gCO2

gCO2 stands for gram of carbon dioxide, a unit of mass used to quantify emissions of CO2. One gCO2 equals the mass of carbon dioxide released or stored, and 1,000 g equal 1 kilogram. In emissions inventories and product footprints, gCO2 is commonly used to express the amount of CO2 emitted by a process or activity, such as energy use, transportation, or industrial production.

Unlike gCO2e (grams of CO2 equivalent), which aggregates other greenhouse gases by their global warming potential, gCO2 reports only CO2 itself. Thus, gCO2 provides a direct measure of CO2 emissions, while gCO2e provides a broader measure of climate impact across multiple gases. Both concepts are used in environmental accounting, but they convey different scopes of impact.

Applications include transportation fuel efficiency (grams CO2 per passenger-kilometer or per mile), consumer product footprints, corporate sustainability reporting, and life cycle assessment. Emissions can be estimated from activity data using emission factors or measured directly from fuel use, energy consumption, or process data.

Limitations: gCO2 does not capture non-CO2 greenhouse gases unless converted to CO2e, and it does not by itself reflect the relative warming impact of different gases. The accuracy of gCO2 estimates depends on data quality, chosen boundaries, and the representativeness of emission factors. Common sources of CO2 include fossil fuel combustion for electricity and heating, transportation, and industrial processes such as cement production.