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Sustainable Computing

My area of research interest could be broadly called “sustainable computing”, which I am actively pursuing in the Department of Engineering Science at the University of Oxford. I maintain this page as a set of resources about sustainable computing that I find useful.

What is sustainable computing? #

Sustainable computing concerns the consumption of computing resources in a way that means it has a net zero impact on the environment, a broad concept that includes energy, ecosystems, pollution and natural resources.

I consider that individual impact on the environment rounds to zero because although some people will change their behaviour, most won’t. This means that systems need to change. Energy production, transportation, manufacturing, agriculture. The transition to sustainability needs to be done on behalf of the individual by the system and at a large scale, so individuals can benefit from that change by default.

In computing, this means the organisations responsible for manufacturing components, building equipment, writing software, operating data centres, and running networks have responsibility for achieving sustainability.

Sustainability strategies in computing tend to focus on energy and the transition to renewables – the use stage. This is important, but not the only factor.

Sustainable computing therefore involves not just renewable energy, but also minimising water stress, developing policies around the right to repair and recycling of materials through a circular economy, energy efficiency of hardware and software, promoting good governance of resources, transparency, and consistent reporting.

Articles #

Communities #

  • ClimateAction.tech. I subscribe to this weekly newsletter because it provides a good summary of interesting news, events and podcasts related to what the technology sector can do to help climate change. I’m not in the Slack group though because I try and avoid group chat where possible.
  • Green Software Foundation. A group of technologists (primarily from commercial organizations) working on standards and best practices to help software developers build more sustainable software.

Data #

Interesting sources of data related to sustainable computing:

  • Cambridge Bitcoin Electricity Consumption Index. The headline figure is 97 TWh of annualised energy consumption, but with a range of 35 TWh – 364 TWh. However the missing context is how that electricity is generated. Distinguishing between whether that came from fossil fuels or renewables is important (39% renewables, primarily hydro), particularly as governments impose stricter regulations which may have unintended negative effects (such as increasing carbon intensity of mining). Whether it is possible to move to a proof-of-stake implementation, like Ethereum, is also important.
  • Carbon free energy for Google Cloud regions. Google is the leader in sustainable cloud computing. They have done the most work and made the most progress at reaching carbon neutrality, then 100% renewables matching, and have a goal to hit 24/7 renewables by 2030. They are less transparent on water consumption, but do publish data on their carbon free energy percentage for each GCP region.
  • SPECPower database. The Standard Performance Evaluation Corporation (SPEC) provides quarterly test results of the power and performance of the latest single and multi-node servers. By simulating workloads, this data shows the average power consumption (in watts) at 100% and idle load. The difference between the two is known as power proportionality – does the server reduce its power consumption in proportion to the load – a ratio which has been improving over time. This data is used as part of the cloud carbon coefficients project to provide estimates for the power consumption of popular cloud computing CPUs for use in the Cloud Carbon Footprint project.

Papers #

Here are the most important academic papers related to sustainable computing, but I also publish notes about papers I read:

See also my own publications and Sources of data center energy estimates: A comprehensive review Joule (2022) in particular.

Reports #

Interesting reports related to sustainable computing:

  • 24/7 by 2030, Google (2020) This describes the challenges with procuring 100% renewable energy and why 100% doesn’t actually mean 100%. It shows how this relates to data centers and the path towards achieving it. Google is leading the industry in this regard, but there are challenges for the energy system.
  • Carbon impact of video streaming. 2021, Carbon Trust This is the most accurate analysis of the energy and carbon footprint of video streaming. It was written through an industry partnership with Netflix, so uses validated data, but based on academic models through work done at the University of Bristol. It provides a clear description of the conventional approach to calculating network energy using average intensity, but also describes an important new power model. See my discussion in Measuring website energy consumption via browser profiling.
  • Clicking Clean Virginia, Greenpeace (2019) Greenpeace are often seen as extremists but they do a good job of raising awareness. In this report they attempt to estimate energy consumption of data centers in Virginia, US, particularly those used by cloud providers like Amazon, Google and Microsoft. They use FOI requests to obtain local permits for facility sizes and then estimate the total energy demand depending on the size of the data center. The energy supplier for Virginia is notorious for using fossil fuels and so Greenpeace does a good job of laying those alongside the “100% renewable energy” claims made by the big providers. See also: How can data centers use 100% renewable electricity?
  • Digital technology and the planet, Royal Society (2020) A wide-ranging report from the Royal Society. Chapters 2 and 3 are of particular interest in relation to better disclosures and the impact of technology use.

Tools #

Interesting tools related to sustainable computing:

Other #

  • Awesome Green Software: A list of dev/tooling, organizations and research/articles about how software developers can approach building software in a more sustainable way.
  • Adrian Cockcroft’s talk at Monitorama 2022: Recently retired AWS VP, Sustainability, Adrian Cockcroft, gave a good 30min talk at the Monitorama 2022 conference: where he summarised the state of cloud carbon sustainability. Nothing new if you already know the topic, but a great intro to the current state of things.
  • Hot Carbon 2022: A conference/workshop all about sustainable computing, with videos and papers for most of the talks.
  • Principles of Green Software Engineering: A set of principles for software engineers to keep in mind when writing software to try and reduce its environmental impact (which usually means carbon, but isn’t limited to that being the only measure).