50–70% (50–70% moisture)

50–70% is the moisture content of the solid fraction recovered when raw digestate (80–95% moisture) is mechanically dewatered by a screw press or decanter centrifuge in an Indian CBG plant. The lower end (50–55%) reflects centrifuge output; the higher end (65–70%) reflects simple inclined screw presses, which are cheaper but produce wetter solids. Either way, the material is now stackable, transportable in a tipper truck, and no longer pourable as a slurry.

At 60% moisture, 1 tonne of separated solids contains 400 kg of dry matter and 12–20 kg of NPK, yielding 3–4× the nutrient density and roughly half the freight cost per kg of nutrient compared with raw digestate. The fraction also concentrates phosphorus (which binds to solids) and organic carbon (lignocellulose), producing material well suited for composting or further drying to 10–15% for pelletisation. The complementary liquid stream — 95–98% moisture and 65–75% of original mass — carries most of the ammoniacal nitrogen and potassium and is typically used for on-farm fertigation or returned to the digester as inoculum dilution water.

Operational trade-offs at 50–70% moisture are predictable. The material is still wet enough to attract flies, smell strongly within 24–48 hours, and lose nitrogen by ammonia volatilisation if stored uncovered — typical losses of 5–15% per week. Indian plants therefore move the solid fraction directly into windrow composting (which intentionally drives off some moisture) or rotary dryers using CHP waste heat. Storage of the wet solid for more than 5–7 days requires covered or in-vessel composting, which adds ₹15–30 lakh of capex but cuts nitrogen losses to under 3%. The economic optimum for most 10 TPD plants is to dewater, compost in-vessel for 14–21 days, dry to 12% moisture, and pelletise — a four-stage line that converts a ₹200/tonne nuisance into a ₹6,000–10,000/tonne FCO-registered fertilizer.

• Typical moisture content of digestate solid fraction after screw press (60–70%) or centrifuge (50–55%).
• Concentrates dry matter and phosphorus 3–4× versus raw digestate; doubles nutrient-per-tonne for freight.
• Storage above 5–7 days uncovered loses 5–15% of nitrogen per week as ammonia.
• Standard downstream route: composting + drying + pelletising to reach ₹6,000–10,000/tonne FOM sale.