There are an awful lot of adverts for compost tumblers. Some you roll along the ground. Others rotate on a base. Some rotate around a central axle. Still more are cranked with a handle. All suggest that they give you compost more easily and in less time than a bin which sounds very attractive. So, is a tumbler something that you should consider?
In 2011 Which? Gardening magazine in the UK compared turning five well-filled tumblers three times a week with turning a traditional compost heap of the same volume once a week (usually done with a garden fork or spade). Surprisingly they found that, while the heap took around ten weeks, tumblers actually took a month longer to create usable compost.
A decent tumbler makes turning easier, but if you want compost quickly and are happy to do the work, it appears that you might as well stick with a standard compost heap or bin, as long as it's easy to access the compost to turn it. It's considerably cheaper and gives you more exercise.
What you get out of a compost tumbler
Of course, lots of us don't turn compost weekly and wait considerably longer than 14 weeks for it, so cutting the time it takes to make compost may appeal.
Before you rush out and get one, do consider the following, though:
- A tumbler must be easy to turn, or you won't bother.
- A larger tumbler will produce compost more efficiently than a smaller one
- To gain compost in three months, the tumbler has to be well filled in one go. Add to this the time taken to fill it, and consider where you'll compost subsequent material while the tumbler's doing its stuff. Adding more bulk part way through the cycle means that you have to wait longer, so that the later material can break down too. (Some designs, such as the Mantis ComposT-Twin, (available here in the UK) have a second chamber to solve this problem.)
- Compost tumblers tend to be summer workers. Unless they're very well insulated, cold weather prevents them from heating up fully.
There's also undoubtedly a difference between the composts from a heap and a tumbler. It's inevitable because the tumbler doesn't contain worms. Nor can you add worms, because when the temperature rises they can't escape and will die. So, all the good work that worms do in churning material through their guts and adding nutrients is lacking.
What you do get is material worked on by bacteria and fungi. It has reached a high temperature, several times hopefully, which should kill off weed seeds and disease spores and will have a looser, rougher character which can be dug into beds or used as mulch. My experience is that it won't be that 'rich uniform crumble' that comes from a well-rotted heap.
In fact, at this point some people put it to one side to continue to compost, which then allows worms to move in.
Advantages of compost tumblers
There are reasons, though, other than taking the work out of turning, why a tumbler might be useful.
- If you have a rat problem. It's not the only way to combat vermin, but the right choice of tumbler provides an instant solution: something metal, with the compost compartment held well off the ground without needing large air gaps because the tumbling achieves aeration. Tumblers like these also allow you to compost food waste that is normally taboo—small amounts of meat, fish and fat—as the high temperatures will break them down quickly and vermin are excluded.
- If you have back problems which prevent your turning the heap. Choose your equipment carefully. A tumbler that you push along the ground yourself is likely to strain the healthiest back. Those which pivot around a central axle carry most of the compost in the bottom half and can be difficult to swing over. The best for a back problem is likely to be one of the more expensive types which is turned via a handle and geared cogs. These take a great deal of effort out of turning. Check whether you can manoeuvre a wheelbarrow underneath for easy unloading.
- If you have very large quantities of grass clippings and soft sappy material to compost. Too much of this in a normal compost heap causes anaerobic decomposition, leading to unpleasant smells and sludge. A tumbler, because it introduces air so readily, reduces this problem considerably, although dry material is still necessary. Grass clippings halved their volume in about a week when I turned the tumbler daily. They can then be mixed in, if wished, to a normal heap. A tumbler should always have drainage holes to permit liquid to escape, and this, if collected, provides a nitrogen-rich solution for liquid or foliar feeding.
- If you have very limited space to compost. It may be worth considering if you have to site it on concrete (fluid will drip into the container you place under the tumbler, rather than oozing out at the bottom).
- If you enjoy tumbling. I know it sounds daft, but it's actually fun. I trialled a super tumbler — Henchman's Compact Compostumbler (available here in USA) — and can honestly say I loved its high quality construction and ease of turning. In fact, tumbling might get your otherwise reluctant children involved. A three-year-old relative was fascinated by mine and looked forward to more composting at every opportunity.
- If you want an ultra-fast output. Adverts suggest that you can make usable compost in as little as three weeks and yes, I've done it. It's not a piece of cake, and you should ensure that your tumbler comes with instructions specifically for this. Be prepared. The balance between carbon and nitrogen is critical, so ingredients need to be measured. Moisture levels need to be monitored, as does the temperature. The end result is quite rough, but would be useful as a mulch.
By Helen Gazeley