All about charcoal & retorts

What is charcoal?
Traditionally charcoal is made from hardwood timber. The timber is heated to around 600-700C (1112-1292F) with the minimal amount or absence of air depending on whether it is being processed in a kiln or a retort. If there is too much air the wood will burn and turn to ash.

What can you make charcoal from?
Charcoal can be made from any organic material. Traditionally charcoal is made from large sections of wood, but it can also be made from twigs and branches, agricultural or garden waste and even animal bones and waste!

What is the difference between a retort and a kiln?
The difference is how the material to be charred is heated. A kiln heats the wood directly and a retort heats indirectly. In other words, with a kiln the wood is set alight and the air is restricted by banking up soil around the base of it, whilst in a retort the fire does not come into contact with the wood as it is sealed in a chamber so the air can not come in contact with it. A retort uses the smoke produced to help with firing, unlike traditional kilns.

What are the advantages and disadvantages of retorts?
The advantage of a retort is that it is easy to fire and there is very little risk of air getting to the wood during firing and turning it into ash. In a retort you can produce charcoal from any organic material where as in a kiln you can only use large section wood. This means that you can use a retort to make biochar out of very fine materials. The disadvantage of retorts is that they are more expensive to build and most larger retorts can not be moved very easily.

Why is the retort more environmental?
When charcoal is traditionally made the smoke is released into the atmosphere. Smoke contains particulates which have a negative effect on the environment and health. A retort burns up to 95% of the smoke it produces therefore not releasing particulates. Also the retort does not pollute the ground beneath it. When charcoal is made using a ring kiln tars soak into the ground. The tars produced in the retort form at the bottom to the chamber and can be scrapped out and disposed of safely.

How dry should the material to be charred be?
The material should ideally have a moisture content below 20% which you can measure with a moisture meter. You can make charcoal with a higher moisture content, but it will take longer to produce and take more wood to fire the retort. Leave the material to be charred stacked as long as possible and let nature do the work.

What quality of charcoal does the Hookway Charcoal Retort produce?
The carbon content is between 90-95%. A higher carbon content means that you will get more heat and less smoke from your charcoal. A good test for quality charcoal is the sound it makes. When you handle the charcoal it has a ring to it and sounds like a glass chandelier. A very high quality, high carbon charcoal like Binchochan (Japanese charcoal) sounds like two steel rods being hit together.

How much charcoal does the Hookway Charcoal Retort produce?
The retort will produce around 11kg (24lbs) of lumpwood charcoal.

How much wood does it take to fire the Hookway Charcoal Retort?
Depending on the moisture content of the material in the retort it will use from 7kg (15lbs) to 10kg (22lbs) of wood per firing. The retort needs to be fed with wood for the first hour or two, again depending on the moisture content, then the smoke produced catches light and finishes off the firing.

How long does it take to fire the Hookway Charcoal?
It takes 6-7 hours to fire and around 8 hours to cool. The length of time depends on the moisture content of material to be charred. A higher the moisture content will take longer.