Now that the burning of coal is being phased out in many countries as being a cause of climate change it is time to reconsider the use of the coal bunker. 

In the past it might have contributed to damaging the environment now it can work to help it by becoming a compost bin! 

Reusing an old concrete coal bunker as a compost bin is easy, it will already have a hatch original designed for removing coal but just  as suitable for remoing the finished compost, it will also have a removable lid and look at home in an urban garden.   

The Green Johanna is a hot composting system  which can be supplied with an insulating winter jacket. It is designed to cope with compostable waste from a family of five to eight and can deal  with a wide range of food waste including: bones, bread, cardboard, coffee filters, dairy products, eggshells, fish remains, fruit, meat, paper, tea bags and vegetables. plus, garden waste with  litter from my chicken hutch providing most of the browns. It is a good midrange bin that has been resistant to rats which have got under,  but never into, my two  bins  and to badgers on Stokes Wood Allotment  demonstration site. 

My bins at home tend to receive less attention than those on the allotment  but the top layers are mixed when fresh material  is added. As both bins are almost full, and mulch was need on the flower beds, where inherited ground cover fabric was being removed, I  decided to harvest the finished compost from both. 

So far, I have five trugs of compost  from the first bin with at least two more to come ....It must be a bit like the Tardis inside.

Compost  Safari

National Allotment Week a  National Allotment Society initiative,

8-14 August,

This year’s theme is Bugs, Bees and Broccoli  and we will be holding three Compost Safari sessions in Leicestershire so that children can discover  the minibeasts  that live in the compost bin and help in  the plant material and turn it into compost. Carry on Composting is offering three sessions run by a Leicestershire Master Composter

Tigers and Leopards in the garden

There will be the chance to discover  compost creatures  such as Tiger worms and Leopard slugs, earwigs  and worm eggs using magnifiers provided and photograph them using your mobile phone fitted with our lenses.

 Simple Compost extracts can be made in less than 20 minutes, making them very convenient if there is not enough time to brew aerated tea or to leave the compost for a long soak.   While the extract will contain a lower population of microbes  than compost tea made from the same compost it  has a longer shelf life. Aerated Compost tea only  has a shelf life of only 3-4 hours, while it is claimed that an extract has a shelf life of 1- 2 weeks. I recommend checking the smell of the extract before use to check that  it has not turned  anaerobic. If anaerobic  it will  have an unpleasant smell and should not be used

The extract will also contain the range of soluble nutrients found in the original compost. Extract nade wifrom compost produced from feedstock with a good C:N  ratio, when applied diluted 1:3, it has been shown to reduce growth of some weeds. so I would suggest using this dilution.  https://rodaleinstitute.org/science/articles/control-weeds-with-compo

Compost extracts require a larger volume of compost than teas. It is recommended to use about a kilogram  (or 3 cups) in 5 gallons of clean rainwater. It can be used as a soil drench, to boost the soil  round established trees on lawns  and even as a   root dip during  transplanting. Both the liquid and compost remaining in the bag makes a useful  activator added to  compost heaps. 

The Extract can be made agitating or vigorously mixing  compost in the water, or by running water at pressure through compost. I use sieved compost. The easiest method of doing this is to put the compost in a mesh screen bag, as would be used for making aerated compost tea. Put the bag in a container of clean rainwater and leave until the compost is soaked. I use a a 25l open container in which I have marked a 5gallon "fill-line" this gives plenty of room for mixing and makes it very easy to  ladel out to finished extract using a childs watering can.    Some recommended gently squeezing the bag so that the maximum number of microbes and nutrients are released.  The bag can be agitated for a few minutes so that the water washes through the compost. The bag is then left for another five minutes, and the agitation repeated.

If made in the “bag” it will probably not require filtering before use.

Overheating in Compost heaps has been identified  by some for as a possible cause of recent fires resulting from climate change It is true that  spontaneous combustion can occur in agricultural and horticultural situations  e.g., haystacks and large  compost piles. It can also  occur, very rarely, in domestic compost heaps.

In the UK most domestic composters use compost bins, rather than piles and the heat inside a compost bin can become hotter than in an open  compost pile as the bin will retain some of the heat generated by the composting process that will be lost to the atmosphere in an open pile. If the compost bin is stored in direct sunlight  the temperature will be increased.

If fresh “greens” e.g., grass,  are added to the bin the heat generated can be significant  and ignition may occur if dry material is added and not mixed or watered. The Mail online,  in July 2022, reported such a case where a bin fire damaged a house, and it was said by a fire officer that  grass cuttings had heated up during hot weather to such an extent that the compost  self-combusted.

Spontaneous Composting  in composting can occur at  temperatures of   150⁰C - 200⁰C which may result in  a  smouldering fire, this  can become to a traditional flaming fire if oxygen is introduced by aeration.

However, the risks are very small  in most domestic composting using  cold composting systems as the temperatures are normally at, or near, ambient.

 Higher temperatures are necessary to destroy pathogens and weed seeds and  “Hot composting” systems are designed to produce and hold the temperatures at  40-60⁰C with  temperatures of 76⁰C often reached for short periods.

“Smoke” can often  be seen rising from a compost heap,  but this is actually not smoke, but water vapor and the compost is  not smouldering. 

The measures necessary to reduce the risk are simply good management  and good composting. Keep the bin contents moist adding water when turning, adding additional materials and in hot weather.