Low Carbon Computing - Detailed Notes

End User Premises

• Typical devices include:
  • PCs
  • Phones and tablets
  • TVs (described as black-box computers with large screens)
  • IoT devices
• Home networks utilize:
  • Wi-Fi
  • Bluetooth

Network Types

• Home network connects to the "internet" through:
  • Local wireless connections
  • Wired connections
  • Mobile networks (3G/4G/5G concurrently)
• Long-distance communication relies on optical connections.
• Data centers are a key part of the network infrastructure.

Cloud Data Centers

• Components include:
  • Servers
  • Rack switches
  • Network infrastructure
  • Cooling systems (using electricity and water)
  • Power supply
  • Physical infrastructure

ICT Sector Emissions Breakdown (Figure 10)

• Key emission sources in the ICT sector:
  • Data centers
  • Networks
  • User devices
• Emissions are measured in millions of tonnes of CO₂ equivalent (MtCO₂e).
• Emissions are categorized into:
  • Embodied carbon footprint
  • Use phase carbon footprint
• Reference: "Carbon impact of video streaming”, Carbon Trust report, 2021, reproduced from Malmodin (2020a).

Computing System Breakdown

• Focus on breaking down the components of a computing system to understand their carbon impact.

Chips

• Carbon cost factors:
  • Process node (older nodes have lower costs)
  • Number of layers (more layers increase cost, especially in 3D SSDs)
  • Chip area
  • Type (logic, RAM, SSD)

Chip Types

• CPU: predominantly logic-based and large in size.
• RAM: simpler manufacturing process but also large.
• SSD: 3D stacked, leading to significant size.
• GPU: similar characteristics to CPUs.
• NICs (Wifi, wired, Bluetooth): relatively small.

Other Components

• Key components include:
  • Motherboard
  • Hard drive
  • Battery
  • Power supply
  • Screen
  • Casing

Servers and Data Centers

• References:
  • Life Cycle Assessment of Dell PowerEdge R740 (thinkstep for Dell Technologies, 2019)
  • "The Datacenter as a Computer: Designing Warehouse-Scale Machines" by Barroso, Hölzle, and Ranganathan (Springer, 2019)
• Emissions from server use are roughly equal to emissions from manufacturing.
• Embodied carbon primarily comes from SSDs.

Phones and Tablets

• Emissions from production dominate the life cycle.
• ICs (integrated circuits) are the main contributors to emissions.
• Studies and data:
  • Louis-Philippe P.-V.P. Clément et al., "Sources of variation in life cycle assessments of smartphones and tablet computers", Environmental Impact Assessment Review, Volume 84, 2020

Carbon Footprint Assessment

• University of Glasgow, School of Computing Science.
• Wim Vanderbauwhede, Professional Software Development (H) COMPSCI4015.

Emissions Scopes

• Overview of different emission scopes for carbon footprint assessment.

Greenhouse Gas Protocol

• Established in 2001 by the World Resources Institute (WRI) and World Business Council for Sustainable Development (WBCSD).
• Provides a standardized framework for measuring and managing emissions.
• Divides emissions into four categories: scopes 1, 2, 3, and 4.

Emission Scopes Diagram

• Scope 1: Direct emissions (company facilities, vehicles).
• Scope 2: Indirect emissions from purchased electricity, steam, heating & cooling.
• Scope 3: Other indirect emissions (upstream and downstream activities).

Scope 1: Direct GHG Emissions

• Covers emissions from owned or controlled sources.
• Examples: combustion in boilers, furnaces, vehicles, chemical production equipment.
• Excludes direct CO₂ emissions from biomass combustion (reported separately).
• Excludes GHGs not covered by the Kyoto Protocol (e.g., CFCs, NOx).

Scope 2: Electricity Indirect GHG Emissions

• Emissions from the generation of purchased electricity.
• Occur at the facility where electricity is generated.
• Organization is indirectly responsible due to energy consumption.

Scope 3: Other Indirect GHG Emissions

• Includes emissions from upstream and downstream activities.
• Consequence of company activities but occur from sources not owned or controlled by the company.
• Examples: extraction and production of purchased materials, transportation of purchased fuels, use of sold products and services.

Scope 4: Avoided Emissions

• Emission reductions that occur outside a product's life cycle or value chain due to the use of that product.
• Examples: low-temperature detergents, fuel-saving tires, energy-efficient ball-bearings, teleconferencing services.
• Alternative terms: climate positive, net-positive accounting.

Assessment Standards

• Overview of relevant standards for carbon footprint assessment.

ISO Standards

• ISO 14040 and ISO 14044: Life cycle assessment.
• ISO 14067: Carbon footprint of products.

UK/EU Standards

• ILCD (EU): International Reference Life Cycle Data System handbook for detailed LCA studies.
• PAS 2050 (UK): Greenhouse gas emissions calculation method for goods and services.
• PAS 2060 (UK): Requirements for achieving and demonstrating carbon neutrality.

ITU-T Recommendations

• ITU-T L Suppl. 52: Computer processing, data management, and energy perspective.
• ITU-T L Suppl. 53: Guidelines on the implementation of environmental efficiency criteria for artificial intelligence and other emerging technologies.

ITU-T Recommendations (Continued)

• ITU-T L Suppl. 55: Environmental efficiency and impacts on United Nations Sustainable Development Goals of data centers and cloud computing.
• ITU-T L.1333: Carbon data intensity for network energy performance monitoring.

Server Footprint Calculation

Server Footprint Calculation Details

• Total CO₂ = embodied CO₂ + CO₂ from use
• Embodied CO₂ = Sum of emissions from manufacturing of all parts.
• Accurate figures are hard to find, but the Boavizta model provides a good estimation.

Server Footprint Calculation - Usage

• Assuming a server in a data center:
  • Server CO₂ from use = lifetime * electricity consumption * electricity carbon intensity
  • Data center overhead (mostly cooling) is expressed as PUE (Power Usage Effectiveness, a number > 1)
  • Total CO₂ from use = PUE * server CO₂ from use

Example: Dell PowerEdge R7515

• Embodied carbon: 1400 \text{ kgCO₂e}
• Electricity consumption: 415 \text{ kWh/year} (medium load)
• Carbon intensity:
  • UK: 182 \text{ gCO₂e/kWh}
  • Glasgow: 30 \text{ gCO₂e/kWh}
• Lifetime: 4 years
• PUE: 1.5 (quite good)
• Total:
  • UK: 1853 \text{ kgCO₂e}
  • Glasgow: 1475 \text{ kgCO₂e}

Longer-Term Factors

• Energy efficiency increases by about 1.2x per year.
• Carbon intensity decreases rapidly.
• Every replacement increases the embodied carbon.
• Question: What is the optimal lifetime of a server?

Sustainable Software Development

Software Development Considerations

• Importance of full-system methodology:
  • What emissions are incurred as a result of deploying the code in its current state?
  • Does the application result in emissions avoidance?
• What are the key contributors to energy usage and embodied carbon?

Software Development - Factors

• Disk utilization: local dev environment, git repo (E)
• CPU: local build cycles, IDE; cloud CI/CD (E,U)
• RAM: local build cycles, IDE; cloud CI/CD (E,U)
• Networking: local/cloud communication (E,U)

Software Deployment

• Disk utilisation: application, local storage, cloud storage (E)
• CPU: local compute, cloud compute (E,U)
• RAM: local compute, cloud compute (E,U)
• Networking: local/cloud communication (E,U)

Tools and Resources

• Low Carbon Computing Resources:
  • Papers, articles
  • Tools, APIs, SDKs
  • Courses
• Detailed embodied carbon calculation model