Follow nitrogen through both separated fractions https://ramiran.eu/research/digestate-after-biogas/ A concentration alone cannot tell you where most nutrients went. Multiply each fraction’s mass by its concentration on the same basis, then compare the quantities with the input. Separation studies report different distributions; do not copy one plant’s percentage into another plant’s plan. A balance you can check by hand Consider a hypothetical 100-tonne fresh digestate batch containing 4 kg of total nitrogen per fresh tonne: 400 kg N enters separation. The measured outputs in this exercise are 80 fresh tonnes of liquid at 4.5 kg N/t and 20 fresh tonnes of solids at 2 kg N/t. StreamFresh massTotal N concentrationTotal N quantity Input100 t4 kg/t400 kg Liquid80 t4.5 kg/t360 kg Solid20 t2 kg/t40 kg Mass closes at 80 + 20 = 100 t. Nitrogen closes at 360 + 40 = 400 kg. The liquid carries 90% of the nitrogen in this invented example. That is an arithmetic result, not a general separation efficiency or a crop-available nitrogen estimate. What to do when a balance does not close Check whether all samples describe the same batch and time window. Check fresh/dry basis, kg/t versus g/kg, and total N versus ammonium N. Do not add different analytes. List unmeasured streams, additions, remaining tank contents and sampling or weighing uncertainty. Keep the residual as an unexplained quantity until evidence supports a cause. Do not label it an emission by subtraction alone. Each output still needs a storage, transport and compliant use route. A closed classroom balance does not establish field suitability, contaminant safety or the application rate. The cited primary study examines fractionation across full-scale plants; the numbers above are independently chosen teaching inputs. Text equivalent: 400 kg N in → 360 kg liquid → 40 kg solid → 400 = 360 + 40 Batch and period: __________________________ Input fresh mass: __________________________ Input total N concentration: __________________________ Liquid fresh mass and total N: __________________________ Solid fresh mass and total N: __________________________ Other streams/additions: __________________________ Mass residual: __________________________ Nitrogen residual: __________________________ Basis/analyte checks: __________________________ Unknowns and responsible reviewer: __________________________ Original nitrogen-flow drawing. Widths represent the fictional 90/10 split; fresh mass and total N remain distinct. https://doi.org/10.1016/j.biortech.2017.07.130