Compost Tumblers: Are They Worth It?

Good at some things, oversold at others.

A tumbler is a sealed drum on a frame that you spin instead of turning a heap with a fork. They are the most heavily marketed piece of composting equipment there is, and whether one suits you comes down to a handful of things nobody puts on the box.

What a tumbler is genuinely good at

• Keeping vermin out. A sealed drum off the ground is the single best answer to rats, and it is the reason most people end up buying one.
• Small spaces. It works on a balcony, a courtyard or a deck where an open heap is not an option.
• Neatness. Nothing is visible, nothing smells if it is running properly, and no neighbour ever complains about one.
• Effort. Turning a drum takes seconds. Turning a heap takes a fork and half an hour.

What it is bad at, and the honest limits

• Volume. A typical tumbler holds a fraction of what a bay holds. If you have a real garden producing real quantities of prunings and spent crops, a tumbler will not keep up and was never going to.
• It is a batch system, not a bin. This is the part people get wrong. A tumbler works by being filled, closed and finished. Adding fresh scraps every few days means the contents never all finish together, so nothing is ever ready.
• No worms, no soil contact. Off the ground it relies on bacteria alone, so it misses the whole soil food web an open heap recruits.
• It goes wet and slimy easily. Sealed means no drainage, and kitchen scraps are mostly water.
• Not as fast as the marketing claims. Two weeks is a laboratory number. Six to ten is realistic.

How to actually run one

Almost every failed tumbler is failing for the same three reasons, and all of them are fixable.

1. Run two, or run it in batches. Fill one, close it, and start the second. This is the single change that turns a tumbler from disappointing into useful. If you only have one, stop adding once it is two thirds full and let it finish.
2. Far more browns than you think. Aim for roughly two parts dry brown material to one part kitchen scraps by volume. Shredded cardboard, dry leaves, straw, sawdust from untreated timber. A tumbler that is slimy is a tumbler short of browns, every time.
3. Chop everything small. There is no soil life in there to break down a whole cabbage stalk. Anything bigger than a few centimetres will still be recognisable in three months.
4. Spin it every two or three days, not daily. Constant turning stops the heap ever holding heat.
5. Check the moisture. It should feel like a wrung-out cloth. Too wet, add browns. Too dry, add a little water, because a sealed drum in the sun dries out faster than an open heap.

Should you buy one?

Buy a tumbler if you have a small space, a rat problem, or you have tried an open heap and hated turning it. Do not buy one expecting it to replace a compost bay on a productive block, because it will not, and do not buy the smallest one you can find. Capacity is the thing you regret.

The best setup for most gardens with room is both: a tumbler by the back door for kitchen scraps, and a bay down the garden for prunings, spent crops and the bulk of it.

See also: The composting guide for open heaps and bays, and the compost calculator for getting the browns and greens right.