- Assurance (limited vs. reasonable)
- Independent third-party verification of reported sustainability data. Limited assurance provides a negative conclusion (nothing came to the auditor's attention suggesting error); reasonable assurance provides a positive opinion closer to a financial audit. CSRD begins with limited assurance and is designed to move toward reasonable assurance.
- Double materiality
- The CSRD principle requiring companies to report both how sustainability issues affect the company's financial value (financial materiality) and how the company's operations affect the climate and society (impact materiality), regardless of whether that impact affects earnings.
- Energy Reuse Effectiveness (ERE/ERF)
- A metric that credits a data center for heat it exports to a productive external use, such as a district heating network. Unlike PUE, it rewards heat recovery, turning waste-heat reuse from an unmeasured practice into a reported number under regimes like the EU Energy Efficiency Directive.
- Green steel
- Steel produced with substantially lower emissions than conventional blast-furnace steel, either by melting recycled scrap in an electric arc furnace powered by clean electricity, or by hydrogen direct reduction, which replaces carbon-emitting coke with hydrogen so the reduction step emits water vapor rather than carbon dioxide.
- Life-cycle assessment (LCA)
- A method of accounting for a product's environmental impact across its entire existence, from raw material extraction through manufacturing, transport, operation, and end-of-life disposal or recovery. It underpins the Scope 3 and embodied-carbon figures required by CSRD and California's SB 253, and relies on Environmental Product Declarations for input data.
- Power Usage Effectiveness (PUE)
- The ratio of a facility's total energy use to the energy delivered to its IT equipment. A perfect score is 1.0; the excess above 1.0 is largely cooling and overhead. It is a core efficiency metric that data center regulations increasingly require operators to disclose.
- Scope 1, 2, and 3 emissions
- The Greenhouse Gas Protocol's classification: Scope 1 is direct emissions from owned or controlled sources (e.g., backup generators); Scope 2 is emissions from purchased electricity; Scope 3 is value-chain emissions, including materials, construction, and purchased hardware. For data centers, Scope 2 typically dominates operations and Scope 3 captures embodied carbon.
- Supplementary cementitious materials (SCMs)
- Substances such as fly ash, ground granulated blast-furnace slag, or calcined clays that replace a portion of carbon-intensive clinker in concrete while providing similar binding performance. They are the dominant lever for producing low-carbon concrete, since most of cement's emissions come from clinker production.