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🧪 Methodology

The PEGA Emissions Inventory combines two major international guidelines with a custom normalization layer provided by the pega R package.

📚 Reference Guidelines

  1. EMEP/EEA Air Pollutant Emission Inventory Guidebook: Used primarily for non-greenhouse gas pollutants (NOx, SOx, PM, VOCs, NH3, CO).
  2. IPCC Guidelines for National Greenhouse Gas Inventories: Used for GHGs (CO2, CH4, N2O).

🧮 Calculation Tiers

The project supports three tiers of estimation:

  • Tier 1: Simple method using default emission factors and national activity statistics.
  • Tier 2: Uses technology-specific emission factors (e.g., specific to the type of boiler or abatement technology).
  • Tier 3: Detailed models based on plant-level data, continuous monitoring, or complex process simulations.

📏 Unit Normalization

One of the most critical aspects of this project is the pre-normalization of emission factors.

In many inventories, units vary wildly (g/kg, kg/tonne, lb/MMBtu). In this project:

  • All energy-related factors are normalized to g/GJ (grams per Gigajoule).
  • Activity data must be converted to GJ before multiplication.
  • Resulting emissions are usually output in g or kg, which are then aggregated to Mg (Megagrams/Tonnes).

🧬 The pega Package Role

The pega package provides:

  • A curated database of EMEP/IPCC factors.
  • Functions to retrieve these factors based on standardized codes.
  • Utility functions for unit conversion and spatial mapping.

Example Retrieval

library(pega)
# Retrieve Tier 1 factors for Natural Gas in the Energy sector
factors <- ef(returnfdb = TRUE)[code == "1.A.1.a" & fuel == "Natural Gas" & type == "Tier 1 Emission Factor"]

❄️ Chemical Speciation

For post-processing, VOC and PM emissions are further speciated into chemical mechanisms (e.g., SAPRC-99, MOZART, CB6) to be used in atmospheric models. This logic is handled in the post/ directory.