My composting experiment!

Day 1: Sunday 20th May 2012!

So, the compost bin arrived today! The Tumbleweed Gedye Compost bin to be precise!!

The instructions were reassuringly simple. Begin by filling the bin with 10-15cm of dried leaves and twigs. This provides a layer of trapped air at the bottom of the compost bin - vital to get things started.

On top of the dried leaves came some cardboard which we soaked thoroughly.

The instructions then recommended adding a further 10-15cm of kitchen food waste to provide nitrogen. However our worm farm got all of our kitchen scraps last week so we had to skip this part!




Once the initial set up was complete, we set to work mowing and strimming the lawn along with a fair amount of weeding! The result was a pretty full bin - no wonder that they recommend a 2 bin strategy!!










Finally we added the Tumbleweed hessian blanket and gave it a good watering before re placing the lid tightly. With the blanket helping to push the contents down it should, in theory, promote an increase in temperature within the bin and this will speed up the decomposition of our garden waste leading to our very own home made compost.

The compost will need to be aerated on a weekly basis so more pictures will follow next week when we open the bin for the first time.





Whilst I'm killing time waiting for next weekend so I can aerate the compost bin for the first time, I thought it might be a good idea to look at the science of composting so that I know what's happening inside the bin even though I can't see it.

Having looked at numerous websites, it would appear that there is more to it than just chucking stuff in a bin and waiting. There also seems to be vast differences in the time the process takes with some sites claiming that the process can be complete within 8 weeks whilst other experts advise that the process takes up to a year? So, how does it work and how long does it take?

The one thing that most sites do agree on is that composting is a highly scientific process and involves 3 distinct stages with each stage performing a vital function.

The first phase is the THERMOPHILLIC or HEAT stage.

When a compost bin is first filled, the microbes present begin to break down the organic matter and this process creates heat. As soon as the internal temperature of the bin reaches 45C it is said to be in it's thermophilic state. Only certain microbes (thermophiles) can work at high temperatures, other microbes will move away from the source of the heat and will remain dormant until the temperature drops. (The temperature can reach as high as 80C.)This heat then encourages the rate at which the organic matter is broken down by the thermophiles. It is important to allow a new compost bin to have 2 - 4 weeks at the initial thermophilic stage with 3 consecutive days of temperatures above 55C before turning the contents inside out. As the heat has been concentrated in the centre of the heap, it is unlikely that the materials towards the outside of the bin will have entered the thermophilic stage, therefore it is important to bring the material from the outside of the bin into the centre. Fresh material can also be added at this stage. This then allows another thermophilic stage to commence. As well as using heat to speed up the process of organic decomposition, it also effectively sterilises the organic matter by killing off some harmful microorganisms and weed seeds etc. A third thermophilic stage can be provoked by once again turning the heap inside out but generally this is not necessary and can cause more harm than good as the heat will eventually begin to kill off the good microbes thereby stalling the composting process altogether. For the impatient gardener it is possible to remove some of the partially broken down organic matter and add it to a worm farm at this stage. Composting worms are more efficient at producing worm cast from partially broken down organic matter.

The next phase is the MESOPHILLIC or WARM stage.

The mesophillic stage begins when temperatures within the bin fall below 40C. Initially the contents of the bin will fluctuate between the first 2 stages as the heat within the bin can change at different levels owing to the amount of oxygen present. When the bin has reached a constant temperature of 25C then the mesophillic stage has begun. It usually takes around 4 weeks from the last turning for the second stage to begin. During mesophillic stage the microbes which had become dormant throughout the thermophilic will rouse from their dormant state and will resume decomposition of the organic matter. As their work becomes complete and less organic matter is broken down, the temperature will drop again and once the constant bin temperature is around 10C it has reached the third and final phase.

The final phase - The Curing Stage.

Around 8 weeks after the bin is set up, the first 2 phases should be complete and now the broken down organic matter can be taken out of the bin and used as mulch. Alternatively, at this stage, larger organisms such as Tiger Worms can be introduced to get to work on the broken down organic matter turning it into more recognisable compost. The curing and maturation can take as long as necessary. The longer it's left then the more broken down it will become. Initially it will be possible to see what content was originally placed in the bin although the structures will have broken down significantly.

The other vital components for successful composting are oxygen and water. The microbes that work on our organic matter are all aerobic - oxygen loving. The more oxygen available, the harder they work. The harder they work, the greater the heat produced. The greater the heat, the faster the decomposition. Similarly, water is needed to stabilise the heat produced. If the contents of the bin are too dry then the heat will quickly rise above optimum levels meaning that most of the microbes are killed which will end decomposition. The moisture in the bin also helps the microbes to travel around from one area to the next which gives a more even result to the finished product. However, it's important not to let the bin become waterlogged as this will lead to a rotten product. The contents of the bin should have a similar water content to that of a wrung out sponge.

This method of composting is also referred to as batch composting. Once the bin has been filled, the process is allowed to work from beginning to end. This should lead to fresh, microbe and nutrient rich compost in under 3 months. However, if you continually top the bin up with new garden waste then the bin will struggle to reach and maintain the thermophillic stage which could mean that it takes up to a year to produce compost.

Day 4: Wednesday 23rd May 2012

So, after spending far too much of my working day reading about and researching the science of compost I came to the worrying realisation that the contents of our compost bin were too nitrogen rich 'green waste' and that we hadn't included enough carbon rich 'brown waste'. The only options were to leave it untouched and hope for the best or disrupt the process to add carbon and then hope for the best. The latter option won so I collected lots of dried leaves and cherry blossom along with twigs and some corrugated cardboard (which I made sure was thoroughly moistened) and took the top 5" of grass cuttings from the compost bin. I mixed the brown waste in to the bin before putting the grass cuttings back. Reassuringly, I noticed that the bin contents smelled fresh and sweet and the temperature was definitely on the increase.


Day 5: Thursday 24th May 2012


Much excitement and action today as the Tumbleweed compost tumbler arrived. It's basically an alternative to a traditional compost bin because the ability to mix the contents on an almost daily basis means that the process is shortened - well that's the theory! I guess that the proof of the pudding is in the eating, or rather the proof of the compost is in the tumbling!? Anyway, I set about following the assembly instructions (a bit tricky in places) but, after 20 minutes or so, the tumbler was ready. As the tumbler is a self contained unit, it's designed to live wherever is most convenient which is a great advantage to anyone who is less than keen on having an unsightly compost bin visible in their garden. The tumbler itself is large, standing around 4ft high yet it's capacity is the same as the, much smaller, compost bin - 220 litres.


The advantage of a tumbler lies in its internal structure, a stainless steel breaker bar running through the centre of the tumbler acts not only as the axle on which it spins but also speeds up the composting process by physically breaking down the organic matter.









As with the compost bin, the tumbler needs to be filled with a mixture of 'green' nitrogen producing fresh garden waste and 'brown' carbon producing dried waste like leaves, cardboard or even paper. So, we set about preparing the contents. All instructions for composting state that any dry matter like cardboard needs to be moist when added - I found that the easiest way was to fill the wheelbarrow with cardboard and give it a thorough soaking with the garden hose. The contents were then added to the tumbler.







Only time will tell if the tumbler IS quicker at turning garden waste into compost, the instructions say that it should take 4-6 weeks with the only on going maintenance being a few spins of the tumbler every couple of days.



Anyway, back to the compost bin....





When I checked the bin yesterday there was a noticeable reduction in volume and you could definitely feel the heat. Further investigation showed that the temperature in the centre of the bin was just over 50C so we've definitely entered the THERMOPHILLIC stage!!









Day 7: Saturday 26th May 2012

So the compost bin has been set up for a week now, the internal temperature has been in excess of 50C for the last 3 days and the volume has decreased dramatically. The instructions state that it is necessary to regularly aerate the contents of the bin to help the composting process, this can also trigger a second THERMOPHILLIC phase as the previously cooler contents are moved towards the centre of the bin.



Whilst aerating, I thought I could see steam rising from the compost bin but further investigation revealed that what I thought was steam was in actual fact a very fine powdery mould. This sent me rushing straight to Google where it seemed to be telling me that my compost was becoming anaerobic which isn't good. However, almost all of the other sites seemed to say that the mould would be accompanied by a foul smelling slimy mess neither of which can be said for my bin? And so the research continues....






Day 11: Wednesday 30th May 2012

After doing some more research into the presence of the powdery mould stuff coating the top of the compost bin, it seemed that the only possible conclusion was that the mix was becoming too anaerobic. So today i ditched the aerator and set to the compost bin with a garden fork. Although there is still definitely no unpleasant smell coming from the compost bin, i did see that the garden waste towards the bottom of the bin was significantly wetter than the top. Also, the compost hasn't really come back up in temperature since the weekend which probably indicated a lack of oxygen which is vital to kick start the composting process.I hope that i managed to catch the possible anaerobic situation fairly early on and so have been able to prevent the situation worsening.




After thoroughly mixing and turning the contents of the compost bin, i added a fine layer of compost conditioner which is recommended by Tumbleweed, the manufacturer of both the compost bin AND the compost tumbler. The conditioner is supposed to neutralise acidity within the compost and restore the pH balance to neutral. Along with the conditioner, i also left the lid off the bin for a few hours to allow the contents to breath, i didn't want to risk it with the rain so i replaced the lid before night fall! I'll check the temperature and the moisture level again tomorrow, hopefully the mix up will instigate another thermophilic phase.



I gave the compost tumbler a few spins as per the instructions and had a quick look inside. The volume does appear to have reduced but I'm still not too sure whether it will speed up the composting process or not. The breaker bar doesn't seem to be breaking much up and because the contents are regularly displaced i'm not too sure how, or even if, thermophilia will occur?


The last job of the night was to set up a secondary compost bin as per the recommendations in the Tumbleweed compost bin instructions. I haven't bothered with a detailed account as it should, in theory, work in exactly the same way as the existing bin.

Day 22: Sunday 10th June 2012

So, it's 3 weeks in to project: composting and it all seems to be going fairly well! For logistical reasons both of the compost bins have been moved slightly but it certainly doesn't seem to have caused any problems!

The original bin has now reduced in volume by well over 50% and has begun to turn a dark brown colour with virtually no green matter in sight. The powdery mould has vanished and the moisture seems pretty well controlled. The compost smells earthy and not at all unpleasant. By moving the bin it gave us the chance to thoroughly aerate everything which definitely makes a difference. There are still some twigs that haven't even begun to break down but then I don't think I expect them to.




By contrast, as the picture shows, the second compost bin is not working nearly as fast but we've been using this bin in a more traditional way regularly adding more garden waste. This means that it's not getting the chance to settle down and reach a high enough temperature to kick start the thermophillic bacteria into action. But, this isn't a bad thing as it will be interesting to see how long the process takes.






Finally after days and days of tumbling (and the odd lid-based mishap) the contents of the tumbler are also now showing signs of breaking down. Because of the sheer size of the tumbler and the fact that you need to leave room inside for the contents to tumble, you can't fill it to the brim so it doesn't get the chance to operate like a hotbox like the original Gedye compost bin did. For this reason the internal temperature hasn't risen much above 35C so it relies on the internal breaker bar and the presence of mesophillic bacteria to turn the garden waste into compost. The lid of the tumbler states that it is the Tumbleweed compost tumbler and mulch maker which makes me think that the end result might not be the rich crumbly compost that I'm expecting from the Gedye bin. Only time will tell but I'll be needing plenty of mulch to protect the garden over winter so that's not necessarily a bad thing.!
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