With the coming of winter most composting processes slow down or stop as a result of the cold weather but there is no reason to stop feeding the compost heap or bin in preparation for an increase in microbial
activity when spring eventually puts in an appearance. However you may like to try to keep the composting process working over the winter to increase your yield and as a challenge to show your composting skills.
The use of a commercially
available insulated bin, such as the Hotbin or Biolan, will mean that while the composting process may slow a little it should continue during the cold weather.
Alternatively with a little work ordinary bins can be insulated so that they continue
the composting process over the winter months. If you continue feeding the heap or bin with the right mixture of greens and browns the rotting process will continue generating its own heat all that is required is that as much as possible of the heat is retained.
One of the keys to success is the size of the bin, or heap, it needs to be at least 1 cubic metre (1.3 cu yards) to provide the critical mass for thermophilic organisms to keep working. Unless insulated to a very high standard a smaller bin or heap
is likely to be frozen while one that falls to near freezing will not remain active. The first approach to prolonging the working period is therefore to increase the size of heap to encourage the composting process continues longer into the winter season.
It will also be advisable to site the heap or bin so that it is in full sun to take advantage of any external heat.
Covering the compost heap with a tarpaulin or carpet avoids it becoming waterlogged with cold rain and may slow the
loss of heat generated but this is not enough to keep the bin working, insulation is necessary to keep the bin functioning during the colder months.
Old carpet, flattened sheets of cardboard or polythene
sacks filled with straw or loft lagging ( sealed in a plastic bag to keep it dry) or layers of bubblewrap will help retain the heat if wrapped round a plastic bin or wormery.
Wooden bins can be lined with layers of corrugated cardboard with a
layer of polythene (old compost bags?) on the inside where the cardboard would come into contact with the compost. One of the points to be considered when buying or making a wooden bin is whether to opt for solid or slatted sides. The slatted slides offer
improved aeration during the summer but are more difficult to insulate during the winter. Bales of straw or hay can provide a quick and easy means of insulation but will some need to be removed to allow waste to be added to keep the composting process
working though the winter. An outer wall about six inches bigger than the original sides can be built of wood or blocks round the bin, to provide a space for further insulation to increase heat retention. Wall insulation material is excellent,
as is loft insulation but items such as cardboard or bubble wrap can also be used. If a pallet bin is being converted cardboard or other insulating material can be stuffed in the gaps in the pallet to further increase the insulation
The top of the bin
must also be insulated. Some sources suggest using a thick layer of bedding, loose straw or leaves, while these will help retain the heat they are not practical if waste food material is to be added to the bin during the winter. A layer of loft or wall insulation
sandwiched between wooden boards from pallets or polythene sheeting cut slightly larger than the top of the bin and sealed to keep the insulation dry provides an insulated lid that can be easily removed
composter reports that they live off-grid in Colorado at 9,200 foot elevation where the gets very cold cold. (Lows in the n -40s, with negative teens being the high for a few weeks at a time.) He prevented his worm bin freezing by filling it 3/4s
full of bedding, (i normally dont go over 25%) and then added lots of food to one side. The bin was then put in the middle of a a base of 9 straw bales with the bin in the middle, and then built a "cabin" around them using about 15 more bales.
It worked out great, and in the spring the straw to was used to mulch the garden