12. Dec, 2020

Composting Bonfire Ash

Some allotment sites that had banned  bonfires over the summer, to avoid inconveniencing local householders who were at home and had their windows open to increase ventilation have now lifted the bans.  I am in favour of shredding and composting organic waste rather than burning it but if bonfires are being used the wood ash produced can be rescued and  composted.

Wood ash from bonfires of plant waste, hedge cuttings and pruning’s can be composted as can ash from  paper or cardboard and untreated and unpainted wood. It is not advisable to compost ash from bonfires that have included treated  or painted wood, synthetic materials, and plastic.  

 Wood ash is high in potassium, and contains phosphorous as well as manganese, iron, zinc, and calcium but the main feature in respect to composting is that wood ash is alkaline so it will reduce the acidity of the compost bins containing significant amounts of kitchen waste and grass mowings creating a better environment  for composting worms.  

However,  the quantity of wood ash added to the bin should be limited to a thin layer, or handful, every 6 inches (15cm). The ash should be carefully mixed or scattered so that it does not  clump, resulting in an  anaerobic  area within the bin. If substituting wood ash  for lime in one of the traditional composting layered system, it is about  half as effective as lime in neutralising acid.

It is best to avoid composting or collecting ash on windy days, when the ash is likely to be blown over the site and eye protection might be advisable .  Gloves should be worn as the  ash may cause skin  irritation.

If collecting wood ash for a community composting  site, or intending to store it, use  a  sealed metal  container, as the  nutrients are water soluble and hot ashes may melt  plastic.   Do not scatter wood ash over one of the site Reception bins.