Shell or wood charcoal as feedstock: ten points to compare

When an activated carbon maker picks a starting material, the shortlist often comes down to coconut shell charcoal or wood charcoal. Both are charcoal, both can be activated and both are sold in bulk, so the choice is easy to get wrong if it rests on a label. This note sets out the points on which they usually differ, says which ones are well documented and which are not, and lists what to ask each supplier. It does not claim that one is better. The answer depends on the carbon you intend to make.

A word on the evidence

The general differences below are the ones commonly described in trade and technical sources. They describe tendencies, not guarantees: a poor shell charcoal can be worse than a good wood charcoal. Nothing here is a Kora test result. Kora publishes only three limits for its shell charcoal, and the page for it shows what is missing.

Where they usually differ

1. Density. Coconut shell is a dense, compact material. Wood is generally less dense and varies a great deal with species. Density affects how much fits in a vessel and how the charcoal behaves in the kiln.

2. Hardness. Shell-based charcoal tends to give hard grains, and this is the reason it is commonly named as a starting material for grades that must resist wear, such as those used in gold recovery. Wood-based material tends to be softer. Hardness is measured on the finished carbon, so ask for the figure and the method rather than relying on the reputation of the raw material.

3. Pore tendencies. Shell-based carbons are commonly described as rich in fine pores, which suits small molecules and gases. Wood-based carbons are commonly described as having more large pores, which suits large molecules such as colour bodies. These are tendencies of the material. The activation you apply changes them a great deal.

4. Ash. Ash comes from the mineral in the starting material and ends up more concentrated after activation. Shell tends to be lower in ash than many woods, but species, soil and handling matter on both sides. Ask for the ash figure per lot and whether it is dry.

5. Consistency. A shell is a standard part of one plant. Wood can be many species and mixes. A supplier of wood charcoal should tell you what species go into a lot, and a supplier of shell charcoal should tell you how the shell is selected and cleaned.

6. Purity of the raw material. Fibre, soil and other debris mixed with shell show up as ash and as weak grains. Ask about the removal of fibre and sand before carbonising.

7. Supply. Shell is a by-product of coconut processing, so its supply follows the coconut industry. Wood supply follows forestry and other uses. Ask where continuity risks sit for the volume you need.

8. Size and form. Charcoal can reach you as lumps or as powder. Size spread, not just the average, decides how well a line runs. Ask for the spread and for how it is measured.

9. Volatile matter and carbonising conditions. How the charcoal was made, at what temperature and for how long, changes its volatile matter and how it activates. Two charcoals from the same raw material can differ more than two from different ones. Ask for volatile matter per lot.

10. Handling and shipping. Charcoal needs proper packing and paperwork, and sea transport rules for it have been changing. Ask the supplier how the cargo is classified, and check with your forwarder.

What Kora publishes about its shell charcoal

Kora publishes a fixed carbon limit, a moisture limit and an ash limit for its lump shell charcoal, plus a moisture limit and a made-to-order mesh for its powder. It does not publish volatile matter, hardness or size spread. The shell charcoal for activation page shows each of these rows and says which are empty. That is the starting point, not a final specification.

How to run a fair comparison

• Ask both suppliers for the same list of properties, in the same form.
• Request a sample of each, with the laboratory report of the lot it came from.
• Activate both on your own line under the same conditions, and compare the grade sheet figures you care about.
• Compare cost per tonne of finished carbon, not cost per tonne of charcoal. Yield after activation changes the answer.

Ask us

If you are weighing shell charcoal or wood charcoal and want to know what Kora can supply and state, write through the contact page. Give the carbon you plan to make, the form of charcoal you need and your usual volume. We reply within two business days, and we say plainly when a question is outside what Kora supplies.