Carbon Accounting
What the exam expects
Carbon accounting follows the GHG Protocol: Scope 1 direct emissions, Scope 2 purchased electricity/steam, and Scope 3 value-chain emissions. Know organizational and operational boundaries, consolidation approaches, emission factors, CO2e, and global warming potential versions. Scope 2 has location-based and market-based reporting; renewable energy contracts and certificates affect the market-based result. Scope 3 includes purchased goods, business travel, commuting, waste, and use of sold products. Offsets are not reductions inside the inventory boundary. Refrigerant leaks are Scope 1 and can be significant.
Traps
Mixing Scope 1 and Scope 3, ignoring the dual Scope 2 report, or treating offsets as zero-emission energy are common errors. Watch units: kg versus tonnes, therms versus MMBtu, and gross versus net calorific value. Emission factors must match the geography, year, and activity data.
Worked example
Electricity is 1,000,000 kWh at 0.40 kg CO2e/kWh = 400,000 kg = 400 tCO2e. Natural gas is 10,000 therms at 5.3 kg CO2e/therm = 53,000 kg = 53 tCO2e. Total Scope 1 plus Scope 2 location-based emissions are 453 tCO2e before any market-based adjustment.