Discs vs. data: Are we helping the environment by streaming?

Gone are the days of going to Blockbuster to pick out a film for a night in. Physical media like CDs, DVDs, Blu-ray discs, Sony’s weird PlayStation Portable UMDs, and countless other formats have been thoroughly dethroned thanks to a barrage of streaming services like Netflix—itself ailing at the moment—Amazon Prime, and Spotify.

For the first time in the past 17 years, CDs saw an increase in sales—of 1.1 percent, or 40.59 million units in 2021, compared to 40.16 million units the year prior. In 2021, people purchased 1.2 billion pieces of physical video media, compared to 6.1 billion a decade prior. Meanwhile, according to the Recording Industry Association of America, revenue from music streaming grew 13.4 percent to $10.1 billion in 2020.

Physical media might not be dead—there are still people collecting cassettes, and vinyl has made a small comeback—but streaming is the norm. Nostalgia aside, this isn’t exactly a bad thing, environmentally speaking. By and large, the energy and emissions that come from streaming a whole season of Seinfeld for the umpteenth time are lower than purchasing that same season from Best Buy.

However, any environmental benefits differ based on myriad factors, such as what time of day you’re streaming, which country you’re in, what you’re watching the content on, etc. Further, while it’s more eco-friendly to watch shows on Netflix compared to a disc, streaming has made media so available that these benefits can be lost due to repeated visits to the “binge-worthy” section.

To stream or not to stream?

Pinning down exactly how much better—under some circumstances—it is to stream a movie than to watch it on DVD is tricky. Many of the papers on the topic date back to the early- to mid-2010s, and things have changed since then. In one study, published in 2019, Aditya Nair—then a Michigan State University engineering student and now a full-time engineer—and his team performed a comparative life-cycle assessment between a Blu-ray disc and a Netflix movie. The paper resulted from an engineering class the team took, during which they could perform the comparative life-cycle assessment on whatever they wanted. At the time, in 2016, streaming services were well on their way to displacing physical media as the world’s delivery method of choice. “It was usurping physical movie watching, and that has only gotten more intense over the years,” Nair told Ars.

For the assessment, the team had to make certain assumptions. For one, it assumed that the viewer of the movie was in Ann Arbor, Michigan, (which matters because of the sources of energy that go into powering a TV and the distance a disc would need to travel, among other factors) and that they were either watching a DVD in 2011 or Netflix in 2017. The viewer also owned a typical LCD TV set.

A life-cycle assessment takes into account the energy and emissions (among other things) that go into these media, from creating the file or disc to watching it and (in the case of a disc) throwing the media away. For a physical disc, the assessment factored in the process of writing the file to the disc and packaging the disc, plus any energy and/or emissions that came from the retail process, purchase, and, ultimately, its use. For the digital file, the assessment only included server loading, file delivery, and use.

Four to one

Nair and his team collected data on the two delivery methods from previous life-cycle assessments, pieces of corporate reporting, and the EcoInvent database and ran it through a piece of life-cycle assessment software. The results were broken down according to the Tool for Reduction and Assessment of Chemicals and Other Environmental Impacts (or TRACI) metrics, made by the United States Environmental Protection Agency. These metrics included global warming potential (represented in kilograms of CO₂ or equivalent), ozone depletion (kilograms of CFC-11 or equivalent), and compounds produced that can cause respiratory issues (represented in PM2.5 or equivalent), among others.

Across all of the metrics, streaming a movie was less environmentally damaging than purchasing and watching a Blu-ray disc. In terms of global warming potential, the two delivery methods only reached the same impact when the viewer streamed the movie four times. “As a one-to-one replacement, we found that streaming was better for the environment than watching on a Blue-ray [disc],” Nair said.

Much of this comes from the simple fact that manufacturing a Blu-ray disc involves more steps and materials. In the case of streaming, over the course of a year, a solid 90 percent of the energy demand came from users operating the electronic devices and data transmission. Comparatively, only 12 percent of the physical option’s energy came from playing the disc—the rest came from manufacturing, according to the paper.

It gets tricky

Of course, this study looked only at Michigan, only at TV, and only at a specific set of years. According to Nair, it’s safe to say that the situation would be different now. For example, Michigan’s energy mix may have shifted, meaning there would be fewer emissions per disc or per watch. “If you’re streaming and all of your streaming is powered by solar, I’d assume the impact on the environment would be drastically different than a conventional natural gas-powered grid.”

Tomohiro Tabata, associate professor at Kobe University in Japan, performed a similar experiment in Japan. The results were published in MDPI in 2021. Rather than comparing hard media to streaming, he performed a life-cycle assessment on music and video streamed either through PCs or smartphones—and whether or not the service is a subscription or free.

For instance, on a computer, a subscription-based video-streaming service came to 1.57×10⁻⁴ kg of CO₂ per megabyte, compared to the same service on a smartphone, 1.40×10⁻⁴ kg of CO₂ per megabyte. Not surprisingly, cellphones produced fewer emissions relative to the amount of data used in the case of music services (and whether or not the streaming service was paid or free) than computers. In an email to Ars, Tabata noted that countries that produce electricity from fossil fuels and coal are likely to have higher emissions associated with producing and watching these kinds of media—and powering the servers that distribute them, in the case of digital.

According to Tabata, this kind of info could not be reliably calculated for physical media in the study. A number of factors needed to be considered, such as whether a disc is purchased new or secondhand, or even rented. “If hard media are not discarded and continue to be distributed as used products, then resource consumption is curtailed because there is no need to manufacture new hard media. This is an efficient way to reduce CO₂ emissions from hard media. However, it is difficult to determine how long hard media will be used throughout its life cycle,” he wrote.

Greener pastures?

At face value, it appears that streaming has a leg up on hard media. One paper from 2014 notes that when a customer bought a DVD from a store in 2011, the energy use per viewing hour was 2.5 megajoules per hour and 0.2 kilograms of CO₂ per hour more than streaming, Ars previously reported. However, Nair said that easy access to a huge array of movies and TV shows means that people may be watching more content online and are thus using more energy and producing more emissions.

“On a one-to-one basis… streaming can be better for the environment. But we have to consider that the changes in viewing behavior have been made, and I think a lot of those changes are here to stay,” he said. “With content being at your fingertips, it’s hard to take that away. Pandora’s box has been opened, so to speak.”

Another thing that’s changing is the quality of the media we’re using. A minute of HD video, which might have been the standard back when the studies were done, is only about 105MB of data. That rises to roughly 150MB for 1080p and 320MB for 4K video, meaning an hour of video could now mean 17 times the emissions. That’s larger than most of the margins seen in the earlier studies.