Even with its bandwidth costs, video can be more environmentally friendly than movies on DVDs, according to a research paper published Wednesday at IOP Science. The authors found that the emissions and energy consumption for DVD watching are higher altogether than for streaming video, all things considered, so ditching the plastic discs may be the most conscientious direction to take.

The authors looked at several possible distribution methods for DVDs, including transporting them to stores or warehouses; repackaging them for the store or rental business in question, if necessary; and then delivering them to their final destinations. The study also accounts for the efficiency and power use of DVD playback devices, including computers and game consoles, as well as the energy consumption of watching the DVDs on monitors or televisions.

Across the whole category, the researchers estimated that 1.2 billion DVDs were purchased or rented over the course of the studied year (2011), with an average disc lifetime of three years for rentals and five years for purchases. Each disc and case was estimated to embody about 1.5 megajoules of energy, and about 58 grams of CO 2 .

Assumptions for calculating the impact of streaming videos included storage on servers and all of the transmission equipment, including routers, cable boxes, playback devices like a set-top box, and viewing devices like a TV. For the data centers storing the video, the authors assumed that they worked roughly like "cloud data centers" where server use scales with demand.

The study estimated that streaming video clocked in at about 3.2 billion hours and 26.2 petabits of data for 2011, with an average power per server of 300 watts and 1,400 servers in use to meet demand at the time.

The authors also had to make estimations about the device use breakdown for each activity. They used figures stating that 90 percent of DVD watching takes place on a TV, with 14 percent of that 90 using a video game console of some kind and 76 percent using a DVD player. Streaming was assumed to take place on a gaming console about half the time, with set top boxes making up another 21 percent, and only 20 percent between desktop and laptop computers.



All told, the study's estimates showed that streaming barely has a hold over DVDs bought and shipped in the mail and is actually beaten by DVDs rented by mail in terms of efficiency and CO 2 emissions. When a customer goes to purchase DVDs from a store, however, the energy use per viewing hour is about 10 megajoules, a scant 2.5 megajoules per hour and 0.2 kilograms of CO 2 per hour more than streaming. DVDs rented from a store were the worst offenders, using 4 megajoules and causing 0.3 kg more CO 2 emissions per viewing hour, but good luck finding a store with DVDs these days to commit your emission and energy crimes in.

If all DVD usage as studied in 2011 were to roll over to 100 percent streaming, both emissions and energy use would be lowered. The study suggests that a 100-percent video-streaming-oriented market would result in an emissions savings of 2 billion kilograms of CO 2 over 20.4 billion viewing hours, roughly the equivalent of one 300-megawatt coal-fired power plant. The energy savings would be around 30 petajoules, the equivalent of about 716,000 tons of oil. However, most of those savings come from ending the brick-and-mortar store visits that consumers make to get DVDs, less so from DVD creation or playback itself.

While the study showed that the conversion to video streaming would be universally better for a fixed amount of video consumed, it did not speak to how availability of video might affect that quantity. Part of the appeal of video streaming is that it's very accessible and often free, whereas video distribution via DVD is more constrained. Even if watching a YouTube video is more efficient and environmentally friendly than watching a DVD, one does not often get lost in a time vortex watching a DVD for four straight hours. YouTube, on the other hand…

IOP Science, 2014. DOI: 10.1088/1748-9326/9/5/054007