How much coconut shell does one tonne of activated carbon need?

The answer, with the arithmetic

One tonne of finished coconut shell activated carbon needs 5.0–5.5 tonnes of raw shell at 12% moisture. That figure comes from two yields multiplied together: carbonization converts shell to char at 28–32%, and activation converts char to finished carbon at 60–65%. Take the midpoints — 30% and 62.5% — and you get 18.75% overall, which is 5.33 tonnes of shell per tonne of carbon.

If you buy charcoal instead of raw shell, the number is much smaller and much more reliable: 1.6–1.75 tonnes of char per tonne of carbon, because the carbonization yield has already been absorbed by your supplier.

Why your supplier quotes a different number

Three reasons, and all three are worth checking. First, moisture basis: a yield quoted on wet shell at 20% moisture looks 8% better than the same yield quoted dry. Second, iodine value: a 900 mg/g product genuinely needs less burn-off than a 1,050 mg/g product, so the yield is higher — comparing yields at different specifications is meaningless.

Third, and most commonly, the number refers to char rather than shell. A supplier quoting 1.7 tonnes per tonne of carbon is quoting char feed, not shell. It is not dishonest, but it makes the two proposals incomparable, and it is the single most common source of confusion in equipment tenders.

What it means for line size

At 5.33 tonnes of shell per tonne of carbon, a 1 t/h line needs 5.3 t/h of shell, or about 128 tonnes a day. That is 38,000 tonnes a year at 300 days — a volume that most buyers underestimate when they start planning, and the reason so many projects begin with purchased charcoal and add carbonization two or three years later.