Carbon footprint

The carbon footprint estimates the quantity of greenhouse gases emitted to satisfy the consumption of goods, services and infrastructure, wherever production takes place.

It is expressed in CO2 equivalent, a unit that converts each gas according to its global warming potential relative to carbon dioxide.

For digital technology

Manufacturing dominates. Extracting materials, producing semiconductors and assembling devices account for most emissions across the life of a device, well ahead of the electricity it consumes in operation.

The consequence is direct and frequently ignored: keeping a laptop for six years rather than three roughly halves its annual footprint, an effect no improvement in energy efficiency can match.

For an organisation, this places most emissions in scope 3, the indirect emissions of the value chain, which is also the hardest scope to measure.

Methods

• the GHG Protocol provides the international accounting method, structured in three scopes ;
• ISO 14064 makes the resulting declaration auditable by a third party ;
• Bilan Carbone provides an operational approach, widely used in France ;
• Life cycle assessment extends the analysis to impacts other than carbon.

These frameworks are compatible and produce comparable results. The difficulty lies not in choosing between them but in obtaining reliable data on manufacturing.

Limits

Carbon is one indicator among several. It says nothing about water, materials, land use or biodiversity, which for digital equipment are often more discriminating. An assessment reduced to carbon can validate a choice that is poor on every other criterion.

See also

• GHG Protocol · ISO 14064 · Bilan Carbone · Life cycle assessment · Manufacturing · Sustainable IT