carbon-accounting-ghg-protocol

Carbon Accounting & GHG Protocol Skill Guide

This skill governs mathematical modeling, emission factor ingestion, and audit trail generation for enterprise carbon accounting engines compliant with the GHG Protocol.

1. Greenhouse Gas Scope Architecture

The GHG Protocol categorizes greenhouse gas emissions into three operational scopes:

[ Global Corporate Boundary ]
  |
  |-- SCOPE 1 (Direct Emissions)
  |   |-- Stationary combustion (boilers, natural gas)
  |   +-- Mobile fleet combustion (gasoline/diesel company vehicles)
  |
  |-- SCOPE 2 (Indirect Energy Emissions)
  |   |-- Location-based: Regional grid average factor (eGRID / IEA)
  |   +-- Market-based: Supplier-specific contracts / Renewable Energy Certificates (RECs)
  |
  +-- SCOPE 3 (Value Chain Indirect)
      |-- Category 1: Purchased Goods and Services
      |-- Category 6: Business Travel (flights, hotels)
      +-- Category 7: Employee Commuting & Remote Work

2. Production Code Implementation (Python)

A. Carbon Footprint Calculation Engine

from decimal import Decimal
from typing import Literal
from pydantic import BaseModel


class EmissionFactor(BaseModel):
    activity_unit: str  # e.g. "kWh", "liter_diesel", "passenger_km"
    co2e_factor_kg: Decimal  # kg CO2e per activity unit
    source: str  # e.g. "EPA 2024", "DEFRA 2023"


class ActivityRecord(BaseModel):
    id: str
    facility_id: str
    scope: Literal["SCOPE_1", "SCOPE_2", "SCOPE_3"]
    activity_type: str
    quantity: Decimal
    unit: str


class CarbonLedgerEngine:
    def __init__(self, factors: dict[str, EmissionFactor]):
        self.factors = factors

    def calculate_emission_kg(self, record: ActivityRecord) -> Decimal:
        factor_key = f"{record.activity_type}_{record.unit}"
        factor = self.factors.get(factor_key)

        if not factor:
            raise ValueError(f"No emission factor found for {factor_key}")

        # Total kg CO2e = Activity Quantity * Emission Factor
        co2e_kg = record.quantity * factor.co2e_factor_kg
        return co2e_kg

    def compute_facility_summary(self, records: list[ActivityRecord]) -> dict:
        summary = {
            "scope_1_mt": Decimal("0.0"),
            "scope_2_mt": Decimal("0.0"),
            "scope_3_mt": Decimal("0.0"),
            "total_co2e_metric_tonnes": Decimal("0.0"),
        }

        for r in records:
            kg = self.calculate_emission_kg(r)
            metric_tonnes = kg / Decimal("1000.0")

            if r.scope == "SCOPE_1":
                summary["scope_1_mt"] += metric_tonnes
            elif r.scope == "SCOPE_2":
                summary["scope_2_mt"] += metric_tonnes
            elif r.scope == "SCOPE_3":
                summary["scope_3_mt"] += metric_tonnes

        summary["total_co2e_metric_tonnes"] = (
            summary["scope_1_mt"] + summary["scope_2_mt"] + summary["scope_3_mt"]
        )
        return summary