Which statement best describes carbon intensity in energy systems?

• A. Carbon intensity is the total energy produced by a plant
• B. Carbon intensity measures the amount of CO2 emitted per unit of energy produced
• C. Carbon intensity is the energy efficiency of a process
• D. Carbon intensity is the energy stored per unit CO2 emitted

Answer: (B)

Carbon intensity is a measure of how much CO2 is released for each unit of energy produced. It helps compare how clean different energy sources or power systems are, usually expressed as kilograms of CO2 per kilowatt-hour (kg CO2/kWh) or per unit of energy. A lower carbon intensity means less CO2 emitted per unit of energy, which is desirable for reducing emissions in electricity generation and overall energy use. The value depends on the fuel and technology: coal-fired plants typically have higher carbon intensity than natural gas plants, and renewable sources have very low or near-zero carbon intensity. This concept is distinct from total energy production (quantity of energy produced), energy efficiency (how effectively energy is converted to useful work), and energy stored per unit CO2 emitted (not a standard metric in energy systems).