1.5–15 g/kg (fresh basis) (nitrogen content fresh basis)
Also known as: digestate nitrogen range
The typical nitrogen concentration in fresh digestate — 1.5 to 15 grams of total nitrogen per kilogram of wet material, depending on feedstock and process.
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What is 1.5–15 g/kg (fresh basis)?
1.5–15 g/kg (fresh basis) is the total nitrogen concentration range in fresh, unseparated Indian biogas digestate, expressed as grams of N per kilogram of as-received wet material. The 10× spread reflects the diversity of feedstocks and process configurations. Low end (1.5–3 g/kg) is typical of dilute cattle-dung digesters with high-water feedstocks; high end (10–15 g/kg) corresponds to high-protein, low-moisture inputs like chicken litter, slaughterhouse waste, or distillery spent wash.
The fresh-basis convention is critical because tanker loading, application rates, and FCO 1985 product labels all use fresh weight. A digestate quoted at 2.5% N on dry basis sounds impressive, but if the material is 8% DM, the fresh-weight nitrogen is only 2 g/kg — meaning a 10 m³ tanker carries 20 kg of plant-available N, equivalent to about 45 kg of urea. Application rates of 30–50 cubic metres per hectare (60,000–100,000 litres per acre split into 2–3 doses) are normal for liquid digestate to deliver 60–100 kg N/ha across a crop cycle.
Within the 1.5–15 g/kg range, ammoniacal nitrogen (NH₄-N) typically represents 55–75%, with the balance as organic-bound nitrogen that mineralises over weeks. This split matters because ammoniacal N is immediately taken up by crops while organic N delivers residual fertility into the following season. Indian farmers familiar with split-dose urea application benefit from this dual-release profile if educated on it. Quality control for FCO 1985 sale requires lab measurement of both fractions on every batch, with reported uncertainty of ±15–20% being typical even at accredited labs. CBG plants targeting consistent N output therefore standardise feedstock blends and digester loading rather than relying on post-hoc lab adjustment.
- Total N range in fresh digestate spans 10×, driven by feedstock and moisture variability.
- Always convert dry-basis lab values to fresh-basis before sizing tankers and application rates.
- Ammoniacal N (immediately available) is 55–75% of total; organic N mineralises over weeks.
- Lab measurement uncertainty of ±15–20% is typical; consistent feedstock blends matter more than post-hoc adjustment.
Common questions about 1.5–15 g/kg (fresh basis)
Plain-English answers to what people most often ask.
What is the difference between fresh basis and dry matter basis for nitrogen?
How do I choose the right application rate for 8 g/kg nitrogen digestate?
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