From Shell to Carbon: The Steam Activation Manufacturing Process Explained
Technical content reviewed by Sri Wahyuni, Head of Laboratory.
Last updated: June 2026
Coconut shell is one of the best raw materials for activated carbon: it is hard, low in ash, and rich in the tight micropores that drive adsorption. But the shell only becomes activated carbon after a controlled thermal process. This guide walks through how PT Karbon Aktif Indonesia converts raw coconut shell into high-activity activated carbon using the steam activation method — the same process that gives our products their high iodine number and hardness.
Why steam activation?
There are two main ways to activate carbon: chemical activation (using agents such as phosphoric acid or zinc chloride) and physical, or steam, activation. Steam activation uses only high-temperature steam and heat — no chemical residues — which is why it is preferred for food-grade, drinking-water, and gold-recovery carbon. It develops a predominantly microporous structure ideal for adsorbing small molecules.
The process, step by step
- 1
Coconut Shell Sourcing
NTT, Sulawesi, Sumatra, Java.
- 2
Carbonization
Shells converted to charcoal.
- 3
Steam Activation
High-temperature steam (~900–1000°C) develops the micropore structure.
- 4
Screening & Sizing
Graded to precise mesh sizes.
- 5
Quality Control
Lab testing: iodine, CTC, hardness, ash, moisture.
- 6
Packing & Export
25 kg bags / jumbo bags, containerized.
Carbonization: from shell to char
First, cleaned coconut shells are heated in a low-oxygen kiln. Without enough oxygen to burn, the shell instead pyrolyzes — volatile compounds are driven off and what remains is a rigid carbon skeleton (char) with a rudimentary pore network. This char is the feedstock for activation.
Steam activation: building the micropores
The char is then exposed to superheated steam at roughly 900–1000°C. At these temperatures the steam reacts with carbon atoms and etches out a vast internal network of pores, dramatically increasing surface area — a single gram can reach a surface area of over 1,000 m². Controlling temperature, steam flow, and residence time is what sets the final iodine number, CTC activity, and hardness.
Screening, quality control, and packing
After activation, the carbon is cooled, then screened and graded to precise mesh sizes for each application (for example 6×12 for gold recovery or 8×30 for water treatment). Every batch is lab-tested for iodine number, CTC, hardness, ash, and moisture before it is packed into 25 kg or jumbo bags and containerized for export.
What the key specifications mean
- Iodine Number (mg/g): Measures micropore surface area and overall adsorption capacity; the key general indicator of activity. Higher = more capacity for small molecules.
- CTC (Carbon Tetrachloride) Activity (%): Measures vapor-phase adsorption capacity; the governing spec for air and gas applications.
- Hardness / Abrasion Number (%): Resistance to mechanical wear; critical in gold recovery (≥98%) and any moving-bed, fluidized, or backwashed system. Low hardness means carbon losses and fines.
- Ash Content (%): Inorganic residue; lower ash = higher purity, important for food-grade and gold-recovery use.
Need steam-activated coconut shell carbon for your process?
PT Karbon Aktif Indonesia manufactures steam-activated coconut shell carbon in Central Java and exports worldwide. Request a spec sheet or a free sample.