Anaerobic Digestate (Digestate)
Also known as: biogas digestate · AD digestate
Anaerobic Digestate is the nutrient-rich organic residue remaining after organic waste is processed in a biogas digester — a valuable organic fertiliser sold as a secondary revenue stream from CBG plants.
Last updated
Beyond definitions
Planning to start a CBG business?
Get the full business understanding — capex, regulations, machinery, vendor questions, and risk checks before you commit capital.
What is Anaerobic Digestate?
Anaerobic Digestate is the nutrient-rich, partially stabilised slurry that remains in the reactor after methanogenic bacteria have converted the biodegradable fraction of organic feedstock into biogas. In Indian SATAT-scheme CBG plants, raw digestate exits the reactor at 90–95% moisture, neutral pH (7.0–8.0), and contains the bulk of the original nitrogen (60–80% retained, as ammonium), almost all of the original phosphorus and potassium, and stabilised humic-like organic matter that improves soil structure.
Compositionally, digestate from a typical Indian CBG plant runs 1.5–4% N, 0.5–1.5% P₂O₅, and 1.0–3.0% K₂O on dry basis — meaningfully higher than raw FYM because anaerobic digestion concentrates nutrients while destroying about 40–60% of the feedstock's volatile solids. The nitrogen is largely in ammoniacal (NH₄⁺) form, which is immediately plant-available, in contrast to the organic-bound nitrogen in compost that mineralises slowly over months. Pathogen counts also drop sharply during digestion at 37°C (mesophilic) or 55°C (thermophilic), enabling FCO-compliant sale as Fermented Organic Manure.
Downstream handling defines the commercial value. Raw digestate is typically separated by screw press or centrifuge into a liquid fraction (5–8% DM, suitable for fertigation within 25 km) and a solid fraction (25–30% DM, transportable to 100 km or further processable into compost or pellets). Without separation, raw digestate is a logistical liability — 95% water, hard to spread evenly, and emits ammonia rapidly if surface-applied. With proper separation, drying, and pelletisation, the same digestate becomes a ₹6,000–10,000 per tonne FCO-registered Fermented Organic Manure product that can contribute 15–25% of total CBG plant revenue.
- Output of anaerobic digestion — nutrient-rich slurry at 90–95% moisture, pH 7–8.
- Composition: 1.5–4% N, 0.5–1.5% P, 1–3% K on dry basis; ammoniacal N is plant-available.
- Separation into liquid (fertigation) and solid (compost/pellet) fractions unlocks commercial value.
- Can contribute 15–25% of total CBG plant revenue when sold under FCO 1985 as FOM.
Common questions about Anaerobic Digestate
Plain-English answers to what people most often ask.
What is digestate from a biogas plant?
What is the difference between liquid digestate and solid digestate?
Does digestate require regulatory approval to sell in India?
Want the full picture, not just the term?
Adhāra Viveka gives you structured clarity on capital-intensive recycling and renewable-energy sectors — before you commit money or engage vendors.