Charcoal burning

Charcoal burning was traditionally big in the iron industries of the Weald, Forest of Dean, Lake District but is now practised widely as a part of woodland management.

Until well into the twentieth century, charcoal was made mainly using earth burns or earth clamps, but kilns and retorts were developed in the seventeenth century and have now taken over except for historical re-enactment. Recently a new generation of charcoal retorts have been favoured as being more efficient conversion of timber to charcoal than kilns (and far better than clamps) and less polluting.

Charcoal is made for a variety of purposes, including for drawing, tandoori ovens, animal feeds, filtration, and charcoal fines for biochar/soil improvement.

Historically, two primary techniques have dominated the craft, the traditional Earth-Mound Kiln and the more modern Metal Ring Kiln.

The Earth-Mound Kiln:

This is the oldest method, used for millennia by ‘colliers’, which requires immense skill as the burner cannot see inside the structure and must judge the progress based on the colour of the smoke.

A central chimney (the ‘fagan’) is built using three stakes. Logs are then stacked vertically around it in layers to form a dome. The stack is covered with a layer of ‘browns’ (dry leaves or grass) and then sealed with a thick layer of damp earth or turf to make it airtight. Burning embers are dropped down the central chimney to ignite the heart of the stack. The burner then manages ‘vents’ at the base to control the airflow. Heavy steam indicates the water is leaving, and thin blue smoke indicates the wood is carbonising. Clear or no smoke means the wood is beginning to turn to ash and the vents must be sealed immediately.

The Metal Ring Kiln:

Most modern craft charcoal in the UK and Europe is produced this way, being faster and more forgiving than an earth mound.

A large steel cylinder is placed on the ground, often supported by several inlet flues (chimneys) at the base. Wood is packed tightly inside and a ‘lighting point’ of dry kindling is usually placed at the bottom. Once lit, the lid is placed on top. The fire draws air from the base, but as the heat rises, the gases are forced back down and out through the external flues. This ‘reverse draught’ ensures even heating throughout the kiln. Once the smoke turns a specific electric blue colour, the chimneys are removed and all inlets are sealed with sand or soil to cut off oxygen completely, allowing the charcoal to cool.

• Willow charcoal for artists
• Biochar – used as a soil improver and as a method of carbon capture within soil

• Market issues: Cheap imports of charcoal from unsustainable sources tend to keep UK prices down. Many UK makers cannot afford to sell it at the same price as imported charcoal.

• National Coppice Federation
• The National Coppice Federation produces guidance for charcoal producers in the UK
• The Royal Forestry Society
• The Hampshire Coppice Group

As of January 2025, the Coppice Products website lists 54 makers of charcoal and bio-char, although the output of each maker is not known.

A list of local coppice groups can be found on the National Coppice Federation website