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WST-INT

Waste Intensity Calculator

1. Identity

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Depends on module:

Purpose
Computes waste intensity by normalizing waste generated (total, hazardous, or non-hazardous) against an activity denominator (typically revenue), producing disclosure-ready intensity series aligned with ESRS E5 reporting patterns.

This engine is the Waste analogue of:

• MEID_CALC_ENERGY_INT
• MEID_CALC_WATER_INT
• MEID_CALC_GHG_INT

Typical usage

• Total waste generated per € revenue (t/€m)
• Hazardous waste per € revenue
• Non-hazardous waste per € revenue
• Inputs to benchmarking and trend analytics

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2. Contract References (ZAR)

2.1 Input Schema

ZAR Address: schema.compute.waste.intensity.inputs.v1_0_0

Required conceptual fields:

• waste: scalar or time-series (absolute waste quantity)
• denominator: scalar or time-series (e.g., revenue in EURm, production volume)
• intensity_basis: TOTAL | HAZARDOUS | NON_HAZARDOUS (default TOTAL)
• alignment: BY_YEAR | BY_INDEX (default BY_YEAR)

Optional:

• unit_waste: default tonne
• unit_denominator: e.g. EURm
• waste_by_category: optional map category → series (for future extensions)

Note: v1 focuses on a single intensity output per request. Per-category intensity can be introduced later without changing the core formula.

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2.2 Options Schema

ZAR Address: schema.compute.waste.intensity.options.v1_0_0

Common options:

• denominator_floor: default 1e-9
• missing_policy: ERROR | SKIP
• rounding: optional digits
• output_unit_style: t_per_EURm | t_per_EUR | auto (default auto)
• non_positive_denominator_policy: ERROR | FLOOR_AT_EPS (default ERROR)

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2.3 Output Schema

ZAR Address: schema.compute.waste.intensity.output.v1_0_0

Outputs include:

• waste_intensity
• metadata (basis, floors applied, alignment info, units)

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3. Accepted Input Shapes

A. Total waste intensity (scalar)

{
  "waste": 1285,
  "denominator": 250,
  "intensity_basis": "TOTAL"
}

B. Hazardous waste intensity (time-series)

{
  "waste": [[2025, 85], [2026, 82]],
  "denominator": [[2025, 250], [2026, 260]],
  "intensity_basis": "HAZARDOUS",
  "alignment": "BY_YEAR"
}

C. Total + hazard split resolved upstream

{
  "waste": {
    "total": [[2025, 1285]],
    "hazardous": [[2025, 85]],
    "non_hazardous": [[2025, 1200]]
  },
  "denominator": [[2025, 250]],
  "intensity_basis": "NON_HAZARDOUS"
}

All supported shapes MUST be normalized internally to:

Map<period, waste_value> + Map<period, denominator_value>

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4. Compute Semantics (Normative)

For each aligned period $t$:

4.1. Select waste basis

Let $W(t)$ be the selected waste series corresponding to intensity_basis:

• TOTAL: $W(t) = W_{\mathrm{generated,total}}(t)$
• HAZARDOUS: $W(t) = W_{\mathrm{generated,hazardous}}(t)$
• NON_HAZARDOUS: $W(t) = W_{\mathrm{generated,non-hazardous}}(t)$

If the caller supplies a raw waste series, it is treated as $W(t)$ directly; the basis label is still required for metadata.

4.2. Intensity formula

Let $D(t)$ be the denominator series (e.g. revenue).

$I(t) = \frac{W(t)}{\max(|D(t)|, \epsilon)}$

Where $\epsilon$ is denominator_floor.

4.3. Denominator policy

If non_positive_denominator_policy = ERROR, then:

• if $D(t) \le 0$, the computation MUST fail for that period (or entire run, depending on schema strictness).

If FLOOR_AT_EPS, then: $D(t) \leftarrow \max(D(t), \epsilon)$ and the event MUST be recorded in metadata.

4.4. Output units

If waste is tonne and denominator is EURm, then:

• $I(t)$ unit is tonne/EURm

The engine MUST propagate unit metadata to output:

• unit_waste
• unit_denominator
• derived unit_intensity

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5. Alignment Rules

BY_YEAR

• Waste and denominator must share period keys unless missing_policy = SKIP.

BY_INDEX

• Ordered alignment; length mismatch handled per missing_policy.

Metadata MUST include:

• aligned_periods
• missing_in_waste
• missing_in_denominator
• denominator_floor_applied_count
• non_positive_denominator_events (if any)

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6. Validation & Error Model

Invariants

• Values must be finite
• denominator_floor > 0
• Denominator must be positive under default policy
• intensity_basis must be valid

Error codes (suggested)

• WASTE_INT_MISSING_DENOMINATOR
• WASTE_INT_INVALID_BASIS
• WASTE_INT_ALIGNMENT_MISMATCH
• WASTE_INT_NON_POSITIVE_DENOMINATOR
• WASTE_INT_DENOMINATOR_ZERO_GUARDED (informational if floor applied)
• WASTE_INT_NON_FINITE_VALUE

Errors MUST include:

• engine cmi_short_code
• basis and period context

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7. Dependencies

MEID_CALC_WASTE_INT depends on:

• upstream waste totals (often from MEID_CALC_WASTE_AGGR)
• schema resolver (ZAR)

Declared via ZAR dependencies.

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8. Federation & Audit Requirements

To reproduce waste intensity externally, the export MUST include:

• engine identity (cmi or zar_code)
• engine build proof (execution_ref + build_hash)
• input/options/output schemas used
• waste series selected (total/hazardous/non-hazardous)
• denominator series (e.g. revenue)
• denominator floor and denominator-policy settings

Provenance chain MUST show:

… → MEID_CALC_WASTE_INT → …

with cmi_short_code recorded in USO tail arrays.

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9. Performance Notes

• Complexity: $O(n)$ over periods
• Memory: $O(n)$
• Suitable for batch reporting and KPI analytics

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10. Methods Served (v1)

• Waste.generated.intensity
• Waste.hazardous.intensity
• Waste.non_hazardous.intensity

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