CO2 Carbon Footprint Calculator

Business Case

Problem Statement

Sustainability requirements demand carbon tracking:

• Need to quantify embodied carbon
• Material selection impact unclear
• Reporting requirements increasing
• No integration with BIM workflow

Solution

Calculate CO2 emissions from BIM quantities using EPD (Environmental Product Declaration) data and carbon coefficients.

Business Value

• Sustainability - Meet green building requirements
• Design optimization - Identify high-carbon elements
• Reporting - Automated carbon reports
• Decision support - Compare material alternatives

Technical Implementation

import pandas as pd
from datetime import datetime
from typing import Dict, Any, List, Optional, Tuple
from dataclasses import dataclass, field
from enum import Enum


class LifeCycleStage(Enum):
    """EN 15978 Life Cycle Stages."""
    A1_A3 = "a1_a3"  # Product stage
    A4 = "a4"        # Transport to site
    A5 = "a5"        # Construction
    B1_B7 = "b1_b7"  # Use stage
    C1_C4 = "c1_c4"  # End of life
    D = "d"          # Beyond system boundary


class MaterialCategory(Enum):
    """Material categories for carbon calculation."""
    CONCRETE = "concrete"
    STEEL = "steel"
    TIMBER = "timber"
    ALUMINUM = "aluminum"
    GLASS = "glass"
    BRICK = "brick"
    INSULATION = "insulation"
    GYPSUM = "gypsum"
    OTHER = "other"


@dataclass
class CarbonCoefficient:
    """Carbon emission coefficient for a material."""
    material: str
    category: MaterialCategory
    kgco2_per_unit: float  # kg CO2e per unit
    unit: str  # kg, m3, m2, etc.
    stage: LifeCycleStage
    source: str  # EPD reference
    uncertainty: float = 0.1  # 10% default uncertainty


@dataclass
class CarbonResult:
    """Carbon calculation result for an element."""
    element_id: str
    element_name: str
    material: str
    category: MaterialCategory
    quantity: float
    unit: str
    kgco2_per_unit: float
    total_kgco2: float
    stage: LifeCycleStage
    level: str = ""
    notes: str = ""


@dataclass
class CarbonSummary:
    """Carbon footprint summary."""
    total_kgco2: float
    total_tonco2: float
    by_material: Dict[str, float]
    by_category: Dict[str, float]
    by_stage: Dict[str, float]
    by_level: Dict[str, float]
    element_count: int
    gfa: float  # Gross Floor Area
    kgco2_per_m2: float


class CarbonCoefficientDatabase:
    """Database of carbon emission coefficients."""

    def __init__(self):
        self.coefficients: List[CarbonCoefficient] = []
        self._load_default_coefficients()

    def _load_default_coefficients(self):
        """Load standard carbon coefficients (EPD-based)."""
        # Concrete products
        self.add_coefficient(CarbonCoefficient(
            material="Concrete C30/37", category=MaterialCategory.CONCRETE,
            kgco2_per_unit=250, unit="m3", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Concrete"
        ))
        self.add_coefficient(CarbonCoefficient(
            material="Concrete C40/50", category=MaterialCategory.CONCRETE,
            kgco2_per_unit=300, unit="m3", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - High Strength Concrete"
        ))
        self.add_coefficient(CarbonCoefficient(
            material="Reinforcement Steel", category=MaterialCategory.STEEL,
            kgco2_per_unit=1.99, unit="kg", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Rebar"
        ))

        # Steel products
        self.add_coefficient(CarbonCoefficient(
            material="Structural Steel", category=MaterialCategory.STEEL,
            kgco2_per_unit=2.5, unit="kg", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Structural Steel"
        ))
        self.add_coefficient(CarbonCoefficient(
            material="Steel Sheet", category=MaterialCategory.STEEL,
            kgco2_per_unit=2.3, unit="kg", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Sheet Metal"
        ))

        # Timber products
        self.add_coefficient(CarbonCoefficient(
            material="Softwood Timber", category=MaterialCategory.TIMBER,
            kgco2_per_unit=-500, unit="m3", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - CLT (carbon sequestration)"
        ))
        self.add_coefficient(CarbonCoefficient(
            material="Glulam", category=MaterialCategory.TIMBER,
            kgco2_per_unit=-350, unit="m3", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Glued Laminated Timber"
        ))

        # Aluminum
        self.add_coefficient(CarbonCoefficient(
            material="Aluminum Profile", category=MaterialCategory.ALUMINUM,
            kgco2_per_unit=8.0, unit="kg", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Aluminum"
        ))

        # Glass
        self.add_coefficient(CarbonCoefficient(
            material="Float Glass", category=MaterialCategory.GLASS,
            kgco2_per_unit=15.0, unit="m2", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Float Glass"
        ))
        self.add_coefficient(CarbonCoefficient(
            material="Double Glazing Unit", category=MaterialCategory.GLASS,
            kgco2_per_unit=35.0, unit="m2", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - IGU"
        ))

        # Masonry
        self.add_coefficient(CarbonCoefficient(
            material="Clay Brick", category=MaterialCategory.BRICK,
            kgco2_per_unit=0.24, unit="kg", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Clay Brick"
        ))

        # Insulation
        self.add_coefficient(CarbonCoefficient(
            material="Mineral Wool", category=MaterialCategory.INSULATION,
            kgco2_per_unit=1.2, unit="kg", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Mineral Wool"
        ))
        self.add_coefficient(CarbonCoefficient(
            material="EPS Insulation", category=MaterialCategory.INSULATION,
            kgco2_per_unit=3.5, unit="kg", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - EPS"
        ))

        # Gypsum
        self.add_coefficient(CarbonCoefficient(
            material="Gypsum Board", category=MaterialCategory.GYPSUM,
            kgco2_per_unit=2.8, unit="m2", stage=LifeCycleStage.A1_A3,
            source="Generic EPD - Plasterboard"
        ))

    def add_coefficient(self, coefficient: CarbonCoefficient):
        """Add carbon coefficient to database."""
        self.coefficients.append(coefficient)

    def find_coefficient(self, material_name: str,
                        stage: LifeCycleStage = LifeCycleStage.A1_A3) -> Optional[CarbonCoefficient]:
        """Find matching coefficient for material."""
        material_lower = material_name.lower()

        # Direct match
        for coef in self.coefficients:
            if coef.material.lower() == material_lower and coef.stage == stage:
                return coef

        # Partial match
        for coef in self.coefficients:
            if material_lower in coef.material.lower() or coef.material.lower() in material_lower:
                if coef.stage == stage:
                    return coef

        # Category match
        category = self._guess_category(material_name)
        for coef in self.coefficients:
            if coef.category == category and coef.stage == stage:
                return coef

        return None

    def _guess_category(self, material_name: str) -> MaterialCategory:
        """Guess material category from name."""
        name_lower = material_name.lower()

        if any(w in name_lower for w in ['concrete', 'cement', 'mortar']):
            return MaterialCategory.CONCRETE
        if any(w in name_lower for w in ['steel', 'iron', 'metal']):
            return MaterialCategory.STEEL
        if any(w in name_lower for w in ['wood', 'timber', 'lumber', 'plywood', 'clt']):
            return MaterialCategory.TIMBER
        if any(w in name_lower for w in ['aluminum', 'aluminium']):
            return MaterialCategory.ALUMINUM
        if any(w in name_lower for w in ['glass', 'glazing']):
            return MaterialCategory.GLASS
        if any(w in name_lower for w in ['brick', 'masonry', 'block']):
            return MaterialCategory.BRICK
        if any(w in name_lower for w in ['insulation', 'wool', 'foam', 'eps', 'xps']):
            return MaterialCategory.INSULATION
        if any(w in name_lower for w in ['gypsum', 'drywall', 'plaster']):
            return MaterialCategory.GYPSUM

        return MaterialCategory.OTHER


class CO2FootprintCalculator:
    """Calculate carbon footprint from BIM data."""

    def __init__(self, coefficient_db: CarbonCoefficientDatabase = None):
        self.db = coefficient_db or CarbonCoefficientDatabase()
        self.results: List[CarbonResult] = []
        self.warnings: List[str] = []

    def calculate_element(self, element: Dict[str, Any],
                         stage: LifeCycleStage = LifeCycleStage.A1_A3) -> Optional[CarbonResult]:
        """Calculate carbon for single element."""
        material = element.get('material', '')
        if not material:
            self.warnings.append(f"Element {element.get('element_id')} has no material")
            return None

        coefficient = self.db.find_coefficient(material, stage)
        if not coefficient:
            self.warnings.append(f"No coefficient found for material: {material}")
            return None

        # Get quantity in correct unit
        quantity = self._get_quantity(element, coefficient.unit)
        if quantity is None or quantity <= 0:
            return None

        total_kgco2 = quantity * coefficient.kgco2_per_unit

        result = CarbonResult(
            element_id=str(element.get('element_id', '')),
            element_name=str(element.get('name', '')),
            material=material,
            category=coefficient.category,
            quantity=quantity,
            unit=coefficient.unit,
            kgco2_per_unit=coefficient.kgco2_per_unit,
            total_kgco2=total_kgco2,
            stage=stage,
            level=str(element.get('level', ''))
        )

        self.results.append(result)
        return result

    def _get_quantity(self, element: Dict[str, Any], unit: str) -> Optional[float]:
        """Get quantity in required unit."""
        unit_lower = unit.lower()

        if unit_lower == 'm3':
            return float(element.get('volume', 0) or 0)
        elif unit_lower == 'm2':
            return float(element.get('area', 0) or 0)
        elif unit_lower in ['kg', 'kilogram']:
            # Try weight, then estimate from volume
            weight = element.get('weight', 0)
            if weight:
                return float(weight)
            # Estimate from volume with density
            volume = element.get('volume', 0)
            if volume:
                density = self._estimate_density(element.get('material', ''))
                return float(volume) * density
        elif unit_lower in ['m', 'meter']:
            return float(element.get('length', 0) or 0)

        return None

    def _estimate_density(self, material: str) -> float:
        """Estimate material density in kg/m3."""
        material_lower = material.lower()

        densities = {
            'concrete': 2400,
            'steel': 7850,
            'timber': 500,
            'aluminum': 2700,
            'glass': 2500,
            'brick': 1800,
            'gypsum': 800
        }

        for key, density in densities.items():
            if key in material_lower:
                return density

        return 1500  # Default density

    def calculate_from_dataframe(self, df: pd.DataFrame,
                                 stage: LifeCycleStage = LifeCycleStage.A1_A3) -> List[CarbonResult]:
        """Calculate carbon for all elements in DataFrame."""
        self.results = []
        self.warnings = []

        for _, row in df.iterrows():
            self.calculate_element(row.to_dict(), stage)

        return self.results

    def get_summary(self, gfa: float = 0) -> CarbonSummary:
        """Generate carbon footprint summary."""
        by_material = {}
        by_category = {}
        by_stage = {}
        by_level = {}

        for result in self.results:
            # By material
            by_material[result.material] = by_material.get(result.material, 0) + result.total_kgco2

            # By category
            cat = result.category.value
            by_category[cat] = by_category.get(cat, 0) + result.total_kgco2

            # By stage
            stg = result.stage.value
            by_stage[stg] = by_stage.get(stg, 0) + result.total_kgco2

            # By level
            if result.level:
                by_level[result.level] = by_level.get(result.level, 0) + result.total_kgco2

        total_kgco2 = sum(r.total_kgco2 for r in self.results)

        return CarbonSummary(
            total_kgco2=round(total_kgco2, 2),
            total_tonco2=round(total_kgco2 / 1000, 2),
            by_material=by_material,
            by_category=by_category,
            by_stage=by_stage,
            by_level=by_level,
            element_count=len(self.results),
            gfa=gfa,
            kgco2_per_m2=round(total_kgco2 / gfa, 2) if gfa > 0 else 0
        )

    def export_results(self, output_path: str):
        """Export results to Excel."""
        with pd.ExcelWriter(output_path, engine='openpyxl') as writer:
            # Detailed results
            results_df = pd.DataFrame([{
                'Element ID': r.element_id,
                'Element Name': r.element_name,
                'Material': r.material,
                'Category': r.category.value,
                'Quantity': r.quantity,
                'Unit': r.unit,
                'kg CO2e/unit': r.kgco2_per_unit,
                'Total kg CO2e': round(r.total_kgco2, 2),
                'Level': r.level
            } for r in self.results])

            results_df.to_excel(writer, sheet_name='Details', index=False)

            # Summary
            summary = self.get_summary()
            summary_df = pd.DataFrame([
                {'Metric': 'Total kg CO2e', 'Value': summary.total_kgco2},
                {'Metric': 'Total ton CO2e', 'Value': summary.total_tonco2},
                {'Metric': 'Elements Analyzed', 'Value': summary.element_count}
            ])
            summary_df.to_excel(writer, sheet_name='Summary', index=False)

        return output_path

Quick Start

# Initialize calculator
calculator = CO2FootprintCalculator()

# Load BIM quantities
elements = pd.read_excel("bim_quantities.xlsx")

# Calculate carbon
results = calculator.calculate_from_dataframe(elements)

# Get summary
summary = calculator.get_summary(gfa=5000)  # 5000 m2 GFA
print(f"Total: {summary.total_tonco2} ton CO2e")
print(f"Per m2: {summary.kgco2_per_m2} kg CO2e/m2")

Common Use Cases

1. Material Comparison

# Compare concrete vs timber
concrete_elements = elements[elements['material'].str.contains('Concrete')]
timber_elements = elements[elements['material'].str.contains('Timber')]

2. Target Compliance

TARGET_KGCO2_M2 = 500  # LEED/BREEAM target
if summary.kgco2_per_m2 > TARGET_KGCO2_M2:
    print(f"Warning: Exceeds target by {summary.kgco2_per_m2 - TARGET_KGCO2_M2} kg/m2")

3. Export Report

calculator.export_results("carbon_report.xlsx")

Resources

• DDC Book: Chapter 3.3 - CO2 Estimation
• Reference: EN 15978, EPD databases