January, in June, in November. By the following spring the bottom of that heap is genuinely finished compost, and it is sitting under eight months of half-rotted material you added on top of it.
To get at it you have to excavate the whole bin, which is heavy, unpleasant, and means the material you just dug out and dumped beside the bin now has to go back in. Most people look at that job, decide it can wait, and add another caddy of scraps to the top. The pile is permanently in progress and permanently unusable.
This is not a technique failure. It is a design failure, and no amount of turning, activator or patience fixes it.
What two bins actually does
Bin A is the active one. Everything goes in it: scraps, prunings, browns from the sack.
When it is full, you stop. Bin A becomes the finishing bin and you start filling bin B instead. Nothing new goes into A, so its contents all age together and reach the same state at the same time. In six to twelve months A is uniformly finished, you empty it in one satisfying afternoon, and it becomes the new active bin.
That is the entire method. You have converted a continuous pile, which is never done, into batches, which are.
The cheapest possible version
A second bin does not have to be a bin. Four pallets wired at the corners is a compost bay, and pallets are frequently free. A ring of wire fencing held in a circle works. A second plastic bin from a municipal scheme costs little.
You do not need matching containers, a concrete base or a lid. You need a second place to put material so the first place can be left alone.
If space is genuinely tight, the same logic works vertically in time rather than horizontally in space: fill a single bin, then simply stop feeding it and use a bucket or a bag for the interim while it finishes. Less convenient, same principle.
Where the third bin comes in
The classic allotment setup is three bays: one filling, one working, one finished and being used. It is genuinely better if you have the room, because it lets you keep drawing compost while the middle bay matures.
For most domestic gardens two is the point of diminishing returns. Go to three when you find yourself wanting compost while your finishing bin is still not ready, which usually means your garden has grown rather than your method has failed.
When to make the switch
Autumn is the natural moment. You are about to receive a large volume of leaves, so you will fill the new bin quickly, and the old one gets all winter to sit and finish while nothing much is happening anyway. Come spring you have a bay of usable compost exactly when the beds want it.
The other natural moment is now, whenever now happens to be, because the improvement does not depend on the season and the cost is a few pallets.
What it does not fix
Being honest about the limits: two bins does not make compost faster, does not fix a pile that is too wet or too dry, and does not compensate for a heap made entirely of grass clippings. It solves one specific problem, which is access to finished material, and it solves that completely.
If your heap is stalled rather than merely inaccessible, that is a different diagnosis. Start at compost problems.
Related reading on two bin composting
Timescales for each approach are in how long compost takes, and the batch versus continuous distinction underpins hot composting and cold composting. If you are choosing containers, see how to choose a compost bin, and for what to do with the output, using your compost.
The EPA’s home composting page covers the basic setup if you want a second source.