Unused digital data is an invisible yet significant issue which consumes substantial amounts of energy and resources, writes Dr Erivelton Nepomuceno of the Hamilton Institute, Centre for Ocean Energy Research and Department of Electronic Engineering.

    In an age where snapping a photo is as easy as a tap on a screen, it's fascinating to reflect on the rituals of photography in the past when it used to be a formal occasion.

    Friends and relatives would prepare for a portrait, carefully positioning themselves, adjusting the lighting and ensuring everything was just right. When the command to "say cheese" was given, everyone was ready with a smile. It was a moment of breath-holding, hoping no one blinked or moved. Photos were little treasures, proudly displayed on walls or kept in albums.

    Today, the landscape of photography has transformed dramatically. With smartphones and digital cameras around, taking photos is super easy and just part of everyday life now. We capture countless moments, from simple scenes to great events, often without a second thought. These photos, along with videos, are stored digitally, predominantly in the cloud. This shift has made it easier to take and keep an immense number of images, but it also means that many of these digital memories remain unseen and unused.

    Unlike plastic waste, which is visible in rivers and oceans, unused digital data is an invisible yet significant issue. The vast amounts of data stored in the cloud, much of it never accessed or used, contribute to a growing problem. This storage consumes substantial energy and resources, making it unsustainable to store all data indefinitely. Approximately 10% of a data centre's electricity bill is attributed to hard drive storage. Although it's significantly less than the energy consumed by servers, hard drive storage still uses about 20 TWh annually, which is comparable to the total electricity generated by Iceland or Tunisia.

    Researchers have categorised data into three main types: business-critical data, obsolete, trivial and redundant data, and dark data. Business-critical data includes things like customer information, financial records, and operational data—essential for running a business. Obsolete data, on the other hand, includes outdated reports, duplicate files, and irrelevant emails, which often waste energy and resources without providing any real benefit. Even worse is "dark data", unused data that's saved but never accessed. This includes all those photos and videos we keep but never look at.

    Storing each terabyte of data in the cloud produces about 10 kilograms of CO₂ equivalent per year. To put that into perspective, it is comparable to driving 50 km in a typical car. In fact, data storage is just one part of the tech sector, which accounts for approximately 1.8% to 2.8% of global greenhouse gas emissions. Data centres alone contribute around 100 million metric tons of CO₂ equivalent annually, comparable to the emissions from the entire US commercial aviation industry.

    Green computing—or sustainable computing—offers a proactive approach to reducing these effects by emphasising the design, use and disposal of technology in eco-friendly ways. Originating with the US EPA's Energy Star program in 1992, green computing focuses on improving energy efficiency and minimising environmental damage.

    Key strategies include optimising software, managing data centres and improving data storage practices. With the rise of energy-intensive technologies like AI, cryptocurrency mining and networking equipment, green computing also highlights the importance of efficient coding and energy-efficient devices to advance a more sustainable technological future.

    Leading tech companies like Nvidia and IBM are actively working on green computing initiatives to reduce carbon emissions and promote sustainability in the tech industry. By adopting these practices, the goal is to create a more sustainable future while continuing to innovate and advance technology.

    But green computing isn't just for large organisations and individuals can also contribute to tech sustainability. Simple actions like using hibernate or sleep modes, adjusting screen brightness and turning off devices when not in use can significantly reduce energy consumption. Refilling printer cartridges and purchasing refurbished equipment help minimise waste, while proper disposal of electronic devices enhances both sustainability and security.

    Whenever possible, opt for energy-efficient devices, such as laptops instead of desktops, and look for Energy Star ratings when buying new equipment. You could also try keeping only the best photos and deleting the rest. This helps reduce digital storage needs.

    Broad societal engagement is essential, and this issue shouldn't be underestimated. Dr Vitor Castro and his team at Loughborough University warn that the expansion of renewable energy might not keep up with the growing electricity demands of the digital data sector. This shows the tricky balance between digital growth and environmental sustainability.

    Castro's latest findings highlight the need for a data-focused sustainability approach across all sectors. These steps are crucial for boosting efficiency, cutting energy use, and creating a greener, decarbonised digital ecosystem. It's a reminder that we all have a role to play, inspired by figures like Ken Saro-Wiwa, Severn Cullis-Suzuki and Chico Mendes.

    This piece originally appeared on RTÉ Brainstorm