Closing the mass balance: lessons from year-end 2024
Eight million kilograms in, two and a half million out, and a 0.5% tolerance to defend.
title: "Closing the mass balance: lessons from year-end 2024" date: "2026-04-12" excerpt: "Eight million kilograms in, two and a half million out, and a 0.5% tolerance to defend."
The first time we ran a year-end mass balance against the Girardot data, we were not closing the books — we were finding out which Excel formulas had been quietly wrong for nine months.
This is the story of replacing them.
What the numbers had to do
Eight million kilograms of mixed plastic entered the plant in 2024. Of those, roughly two and a half million left as OUTPUT EU certified biofuel — the fraction that survived intake QC, processing, the C14 sample, the certifier review and the POS issuance.
Everything in between — PLUS PROD, EU PROD, carbon black, metal scrap, water, syngas, losses — had to add up to within 0.5% of input. That is the closure tolerance ISCC EU expects you to defend in front of an auditor.
The actual hard part
The hard part is not arithmetic. The hard part is that the closure has to remain true after a load is recategorised three months later because the certifier flagged a C14 anomaly. Spreadsheets do not survive that. An append-only ledger does.
The auditor opened a tablet, queried any month of 2024, and the numbers reconciled in seconds. That conversation used to take days.
What the schema needs to know
- Which load came from which supplier on which truck on which day.
- Which production batch consumed which loads.
- Which sample was drawn from which batch and which lab certified it.
- Which POS document attests which kilogram of output.
Lose any one of those edges and the closure becomes a story instead of a fact.