Application Guide
Activated Carbon for Biogas Purification
H2S removal, siloxane adsorption, carbon selection, and sourcing from China.
Biogas contains H2S, siloxanes, and VOCs that damage engines, turbines, and upgrading equipment. Activated carbon is the most common removal method. The tricky part — one carbon type doesn't handle everything.
We supply carbon to biogas plants in Europe, Southeast Asia, and South America. Here's what works and what doesn't.
Carbon Types for Biogas
| Contaminant | Carbon Type | Mechanism | Capacity | Price FOB |
|---|---|---|---|---|
| H2S (<500 ppm) | KOH impregnated pellet | Chemical | 0.15–0.20 g/cc | $1,800–2,200/ton |
| H2S (>2000 ppm) | KI impregnated pellet | Catalytic oxidation | 0.20–0.30 g/cc | $2,500–3,500/ton |
| Siloxanes | Virgin coal-based pellet | Physical adsorption | 5–15% by weight | $1,000–1,500/ton |
| VOCs / Mercaptans | Virgin coconut shell GAC | Physical adsorption | Varies | $1,500–2,200/ton |
| H2S + light VOCs | NaOH impregnated pellet | Chemical + physical | 0.12–0.18 g/cc | $1,600–2,000/ton |
1. H2S Removal: Impregnated Carbon
H2S is the primary concern. Concentrations range from 100 ppm (well-managed digesters) to 10,000+ ppm (landfill gas).
Low-to-medium H2S (100–2000 ppm): KOH or NaOH impregnated pellet carbon. The alkaline impregnant reacts with H2S to form trapped sulfur compounds. 4mm pellets preferred for lower pressure drop.
High H2S (>2000 ppm): KI impregnated carbon. Catalytic oxidation converts H2S to elemental sulfur. Higher capacity but costs 40–60% more than KOH.
Key specs to request: H2S breakthrough capacity (g/cc), impregnation % (typically 5–15%), CTC value, hardness (>90%), moisture (<5%).
2. Siloxane Removal: Virgin Carbon
Siloxanes come from personal care products in wastewater sludge. When burned, they form silicon dioxide deposits that destroy engine pistons and turbine blades. Repair costs: $50,000+ per incident.
Virgin coal-based carbon with high surface area (>900 m²/g) and developed mesopores works best. Coconut shell has too many micropores — siloxane molecules are too large to fit.
Key specs: BET >900 m²/g, iodine >900 mg/g, CTC >55%, 4mm pellet or 4×8 mesh.
3. Two-Stage System Design
Stage 1 — H2S removal: Impregnated carbon bed. Replaced every 3–6 months. Sized based on H2S loading.
Stage 2 — Siloxane polishing: Virgin carbon bed. Lasts 6–12 months because Stage 1 handles the heavy lifting.
Some plants add a third stage for mercury or chlorinated compounds. For most biogas-to-energy applications, two stages are enough.
4. Pellet vs Granular
| Factor | Pellet (4mm) | Granular (4×8) |
|---|---|---|
| Pressure Drop | Lower ✅ | Higher |
| Flow Distribution | More uniform ✅ | Can channel |
| Dust | Less ✅ | More |
| Price | 5–10% more | Baseline |
| Verdict | Preferred for biogas ✅ | OK for small systems |
5. Sourcing from China
China produces a large share of the world's impregnated carbon. Main regions: Shanxi (coal-based) and Fujian/Hainan (coconut shell). For biogas, coal-based pellet carbon from Shanxi is most cost-effective.
Verify before ordering:
- H2S breakthrough capacity — ask for test report, not just spec sheet numbers
- Impregnation uniformity — poor impregnation means some pellets work, others don't
- Hardness after impregnation — the process can weaken carbon structure
- Packaging — 25kg bags on pallets or 500kg/1000kg super sacks
- Shelf life — use impregnated carbon within 12 months of production
Our Biogas Product Line
- KOH impregnated 4mm pellet — H2S capacity 0.15–0.20 g/cc, standard biogas
- KI impregnated 4mm pellet — H2S capacity 0.20–0.30 g/cc, high-H2S landfill gas
- Virgin coal-based 4mm pellet — iodine 900+, CTC 60+, siloxane removal
- Custom impregnation: NaOH, KMnO4, sulfur, etc.
MOQ: 10 tons for impregnated, 20 tons for virgin. Samples available.
Need Carbon for Your Biogas Plant?
Tell us your H2S concentration, flow rate, and current carbon type. We'll recommend the right product and send samples.
Frequently Asked Questions
What type of activated carbon removes H2S from biogas?
Impregnated activated carbon — KOH or NaOH impregnated pellets for low-to-medium H2S (100–2000 ppm), KI impregnated for high H2S (>2000 ppm). The impregnant reacts chemically with H2S, which is why virgin carbon alone doesn't work well for this.
How long does activated carbon last in a biogas system?
For typical biogas with 500–2000 ppm H2S, impregnated carbon lasts 3–6 months. Virgin carbon for siloxane removal lasts 6–12 months. Replace at 80% breakthrough. Actual bed life depends on concentration, flow rate, humidity, and temperature.
Can one carbon type remove both H2S and siloxanes?
Not effectively. H2S needs impregnated carbon (chemical reaction), siloxanes need high-surface-area virgin carbon (physical adsorption). Most plants use two stages: impregnated first for H2S, then virgin for siloxanes.
What does biogas-grade activated carbon cost?
Virgin coal-based pellet: $1,000–1,500/ton FOB. KOH impregnated pellet: $1,800–2,500/ton FOB. KI impregnated: $2,500–3,500/ton FOB. Coconut shell options cost 20–30% more.
Pellet or granular for biogas?
4mm pellets are preferred — lower pressure drop, more uniform flow, easier handling during replacement. Granular works for smaller systems but creates higher pressure drop in tall beds.
What is the MOQ for biogas carbon from China?
Standard: 1 FCL (20 tons). For impregnated carbon, some manufacturers accept 10-ton minimums. We ship LCL (1–5 tons) for first-time buyers testing our product.