As the temperature outside plummets so the compost in your bin might cool down, but by maintaining good composting techniques you can keep your compost ‘cooking’ even in the coldest winter periods.

In the case of the Green Johanna, adding the insulating jacket also helps.

The Johanna pictured below in January in Leeds kept its compost warm at 40 degrees Celsius while the ground temperature was at zero.

This particular Johanna received all food waste from a family of four, rising to 10 people over the Christmas period. Carbon sources include stored shredded leaves from several trees in the vicinity, as well as Christmas paper waste such as cardboard packaging, compostable wrapping paper and Christmas cards.

The Great Green Systems team tend to keep the jackets on our Green Johannas for most of the year, not just in winter, as we’re based in the chilly north of England.      

Don’t worry that using the jacket will make the Johanna too hot for worms, as one customer suggested. This is not a problem because worms can easily enter and leave the composter through the small holes in the base plate. At temperatures approaching 30 degrees Celsius they will move where it is cooler, usually the bottom of the bin where the compost is maturing, or they can leave the bin entirely.

 The jacket is made from foamed polyethylene – a lightweight, water-resistant material that is tough but flexible and designed to fit snugly to prevent cold air from circulating round the Johanna. It’s made for Great Green Systems by a specialist foam manufacturer in Northamptonshire.

When fitting the jacket, it’s important to ensure that the bottom section doesn’t cover the vents at the sides of the Johanna’s base as these are necessary for airflow.  

The jacket should be installed with the two upper sections pulled down so they overlap the section underneath by about 5 cm. Doing this means the ventilation holes are left clear.

 Also check throughout autumn and winter that the vents at the bottom of the Johanna are not blocked by leaves or debris or snow. Air is taken in at ground level so keep this area clear so that air can enter freely.

The jacket can easily be removed if the compost gets too hot (above 70 degrees C) in warm weather. Compost thermometers, which have a stem to reach down into the compost, are a useful aid.    

• TIP: Give the bin’s contents a boost by adding beneficial bacteria in bokashi bran or a layer of soil or mature compost. You can also add coffee grounds or chicken manure to add a hit of nitrogen to your mix.  

Johanna planner for winter:

• In freezing weather limit ventilation through the Green Johanna lid’s ventilation system – twist the lid towards the minimum setting.
• Wood chips are a great addition, creating airflow and adding plenty of fungi to the bin.

• Keep adding to the bin – ideally about three times a week – to maintain the composting process. The Johanna’s generous 330 litre capacity means the compost mass acts as an insulating factor. 
• Chop items up. Smaller items provide a larger surface area for more microbes to work on. 
• Aerate regularly – about twice a week – to ensure the aerobic microbes breaking down the waste get enough air.  Without air, the contents will turn anaerobic and start to smell.   
• Check moisture levels – by doing the squeeze test; grab handfuls of the bin’s contents and squeeze. One or two drops of liquid should appear. The ideal consistency is like a wrung-out bath sponge.