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Compost Feedstock C:N Record Check

Reconcile two dry-feedstock carbon and nitrogen analyses with a laboratory-reported compost blend C:N ratio without assigning a universal recipe grade.

Use this result well

Inputs that matter
Two documented feedstock dry masses, matching dry-basis carbon and nitrogen analyses, and a laboratory blend C:N ratio
Output to expect
Calculated blend carbon and nitrogen mass, calculated C:N and signed laboratory-ratio difference
How it works
Reconciles one two-feedstock dry-basis batch record; it does not label a universal ideal recipe or certify the composting process
  • Match batch, representative sampling, dry-matter conversion, laboratory methods and timing; feedstock C and N vary and a ratio-only ingredient record is insufficient.
  • Manage moisture, porosity/aeration, temperature, pH, degradability, turning, odors, pathogens, safety and intended end use under the current site plan and qualified guidance.

Choose your path

Built around the job you need to finish

Reconcile two documented dry-feedstock carbon and nitrogen analyses with a laboratory-reported C:N ratio for the same compost blend.

Compost operator checking a batch worksheet

Reproduce carbon mass, nitrogen mass and blend C:N from actual dry-basis analyses.

Enter both feedstock dry masses, matching lab C and N percentages, and the same-batch blend ratio.

Sees the signed laboratory difference without receiving a generic ideal grade.

Laboratory reviewer checking representativeness

Keep sampling, method, moisture conversion and batch identity attached.

Confirm the analyses and blend sample share compatible dry-matter and laboratory bases before comparing them.

Does not reconcile unlike samples or wet- and dry-basis values.

Facility manager managing process risk

Avoid treating C:N arithmetic as proof the pile will compost safely or meet end-use rules.

Review moisture, porosity/aeration, temperature, pH, turning, odors, pathogens and end-use records separately.

Uses the result as one recipe record, not process approval.

Authoritative checks for this tool

Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.

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Reference & details

How it works

Dry-basis component masses

For each documented feedstock, multiply entered dry mass by its matching dry-basis carbon percentage and nitrogen percentage. Add the two carbon masses and the two nitrogen masses without inferring either element from C:N alone.

Blend ratio and reconciliation

Divide calculated total carbon mass by calculated total nitrogen mass, then subtract the entered laboratory blend C:N ratio. The result reports the absolute difference and whether the calculation is above or below the laboratory record.

Scope and process controls

The arithmetic covers one two-feedstock dry-basis record. NRCS guidance also requires representative sampling and management of moisture, porosity, aeration, temperature, pH, turning, odors, pathogens and intended end use.

Updated: August 2026

Example Scenarios

An operator checks whether documented feedstock analyses reproduce the laboratory C:N result for the mixed batch.

A reviewer confirms that mass, carbon, nitrogen, moisture conversion, sampling date and batch identity share a compatible basis.

A facility retains the calculation as one recipe record while separately monitoring the biological process and end-use requirements.

Common Mistakes to Avoid

Using wet mass with dry-basis carbon and nitrogen percentages

Convert representative feedstock quantities to dry mass using documented moisture results before applying dry-basis laboratory percentages.

Calling the calculated C:N ratio an ideal compost recipe

Treat it as one batch record. Moisture, carbon availability, porosity, aeration, temperature, pH, turning, safety and end use still control interpretation.

FAQ

A ratio alone does not reveal the mass fraction of either element. Matched dry-basis carbon and nitrogen analyses support a reproducible component mass balance.

No. NRCS describes C:N as one planning factor alongside moisture, porosity, aeration, temperature, degradability and other process and end-use controls.

Only after confirming representative sampling, batch identity, dry-matter basis and compatible methods. Otherwise the numeric difference may reflect the records rather than the mix.

The C:N calculated from the entered feedstock analyses is lower than the entered laboratory blend ratio by the displayed ratio points. It is not automatically a process failure.

Keep feedstock and batch IDs, sampling date/location, wet and dry masses, moisture conversion, C/N laboratory methods, blend sampling, process observations and intended end use.

About Compost Feedstock C:N Record Check

This worksheet reconciles measured dry-feedstock carbon and nitrogen records with a laboratory blend C:N result. It deliberately avoids reconstructing carbon from a ratio or issuing a universal Ideal status.