Bio Char

This week we had our first fire of Winter. A bit later than usual, but then the days have been warm and the nights mild. We benefitted from the excellent insulation of our house and made sure we closed up and drew curtains early in the afternoon to retain the warmth. Then finally some rain came and everything cooled just that extra few degrees.

The by-product of having a wood heater is that there is plenty of ash during the cold months. Which is handy spreading around the garden. Pure wood ash consists of calcium, potassium and magnesium. Because it contains calcium it will raise the pH of the soil, and can be used on acid soils instead of lime. Here and here is some further information.

But there is another by-product. Just before we go to bed we dampen the fire by turning down the air slide which slows the burning. The next morning there is always a reasonable amount of charcoal remaining on and in the white ash.

The morning after

Bio Char is charcoal that has been burnt in a low oxygen atmosphere. Therefore every morning the  firebox is cleaned out and the material stored in a metal container. Sometimes the charcoal is still smouldering hence the metal container. This process also causes whatever remaining charcoal to be buried in ash which limits its Oxygen.

After it has cooled it is emptied into a feed bag for storage. By the end of Winter there is usually half a dozen bags of this material. The charcoal pieces can be quite large and to break them down they would be sieved through some bird wire which has holes about 12mm diameter and then the larger bits placed in a metal drum and pulverise with the end of a large piece of wood (3 x 2).

This was time consuming and time was in shortfall. The solution was the Chipper/Mulcher. Extremely quick but messy as a dust cloud spreads for about 5 metres around the work area. Not something to do next to the laden clothesline. And a good face mask compulsory.

The end result was that with minimal effort there was 120-150 litres of Bio Char and wood ash.

Whenever compost is being made this mix of Bio Char and ash is sprinkled lightly every few layers.