Definition: IT Sustainability as an Architectural Discipline

What is IT Sustainability?

IT Sustainability is the discipline of designing, operating and continuously improving information systems so that their energy consumption, resource usage and greenhouse gas emissions are measurably minimized — without compromising functionality, availability or security.

IT Sustainability encompasses three levels:

Level	Focus	Examples
Infrastructure Efficiency	Physical and virtualized resources	ARM/Graviton instances, green regions, idle elimination, storage lifecycle
Software Efficiency	Algorithms, architecture patterns, data flows	Event-driven instead of polling, caching, SCI measurement, lean dependencies
Governance & Reporting	Measurement, reporting, regulatory compliance	CSRD reporting obligation, GHG Protocol Scope 3, SBTi targets, ESG data automation

Level

Focus

Examples

Infrastructure Efficiency

Physical and virtualized resources

ARM/Graviton instances, green regions, idle elimination, storage lifecycle

Software Efficiency

Algorithms, architecture patterns, data flows

Event-driven instead of polling, caching, SCI measurement, lean dependencies

Governance & Reporting

Measurement, reporting, regulatory compliance

CSRD reporting obligation, GHG Protocol Scope 3, SBTi targets, ESG data automation

The Sustainability Maturity Spectrum

The sustainability maturity of an IT organization can be described in five stages:

Stage	Name	Characteristics
1	Blind	No measurement, no accountability. Emissions unknown. IT not in ESG reports.
2	Visible	Cloud provider tools activated. Emissions are occasionally reviewed. No targets.
3	Reported	Structured measurement, workload attribution. Data flows into ESG/CSRD reports. Baseline defined.
4	Optimized	Active reduction measures: Graviton, idle elimination, lifecycle policies. Goals measurably tracked.
5	Carbon-Neutral/Positive	Emission reduction at SBTi target level. Remaining emissions offset through verified compensation or avoided entirely.

Stage

Name

Characteristics

Blind

No measurement, no accountability. Emissions unknown. IT not in ESG reports.

Visible

Cloud provider tools activated. Emissions are occasionally reviewed. No targets.

Reported

Structured measurement, workload attribution. Data flows into ESG/CSRD reports. Baseline defined.

Optimized

Active reduction measures: Graviton, idle elimination, lifecycle policies. Goals measurably tracked.

Carbon-Neutral/Positive

Emission reduction at SBTi target level. Remaining emissions offset through verified compensation or avoided entirely.

Stage 1 (Blind) is no longer an acceptable position for organizations subject to CSRD. CSRD requires disclosure of material environmental information — ignorance is not a defense.

GHG Protocol: Scope 1, 2, 3 in the IT Context

The Greenhouse Gas (GHG) Protocol is the international standard for measuring and reporting greenhouse gas emissions. It defines three emission classes:

Scope 1 – Direct Emissions

Own combustion processes and vehicles. Marginal for most cloud-first organizations (on-premise server rooms with their own diesel generators are Scope 1).

IT relevance: Low for pure cloud operations; relevant for hybrid scenarios with own data centers.

Scope 2 – Purchased Energy (Indirect Emissions)

Emissions from the generation of purchased electricity, heat or steam.

IT relevance: Cloud provider energy is Scope 2 — but cloud providers purchase this energy as a service and pass it on. For customers, cloud energy is typically recorded as Scope 3.

Method	Description
Location-based	Emission factor of the regional electricity grid (gCO₂eq/kWh). Reflects actual local mix.
Market-based	Emission factor of actually purchased electricity (certificates of origin, PPAs, RECs). Allows "zero emissions" through certificates — controversial in terms of verification strength.

Method

Description

Location-based

Emission factor of the regional electricity grid (gCO₂eq/kWh). Reflects actual local mix.

Market-based

Emission factor of actually purchased electricity (certificates of origin, PPAs, RECs). Allows "zero emissions" through certificates — controversial in terms of verification strength.

Scope 3 – Indirect Emissions in the Value Chain

All other indirect emissions — upstream and downstream.

IT relevance: Cloud IT is Scope 3 of the customer organization:

Category 11: Use of sold products / purchased services → cloud compute, storage, SaaS
Category 1: Purchased goods/services → hardware, software licenses

Scope 3 is the hardest segment to measure and reduce — and at the same time the one that offers the greatest leverage for cloud companies. AWS, Azure and GCP have developed tools for Scope 3 attribution to their customers: AWS Customer Carbon Footprint Tool, Azure Emissions Impact Dashboard, GCP Carbon Footprint.

Software Carbon Intensity (SCI)

The Software Carbon Intensity (SCI) is a standard developed by the Green Software Foundation for measuring the carbon intensity of software:

SCI = ((E × I) + M) / R

Variable Name Description

Variable	Name	Description
`E`	Energy (kWh)	Energy consumed by the system for one functional unit
`I`	Carbon Intensity (gCO₂eq/kWh)	Intensity of the electricity grid at the execution location (location-based or market-based)
`M`	Embodied Emissions (gCO₂eq)	Proportional emissions from hardware manufacturing and disposal
`R`	Functional Unit	Reference unit: one API request, one transaction, one hour, one user

E

Energy (kWh)

Energy consumed by the system for one functional unit

I

Carbon Intensity (gCO₂eq/kWh)

Intensity of the electricity grid at the execution location (location-based or market-based)

M

Embodied Emissions (gCO₂eq)

Proportional emissions from hardware manufacturing and disposal

R

Functional Unit

Reference unit: one API request, one transaction, one hour, one user

Example: An API processes 1,000 requests/hour and consumes 0.5 kWh. With an emission factor of 200 gCO₂eq/kWh (e.g. region us-east-1) and negligible M:

SCI = (0.5 kWh × 200 gCO₂eq/kWh) / 1,000 requests
    = 0.1 gCO₂eq / request

Improvements can be achieved through lower energy (E), a greener region (I), or more efficient software (more R for the same E).

What IT Sustainability is NOT

Misconception	Reality
"We buy CO₂ offsets, so we are neutral"	Offsets are not a substitute for reduction. CSRD and SBTi require real reductions; offsets are a last resort for unavoidable emissions.
"Cloud is green, so our IT operations are green"	Cloud providers are increasingly operating their infrastructure with renewable energy — but the customer workloads determine how much of it is consumed. Inefficiency is inefficiency, whether in the cloud or on-premise.
"Sustainability means simply switching everything off"	Sustainability optimizes for CO₂ per functional unit (SCI) — not for absolute shutdown. The goal is to provide the same functionality with fewer resources.
"That is a topic for the CSR department, not for engineers"	CSRD, SBTi and ESG reporting require data from IT operations. Architects and engineers are the only ones who can generate this data — sustainability is an engineering topic.

Misconception

Reality

"We buy CO₂ offsets, so we are neutral"

Offsets are not a substitute for reduction. CSRD and SBTi require real reductions; offsets are a last resort for unavoidable emissions.

"Cloud is green, so our IT operations are green"

Cloud providers are increasingly operating their infrastructure with renewable energy — but the customer workloads determine how much of it is consumed. Inefficiency is inefficiency, whether in the cloud or on-premise.

"Sustainability means simply switching everything off"

Sustainability optimizes for CO₂ per functional unit (SCI) — not for absolute shutdown. The goal is to provide the same functionality with fewer resources.

"That is a topic for the CSR department, not for engineers"

CSRD, SBTi and ESG reporting require data from IT operations. Architects and engineers are the only ones who can generate this data — sustainability is an engineering topic.

Target Picture

A sustainability-mature IT organization:

measures emissions continuously per workload and service
operates compute energy-efficiently (ARM/Graviton, no idle resources)
chooses regions carbon-consciously and documents exceptions
minimizes data through consistent lifecycle policies
shifts batch jobs to low-emission time windows
reports CSRD-compliantly with automated data flows
manages sustainability debt in a quarterly-reviewed register

This target picture corresponds to maturity level 4 (Optimized) in the WAF++ Sustainability model. Maturity level 5 (Carbon-Neutral) additionally requires verified compensation or complete avoidance of remaining emissions.