Collapsing composter

If you’ve been following my blog for a while then you’ll have read about my experiments with using large cardboard boxes as temporary compost heaps. I wrote up my experiences for the Master Composters last year, and they appeared as part of a larger piece in the Summer 2010 issue of Organic Way, the quarterly magazine sent to Garden Organic members.

This is the article as I sent it in (it may have been edited for publication in Organic Way, I haven’t checked) – I thought you might like to see it.

Cardboard Composters

At the end of 2008 I bought a new chair for my office, which came in an enormous cardboard box. Disposing of cardboard can be an issue in many households – some places have recycling facilities and others don’t, and although cardboard makes a great addition to the compost heap to balance out kitchen and garden waste, most families amass far too much packaging for a small bin to deal with.

I decided to see whether I could compost a pile of cardboard on its own (much like having a long term heap to rot down woody material), and also whether a large cardboard box would make a good temporary compost bin.

I opened up the flaps of the box and used them as a base to help keep it stable, which also meant that the contents would be in contact with the ground so that worms and other composting organisms could make their way in. Initially I used the base of the box as a lid – but although the box itself stood up very well to bad weather over the winter, the flat lid got soggy very quickly and I added it to the contents to compost down.

Initially as I added waste cardboard I also added a liquid compost activator to add some nitrogen; later on I let the cardboard composter take care of itself. I rapidly filled one giant box and started another – a shortage of cardboard was never going to be an issue!

By April the cardboard was starting to rot down, although it was hard for rain to penetrate beyond the top layers and so the cardboard composter was quite dry. As space opened up in my regular compost bins I started transferring the half-rotted cardboard to those, mixed with garden and kitchen waste, and it quickly rotted down under those conditions.

Eventually I dismantled the cardboard composters because they were taking up too much space (I don’t have a large garden and I already have three compost bins and two wormeries!), but the outer cardboard box remained remarkably intact. I had been sharing my experiences with the readers of my blog and listeners to my Alternative Kitchen Garden podcast and some of them tried making cardboard composters themselves.

Between us we came to the following conclusions:

  • It is possible to compost cardboard on its own, although it’s much easier if the cardboard is wet when added to the heap – if you have a rain water barrel then try soaking large pieces in there for a few minutes.
  • A large cardboard box makes a surprisingly good temporary compost bin, and would be ideal for an allotment or a large garden where it can be hidden away.
  • If the cardboard composter is left for many months then the bottom layers can become quite compacted (but that’s true for any compost heap).
  • Shiny food packaging takes much longer to break down than corrugated cardboard, and some packaging has a thin layer of plastic that has to be removed from the finished compost.
  • A cardboard composter makes a great repository for carbon-rich material that can be used to balance out an excess of grass clippings in the summer to avoid a slimy mess.

So if you’re keen to reduce your waste or to turn as much of it as possible into a resource for your garden, have a go at composting more cardboard.

About me

I attended the first ever Oxfordshire Master Composter training course in April 2008, because I am a keen organic gardener and I wanted to share my love of compost with the world! In my first year as an MC I went out and about and encouraged people in my local area to get stuck into composting; since then I have been promoting composting through my blog and podcast and in my book – The Alternative Kitchen Garden: An A to Z, which has a special entry under M about Master Composters.