How Charcoal Quality Is Measured: Ash, Fixed Carbon, Moisture

Photos do not tell you how charcoal burns — numbers do. Here is how charcoal quality is measured and how to read a spec sheet like a buyer.

When you compare charcoal, the marketing all sounds the same. The objective truth lives in a few lab numbers, reported on a Certificate of Analysis (COA). Learn to read these and you can compare suppliers fairly and predict how a charcoal will actually perform.

Proximate analysis: the four core numbers

• Fixed carbon (%) — the pure carbon that delivers heat. Higher fixed carbon means more, longer heat. This is the headline quality number for cooking charcoal.
• Ash content (%) — the non-combustible mineral residue left behind. Lower is better: less ash means cleaner burning and less to clean up.
• Volatile matter (%) — gases released as it burns. Lower volatile matter means less smoke and flame.
• Moisture (%) — water in the charcoal. Lower moisture means easier lighting and more usable heat per kilo.

Calorific value

The calorific value (heat energy per kilo, often in kcal/kg) summarises how much heat the charcoal can deliver. High fixed carbon and low moisture push it up. It is the best single figure for comparing the raw heat potential of two charcoals.

What good numbers look like

Exact targets vary by product and use, but as a general guide for quality cooking charcoal:

Ask the supplier for their actual figures for the specific product. A real manufacturer will share them; a reseller often cannot.

How the testing is done

These figures come from proximate analysis in a lab: samples are weighed, dried, and heated under controlled conditions to separate moisture, volatile matter, fixed carbon and ash. Independent labs (and the manufacturer’s own QC) run these tests and report them on the COA for a given batch.

Why these numbers matter to a restaurant

• Heat & burn time — high fixed carbon and calorific value mean a hotter, longer fire and fewer refuels.
• Smoke — low volatile matter keeps the air clean for guest-facing grills.
• Mess & labour — low ash means less cleaning during service.
• Consistency — stable numbers batch to batch mean every service cooks the same.

Reading a spec sheet like a buyer

Put two COAs side by side and compare the same properties. Be wary of a “spec” with no source or one that never changes batch to batch (a sign it is copied, not tested). Then confirm with a free sample burned in your own kitchen — numbers plus a real burn test is the complete picture.

For what these mean per product, see the coconut-shell briquettes guide and rubberwood briquettes. The COA is also one of your import documents.