The compost 4 bin system

 The 4 bin system and how I finally solved the compost problem.

Many years ago we started composting with one plastic bin, the type with a lid but no bottom which simply stood on the bare ground. It was just somewhere we could chuck and forget kitchen waste and feel we were green at the same time. Eventually the day came when the bin was full.  The top of the bin was full of fresh potato peelings but I harboured hope that underneath would be some wonderful friable compost. To reach this I had to put aside the top of the bin to find some semi-rotted slimy muck which I couldn’t persuade anyone to use and my wife promptly popped over to the garden centre to buy a couple of bags of beautifully graded and friable compost that was a joy to run through your fingers.

I should mention at this point that I am not a gardener and never have been. I do the composting and a bit of weeding but my wife and son do all the planting and make all the decisions.

I realised that our compost would need longer in the bin to  rot down fully so I bought a second bin that could be filled while the first continued to rot down.

A quick google taught me that good compost could be speeded up and improved by regular turning to introduce oxygen that was essential to breaking down the organic matter. Trying to turn the compost by forking it from the top of the bin was hard work and it was impossible to reach anywhere near the bottom. I soon realised that the turning problem could be solved by forking the compost from one bin to the other. So instead of alternating the active bin, I decreed that all waste go in one bin and when it was full I would fork the contents to the second bin. In practice I would lift the bin off the contents (remember it has no bottom) and place it to the side, leaving a pile of mixed compost. The top, which had barely started rotting, I would fork into the now empty bin by the side. The bottom now semi rotted I would fork into a barrow and wheel across the garden to the original bin where it would continue to mature. This was an extremely tiring and slow process and I dreaded the days when the fresh bin was full.

I muddled on with this system for several years and I produced some lovely compost but it didn’t look nice (full of twigs and egg shells) and I could never persuade the gardeners in the family to use it so I ended up just spreading it on any bear ground I could find, and we continued to buy supermarket compost for all our planting. 

Eventually salvation came from my neighbour. He had bought himself 2 lovely compost bins that he had never used and decided he no longer wanted, Would I like them? 

It happened that I had just cleared an area of overgrown hedge back to the boundary fence and it was the perfect location to site all 4 bins in a row. The 2 new bins were the largest and stood on the left. My original bin was the smallest and stood on the right with my other bin between them. I now had 4 bins in diminishing size from left to right, like the John Cleese and Two Ronnies sketch “I know my place”. Fresh kitchen waste goes in the first bin on the left, and usable compost is taken from the 4th bin on the right. It is important to start in the largest bin and finish in the smallest as the compost reduces in volume as it rots.

We now compost almost everything including straw from the pet rabbits, used grain from our home brewing, newspapers, sawdust, ash from the woodburner and the contents of the dustpan and vacuum cleaner. This last item is controversial. Whilst household dust is full of good organic material like hair and dried skin, it also contains a lot of micro plastics and man-made fibres like nylon and polyester. My gut feeling is that adding microplastics to the soil does no harm to plants or the organisms living in the soil. It simply acts like the grains of sand and silica that are already there. I could be wrong, and I know that eventually soil will be washed into the sea but this is ultimately no different than adding it to landfill and the beneficial organic material would be lost to the garden. So until someone convinces me otherwise I will continue to compost the contents of my vacuum cleaner and dustpan.

As a green woodworker I produce an abundance of wood chips and shavings. The saw dust and smaller wood chips go in the compost but the larger wood chips and shavings are dried and then make perfect fire-lighters for the wood burning stove, and ultimately find their way to the compost bin via the ash pan.

Whenever the first bin is full, normally every 6 to 8 weeks, the whole operation is a delight and takes less than an hour. First empty the contents of the forth bin, if it is not already empty, into a trug for general potting use. Then fork the contents of the third bin into the forth, the second into the third and the first bin into the second. All compost gets turned 3 times during the end to end process which takes about 6 months.

The final product still contains some twigs and larger unrotted lumps but my son uses a sieve to grade the compost and tips the larger pieces and worms back into the first bin. Also seeing what comes out of the end of the process may encourage him to chop some of the more woody waste before it starts the process.

An essential element of the process is a good worm population to help break down the organic matter. I am told you can buy worms to put in your compost but they have never been a problem for me, my bins are always jammed full of worms.

Readers of a sensitive disposition should probably stop reading now before I add the final refinement to my system. As I mentioned earlier, I spend alot of my time doing woodwork in my workshop at the bottom of the garden. Whenever I am taken short, rather than return to the house for a pee, I use an old tin which I then tip into the first bin which helps to break down the organic material and adds moisture and nitrogen to the compost. I’ve not asked if the worms like this but they appear to thrive. It certainly doesn’t add to the smell.