Why Green Software Matters

Software is everywhere, and its development and operation consume an increasing share of our world’s energy and other resources. It’s the invisible engine that powers our modern world, from weather forecasting to streaming entertainment. But this incredible power comes at a cost — its development and operation consume increasing amounts of resources. While digitalization offers many possibilities, the environmental impact of software shouldn’t be ignored. Many industries, communities, societies, and nations are still at the beginning of their digitalization journeys, so the demand for software will continue to grow, as will its footprint on our planet. This trend is unsustainable. We know that climate change is a major global problem, and every discipline should contribute to solving it.

But hold on, you might say, doesn’t digitalization also make us much more efficient and will even help us solve the climate crisis? I (partially) agree. Online meetings are less carbon-intensive than flying to in-person meetings.¹ Reading books on e-readers is often better for the environment, as Mike Berners-Lee, a researcher who pioneered carbon accounting and footprinting has calculated: “You have to read the equivalent of at least 36 paperback books (bought new, then recycled) in e-book format before the paper saving outweighs the emissions embodied in the device.”² So, there are ways in which software and digital can help us reduce our carbon footprint. All is good then, right?

But we have to be careful not to fall into the trap of rebound effects and Jevons paradox: when something becomes more efficient or cheaper, we tend to use or do more of it. For example, more fuel-efficient cars lead to more kilometers being driven overall. So just using more software and producing and transmitting exponentially more data every year is not a solution in itself and certainly won’t heal our planet. Consider the size of websites: “[..] between June 2012 to June 2022, the median page weight increased by [..] 594%, or 1.7 MB for mobile page loads”, Web Almanac reports. Of course, telecommunication networks have also become more efficient. A study by Nokia found that 5G is 90% more energy-efficient than 4G. So what about average Web page loading times? These have gone up, so even our faster and more efficient networks can’t keep up with the increased page sizes — an excellent example of the Jevons paradox. There is a flip side to the increased use of digital solutions, so we should consider the sustainability of the software and how we use it. Because something is digital and seemingly lightweight, it doesn’t mean its environmental footprint is low and can be neglected.

A study by Charlotte Freitag and colleagues estimates that the global emissions of the Information Communication Technology (ICT) sector could already be as high as 3.9%. These calculations include components such as data centers, networks, and end-user devices. These ICT emissions cover the whole hardware lifecycle, from manufacturing and operations to disposal. During operation, the software has a significant influence on the amount of energy that is used. So, in addition to using electricity from sustainable sources, one step towards sustainability is to minimize the energy consumption of the underlying hardware caused by software, including processing (CPU, RAM), storage (hard or solid-state disks), and network devices. The EU recently published a technical report on the Energy Consumption in Data Centres and Broadband Communication Networks in the EU, supporting these numbers. They estimate that “the combined energy use of data centres and telecommunication networks in the EU was 70–95 TWh in 2022, equivalent to 2.8–3.8% of total regional electricity use.” One country uses 18% of its electricity for data centers — can you guess which one?³

Several initiatives have sprung up in recent years, and terms such as Green/Sustainable Software or IT are entering the mainstream of the software community through conference talks, articles in professional magazines, blog posts by major cloud providers, and so on. The vision of the Green Software Foundation, for instance, is to “change the culture of building software across the tech industry, so sustainability becomes a core priority to software teams, just as important as performance, security, cost and accessibility.”

With this blog, I want to contribute to reaching this goal. Hi 👋, my name is Mirko. Computers, particularly software, have fascinated me for as long as I can remember. I have been in the industry for a quarter of a century now and worked on a broad range of software systems. I love programming languages and tinkering with new technologies, something that our industry is very efficient in churning out regularly.⁴ Lately, however, I have been thinking more and more about the sustainability of our profession. I read books and many research papers, tried out tools, listened to podcasts, and discovered that there is already a lot going on, more than I imagined. That’s awesome, but the problem is also enormously big, and it isn’t easy to figure out where to start. For example, do we even know how much energy running software consumes? How clean or dirty is that energy? How much carbon emissions does an e-mail cause (transmitting and storing it — probably indefinitely — in at least two accounts)? What about the hundreds of gigabytes⁵ of photos accumulating on our devices and backed up to the cloud?

I fear I don’t have answers to all these questions, but I want to try to figure it out and take you, dear reader, along my journey to discover how we can grow green software. I have planned a colorful bouquet⁶ of posts, some concerning more fundamental topics like emissions or measurements, to summaries of research papers to find out what we actually know and don’t know as well as experience reports with various tools and demos of APIs that we can use to make our software greener. If you are developing software and are concerned about the environment, I hope you will find this blog interesting and inspiring.

Figure 1: Overview of topics that we (briefly) touched in this post. This mind-map will grow with future posts.

Subscribe to this blog and let me know your questions and topics you’d like to see covered. You can also find me on @stocker@mastodon.social and LinkedIn.

A big thank you to my two colleagues Olaf and Stefan for their feedback and encouragement, which helped me to start blogging again.

1. Such direct one-to-one comparisons can be misleading. The alternative to online meetings isn’t always flying; sometimes, you just have to go to the offitheirce next door. And don’t we have too many meetings anyway?
2. In case “Berners-Lee” rings a bell, he’s the brother of Tim Berners-Lee, who invented the World Wide Web.
3. It is Ireland, where many “big tech” companies such as Amazon, Facebook, and Google are based.
4. What’s also fascinating is that with every new trend, such as cryptocurrencies or artificial intelligence, the demand for energy and hardware increases tremendously. Apparently, OpenAI’s Sam Altman is trying to raise $7 trillion (yes, that number has 12 zeros) for a new AI hardware company.
5. Since having children, the number of photos has just exploded. Speaking of which, this blog deliberately avoids decorative photos that only waste bandwidth.
6. I promise not to go overboard with gardening metaphors, although I do enjoy gardening. I will also try to keep those footnotes in check…