Carbon Methodology

Overview

CarbonTrail estimates the carbon footprint of e-commerce shipments using a transparent, conservative methodology. This document explains our approach, assumptions, and limitations.

Our goal is to provide consistent, comparable estimates that help merchants understand and reduce their shipping-related emissions—not to replace comprehensive lifecycle assessments.

What We Calculate

CarbonTrail estimates Scope 3 downstream transportation emissions for shipped orders. This includes:

• CO₂ equivalent emissions from freight transport
• Distance-based calculations using origin and destination
• Weight-based emission factors

What We Do NOT Calculate

• Scope 1 or Scope 2 emissions
• Product manufacturing emissions
• Packaging production emissions
• Last-mile delivery specifics
• Return shipment emissions (tracked separately)
• Warehouse operations

Calculation Formula

kgCO₂e = distance_km × weight_kg × emission_factor

Distance Calculation

• Uses Haversine formula for great-circle distance
• Origin: Merchant-configured warehouse location
• Destination: Order shipping address (postcode-level)
• Coordinates derived from postcode centroids

Weight Determination

We determine weight using the following priority order:

• Shopify line item weights (if available)
• Product weight cache
• Merchant default weight
• Global fallback: 500g

Emission Factors

Transport Mode Inference

• Same country → Ground
• Adjacent countries (land border) → Ground
• International + >3000km → Air
• Default international → Air

Assumptions & Limitations

We Assume

• Direct routing (no hub-and-spoke modeling)
• Average vehicle efficiency for mode
• Full container/truck utilization rates
• Standard freight conditions

We Do NOT Assume

• Specific carrier efficiency
• Actual routing taken
• Real-time traffic or weather
• Multi-modal transport splits

Accuracy Statement

Our estimates are designed for consistency and comparability across orders and time periods. They should not be used for regulatory compliance without independent verification.

What We Explicitly Do NOT Claim

• Certification of carbon neutrality
• Regulatory compliance verification
• Lifecycle assessment completeness
• Scope 1/2 coverage
• Supply chain emissions coverage

Offset Integrity

When offsets are purchased through CarbonTrail:

• Offsets are sourced from verified providers (Patch, Cloverly)
• Each transaction includes provider reference ID
• Project details are recorded for audit
• We do not claim "carbon neutral" status for merchants

Versioning & Updates

All calculations are tagged with a version number. When methodology changes:

• New version number assigned
• Historical calculations retain original version
• Merchants notified of material changes
• Recalculation available on request

Data Retention

• Order emissions data: Retained indefinitely
• Calculation inputs: Stored with each order
• Offset transactions: Permanent audit trail
• Methodology version: Tagged per calculation