Small compost bin with ingredients and worms.

Can you micro-compost in small bins? We did an experiment – here’s what happened…

One of the essential things compost experts recommend for speedy compost is volume.

And this is true – to an extent.

I can attest to this. I used to struggle to get my smaller compost heaps going. But when I built a large compost heap using pallets, I would find, when I turned my heap, that the compost was steaming hot inside.

But there are many variables to compost. And as many people don’t have access to a garden, I wanted to find out if there was a way to successfully micro-compost in a small, closed bin.

Particle Size

Volume is one variable that is important in the composting process, but the size of the individual elements of the compost is also important. That’s because smaller particles increase the total surface area that microorganisms can feed on.

Indeed, when I am feeling particularly enthusiastic, I will chop up the individual elements of my compost pile with a lawnmower, but most of the time I can’t be bothered.

Another element is oxygen. For efficient aerobic composting, the bacteria in compost needs about at least 5% oygen. Some compost methods advise turning your compost on a twice daily basis, but frankly I’ve got better things with my life than turn 50 cubic feet of compost every two days. In fact, my large compost pile only gets turned twice before use, while No Dig expert Charles Dowding only turns his compost heaps once before use.

But what would happen if you got every element apart from the volume? I decided to find out. And even though conditions could have been more ideal, things are looking good so far.

The Experiment

To conduct the experiment, I took the contents of two food waste bins that I keep at work. These are mostly filled with coffee grounds, blue paper towels and bits of fruit (a handy combination of high carbon and high nitrogen materials). I tipped out the contents on my lawn and chopped them up with a lawnmower, in the process adding a little grass and a few leaves.

That vastly reduced the volume and I added the contents to one of my Bokashi bin. I chose a Bokashi bin as as it allows me to drain off the compost ‘tea’. I also added a handful of compost from an existing compost heap in order to introduce helpful bacteria.

To speed things up, I then added some home made compost accelerator, made with alcohol, sugar, hot water and urine.

By now it was autumn, and the days were cooling rapidly. So I placed the Bokashi bin in a greenhouse in order to take advantage of any remaining sun.

I left for a couple of days, and then stirred daily until it got too dark in the evenings to get to the greenhouse. That sounds like a chore, but it only took a minute or so and was a job I could do while watering the green house. After eight weeks, I am now only stirring at the weekend. I also added some tiger worms to help speed the process up.

How did it go?

To start with, I am surprised that the compost did get warm – in fact, I even found the poor worms climbing up the walls of the bin trying to get out. However, I suspect this may have been at least partly down to some warmer autumn days and the fact the compost was in the greenhouse.

Smell’s going to be important for people composting indoor. I did get a slightly acidic smell of citrus, due to the presence of orange peel, but this was only when I opened the bin.

The compost also decreased rapidly in size, which suggest that it could be a good solution for people who are short of space. If necessary, you could combine the contents of compost bins to reduce the space being used.

In the early days I was collecting plenty of compost tea, which I put straight into the watering can, watered down and added to the plans. This suggest a Bokashi bin, or any closed bin with a tap for draining off liquid, is a good solution.

The food seems to be well on its way to composting, although the paper towels are taking a bit longer. At the eight week stage, especially given the days are working their ways towards zero degrees, I’m both pleased and surprised at the progress.

Have a look at today’s picture, and see what you think!

Not bad for eight weeks in a small container in winter! This container was nearly full originally, but has shrunk to a third of its original size.

How could it have been improved?

I never really expected this experiment to work, so I didn’t put too much effort into it. If I repeat the experiment, I’ll take more care to get the green/brown ratio right.

In an ideal world, the weather would be warmer, but there’s not too much you can do about it!

As mentioned, I used a lawnmower to chop up the compost material. It would be interesting to see if the compost process speeded up if the material was chopped up with a food processor to get an even smaller amount.

One thing that seems to have slowed things down is the blue toilet roll. This gathered together in clumps, and is decomposing slower than the organic material. Shredded paper might work better.

For future experiments, it would be interesting to compare how it works with and without compost accelerator. It might also be interesting to see how compost fares without worms, although given these wriggly helpers can remove pathogens such as E-Coli (source: Science Daily), I might leave out that experiment.

I’m keen to try more experiments – such as truly micro-composting in a jar!

Image at top of post by Allan Handerson

Leave a Comment

Your email address will not be published. Required fields are marked *