Pelletized (pelletised digestate)

Pelletized describes organic material that has been converted to dense, uniform cylindrical pellets — typically 6–10 mm diameter, 15–25 mm long — by mechanical extrusion through a steel die under high pressure (150–300 bar). For Indian CBG plants, pelletised digestate is the highest-value form of the fertilizer output: bulk density of 600–700 kg/m³ (versus 200–300 kg/m³ for loose compost), moisture content of 10–15% (stable for 6–12 months), and physical form compatible with standard fertilizer spreaders and 50 kg woven bag distribution.

The transformation from raw digestate (90% moisture) to finished pellets involves a four-stage line: dewatering by screw press or centrifuge to 60–70% moisture, drying in a rotary or belt dryer (using CHP waste heat where available) to 10–15% moisture, grinding in a hammer mill to below 4 mm particle size, and die-press extrusion at 150–300 bar with steam conditioning at 70–85°C. Total processing energy is 800–1,200 kcal per kg of water removed plus 30–60 kWh of electrical demand per tonne of pellets produced. Plant capex for a 2–5 TPH line lands at ₹80 lakh–2 crore.

The commercial uplift is substantial. Raw digestate sells at ₹500–1,500 per tonne if at all; composted FOM at ₹3,500–6,500 per tonne; pelletised FOM at ₹6,000–10,000 per tonne. A 10 TPD CBG plant processing 30 tonnes of digestate per day into roughly 4–5 tonnes of pelletised FOM generates ₹25,000–50,000 per day of additional revenue beyond gas sales — payback on the pellet line is typically 18–30 months. Pelletisation also unlocks national distribution: shelf life beyond 6 months and freight-cost competitiveness extend the market radius from 25 km (raw) to 500–800 km (pellets). FCO 1985 (amended 2021) treats pelletised FOM as a distinct grade requiring 12% maximum moisture and 1.2% minimum N + P + K on fresh basis.

• Dried, ground, and extruded into 6–10 mm cylindrical pellets at 600–700 kg/m³ bulk density.
• Four-stage line: dewater, dry, grind, extrude — total capex ₹80 lakh–2 crore for 2–5 TPH.
• Sale price ₹6,000–10,000/tonne; payback on the line typically 18–30 months on a 10 TPD CBG plant.
• Shelf life 6–12 months at 10–15% moisture; market radius extends to 500–800 km.