16 Aug 2022

Hardwood Charcoal now on sale

Alex Summers

Our charcoal has been lovingly produced by our Estate Team from trees that have been removed as part of the sustainable management of our woodlands across the Botanic Garden and National Nature Reserve. 

Using an Exeter Retort Charcoal Kiln, our team processes seasoned hardwood to create charcoal which is perfect for use on the barbecue. The Exeter Retort is a specially designed kiln which looks a bit like a rudimentary steam train and is mounted on a trailer so our Estate Team are able to move it around the site to carry out a burn. 

The internal chamber of the Exeter Retort is tightly loaded with seasoned hardwood which will be turned into charcoal. At present we have predominantly been using Ash (Fraxinus excelsior) trees which we sadly have had to fell due to their demise from Ash Dieback fungus (Hymenoscyphus pseudoalbidus). Consequently the process of making charcoal also acts as a good biosecurity measure to kill the fungal spores within and on the wood to prevent them from spreading from the dead tree to healthy ones.

The external chamber is where we build a fire which spreads through the length of the kiln to heat the wood in the middle chamber. By heating up the wood in a low oxygen environment in the internal chamber, water and volatile gases are drawn out of the wood to leave charcoal which is a high carbon deposit. Due to its dense-carbon state, when charcoal is burnt it burns at a much higher temperature than wood which makes it perfect for cooking or use by industries such as blacksmithing.

Our Estate team monitor the progress of the charcoal burn using a digital thermometer linked to the internal chamber. Once the temperature here reaches 450 degrees Celsius a cap is placed onto the chimney of the charcoal compartment. This redirects the escaping volatile gases down into the firebox beneath where the gases ignite to further heat the internal chamber. This also reduces the gases which are being emitted into the atmosphere from the process. The design of the machine means that the burn can be completed within a working day which is much quicker than a traditional Ring Kiln. 

Throughout the year our team will be performing charcoal burns in the wider estate to demonstrate the practice to visitors, if you see them please come and say hello to find out more. All the wood comes from the National Botanic Garden as and when trees need to be removed for reasons of safety so our charcoal is truly locally-grown, harvested and processed. We are also looking into the use of crushed charcoal known as Biochar which has horticultural applications to improve the fertility of soils and also sequester carbon. We hope to sell this soon and also use it for scientific research within the Garden. 

Hopefully, you will enjoy our charcoal, pop into the Pot Blodyn garden centre, Gatehouse or gift shop to pick up a bag. Every sack contributes to the Garden’s conservation work and continued sustainable management of our National Nature Reserve.