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Chapter 3


Some concepts to understand when dealing with Green IT.

Green IT, digital sustainability, responsible digital practice…
These terms are often used to differentiate the types of actions that make it possible to reduce IT’s environmental footprint. To keep this discussion simple, we will use them interchangeably to refer to all IT activity around sustainable development, such as reduction of energy consumption, electronic and electrical equipment waste, carbon footprint, etc.

Carbon neutral

This expression means that any CO2 emissions released into the atmosphere through an organisation’s activities are offset by the elimination of an equivalent amount. Carbon neutrality is usually achieved through a combination of actions:

  • Eliminating some of the emission sources along the value chain;
  • Permanently storing part of the emissions immediately after they are emitted (e.g. by injecting them into natural carbon sinks);
  • Offsetting the remaining emissions by investing in carbon-negative projects (e.g. reforestation).

Net zero

In this case, carbon-emitting activities are offset by other business lines that remove carbon from the atmosphere. The balance is established at a company level.

Carbon negative

Once net zero has been achieved, the organisation can set itself a goal to remove even more carbon than it emits, to highlight the company’s positive impact on the climate. In practice, this is rarely possible except in very specific circumstances.

Scope 1 / 2 / 3

The words Scope 1, Scope 2 and Scope 3 are generally used in the context of measuring a product or organisation’s greenhouse gas (GHG) emissions. These scopes refer to the ‘ownership’ categories for the emissions

  • Scope 1: direct emissions;
  • Scope 2: indirect emissions linked to energy consumption;
  • Scope 3: other indirect emissions produced upstream and downstream of the company’s operations (such as a supplier’s transport choices, employee commuting or waste management)


The PUE (Power Usage Effectiveness) measures the energy efficiency of a data centre. The lower the PUE, the lower the energy consumption.