The logic of compost tumblers goes like this: Lack of aeration makes compost piles stinky and slow. By turning the compost regularly, we add air through the pile and the compost will break down faster and not smell. Sounds good… in theory.
If our approach to composting is to ‘Tip and Run’, a tumbler will not improve our compost much. If we give the tumbler a few turns each day (or, will that be each week?), inside the tumbler all the wet, nutrient-rich scraps will ball up into stinky ‘food balls’, stodgy in winter and dried to hard crusts in summer.
One of the good features of tumblers is the rodent-proof processing they provide, but vinegar flies will likely find their way through the ventilation holes (which are essential for aeration), and compost leachate (brown nutrient-rich liquids) will drain out the holes and joints of the tumbler.
If we progress from ‘Tip and Run’ composting, and start put a more balanced compost blend in our tumbler, adding carbon-rich ingredients like straw, woody garden prunings (chopped up short), autumn leaves etc. to our kitchen offerings, we’ll find the aeration needs of the compost have actually been met by the air pathways in the structure of these materials.
Tumbling this better balanced compost mix won’t really help it much. A balanced, but slightly dry mix will tend to dry out further when tumbled, particularly in summer. A wetter mix can still end up clumping into balls when tumbled. Fungi and worms both hate all that agitation, so will do poorly in regularly tumbled compost, so tumblers really depend on bacteria and oxidation to do the heavy lifting of decomposition.
Most modern tumblers are not very big, and will fill up quickly if we put a balanced compost mix into them. Larger tumblers get very heavy and become quite hard to turn, but, even in smaller tumblers, the weight of the wet compost can be significant, putting a lot of stress on the pivot mechanism and joints. This is probably why tumblers are such a common hard rubbish item.
Probably the best use for a tumbler is as a food scraps pre-treatment processor, providing a rodent-proof, bacterially active environment for a few weeks to make food scraps unpalatable to rodents. This ‘early stage’ compost could then go into a bin or bay for fungi and worm curing for several months. But that would involve getting pretty fresh compost out of the tumbler’s ‘hatch’… another not so great design feature!
I do think tumblers might be over-complicating the compost process. A Gedye-style bin with rodent mesh over the bottom provides the rodent proofing we need for cool composting, and with no moving parts to fail. If we want good compost, we still need a balanced blend of ingredients, which should have all the aeration it needs in its materials, no tumbling required.
Perhaps you have worked out a great way to use tumblers. We always love to hear from you.
– Joel Meadows works with *Yes In My Back Yard, (YIMBY), a community-scale composting initiative in Castlemaine and surrounds. Send questions or comments to hello@yimbycompost.com, or to book in for a compost workshop!
