Anyone for hot composting?

grownupgreen member Paul Bendall came across a Swedish firm, on his local council’s website, which sold the Green Johanna composter. He shares his experience and asks for yours!

Paul:

The Green Johanna is a compost bin that will also deal with meat, bones, fish and much more. I have just bought a Triobin from www.homerecycling.co.uk and it seemed like a good way to reduce our waste. It arrived in the autumn and I must admit in the past my compost heaps have not been that successful.

So, back to the Johanna, I followed the instructions that came with the bin, it seemed well constructed with air holes in the bottom and top. I filled it up and nothing much happened. I was mixing kitchen waste with shredded paper that we produce from our junk and unwanted mail.

Then just before Christmas I purchased the winter jacket, especially designed for the Johanna, which is basically just some foam to go around the bin. Now it has a new life and is very active the contents look more like compost already and it is steaming away. I decided to get the thermometer so see just how hot it was. It arrived and I fitted it straight away. It immediately registered around 50 degrees C just a few inches under the top.

Everything goes into the compost apart from peelings which goes to the wormery. We put in meat, bones, sauce, paper, grass, cardboard the lot. I use the “stick” that came with the compost bin – a wooden stick with a two hinged metal plate at the bottom. Every Saturday I empty the green bins, paper and cardboard. I drive in the stick, the plates close, and then pull it up and the plates open lifting the compost. I guess this lifts and aerates as well as mixing the layers. It is very easy and I am amazed at the results already. At the end of the day it is still quite cold yet I am still hot composting!

I would like to know if this process needs careful management so it doesn’t get too hot and kill bacteria. I have read that air is very important to keep it aerobic so I have thought about adding a tube with holes in it to act as a chimney. Also does the process produce methane which is obviously a green-house gas?

Well Paul you certainly sound like you are doing something right. You mentioned your wormery and as you know we have a worm expert to hand so we’ve posed your questions to George Pilkington and here is what he had to say.

George Pilkington

Hi Paul

I have seen these composters, although I have no direct experience of them myself. I wasn’t too impressed because I think that it takes too long before you can use the compost. I believe the basic theme for this model is ‘chuck your stuff in it and forget it for many months’.

As it is buried in the ground, little air can get into the unit from underneath to keep it aerobic. I would suspect that the compost produced would be anaerobic and although still a useful by-product it is not as useful as aerobic produced compost. This is because of the potential leachates produced by the anaerobic microbes who also produce methane.

Paul, you could well be actively using the composter to produce aerobic compost, which is a much better use of a compost bin, although the one you are using is rather small.

Here is some more information that I hope you may find of interest….

Compost heaps consist mostly of organic matter, not mineral as in soil. It could aptly be called young soil or even immature soil. A compost heaps would certainly not have all of these ‘hot spots’ but would, given the right conditions, create it’s own ‘hot spots’ of microbial activity due to the much larger volume of material decomposing at one time. Certain compounds that decompose in a compost heap may occur at rates that are unique to composting within heaps. Natural decomposition factors are largely imposed externally by physical factors, such as temperature, moisture content and density. This ‘natural’ process for most purposes is slow and stable. The same physical factors apply to composting, but these are a consequence of internal events and the decomposition process is much more rapid and although a ‘natural’ process it is a manipulated one.

Want to know more about the Composting Process?

YOUR Comments

Has anybody used the EM Kitchen Waste Digester which is a Japanes invention where you can compost all things and it is ready in 2 weeks time. Is this equally as good as using a traditional composter? I am thinking of investing in one – but would like to know if anybody has used them.
T.B

I started to read about composting, first from Paul then from George, but it then became technical, I lost the thread halfway through, maybe I need diagrams!!
A.S

Paul Bendall and George Pilkington - 24/04/06

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