Feature

CDs versus USB flash drives

G Magazine

Which portable data storage device is greener?

USB flash drive

Credit: iStockphoto

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Just what is the most environmentally responsible way to save your files?

Is it the older and bulkier CD or the newer, smaller USB flash drive (aka thumb drive, keychain drive, jump drive, pen drive and USB stick)?

Making it

The main component of a CD is petroleum-derived polycarbonate, a lightweight and break-resistant plastic.

Although plastic isn't considered green, in April of 2008, Toshiyasu Sakakura, a chemist with the Japanese National Institute of Advanced Industrial Science and Technology in Tokyo, announced that he had discovered a chemical pathway that turns carbon dioxide into polycarbonate or other plastics.

So CDs made from captured carbon dioxide might be a thing of the future.

The tiny size of a microchip inside a USB flash drive belies its environmental impact. Fabricating something so intricate requires very pure raw materials and a lot of energy to maintain that purity.

In 2002, scientist Eric Williams, from Arizona State University in the US, looked at the manufacture of a 32-megabyte microchip, similar to that found in a USB flash drive.

The 2-gram microchip required 72 grams of chemicals, 1.2 kg of fossil fuels, 32 kg of water and 700 g of gases to produce.

While microchip fabrication is becoming more efficient, the demand for more storage per chip means the amount of materials used in manufacture will remain steady over the years.

Capacity

It's hard to say which technology can store more files, as the two leapfrog each other with each techno-development.

One or two gigabyte (GB) USB flash drives are now ubiquitous, with 16 and 32 GB devices available at the top end of the market.

CDs can store of around 700 MB, while DVDs can store about 5 to 8 GB, or about six episodes of your favourite one-hour TV show.

The next improvement in optical storage is blu-ray technology, providing 25 to 50 GB of space per disc.

The USB data storage industry is worth roughly two thirds of its counterpart, but it's likely that it will overtake CDs and DVDs in the future.

A USB flash drive can survive 10,000 write/rewrite cycles, but the USB plug will only survive about 1,500 connections. On the other hand, you can use a rewritable CD about 1000 times before it gives up the ghost.

Unfortunately, rewritable CDs never gained widespread popularity because USBs came along, and people have favoured CDs more for permanent file storage.

Using ... and reusing

Of course, you can't use a CD or USB flash drive by itself.

A USB flash drive needs a USB port, which all new computers have. A USB flash drive has no moving parts, so it uses a negligible amount of energy to run the warning light and store energy when it's connected to the port.

But to store information on a CD, you need a CD drive, which requires a small motor to spin the CD and move the laser. Such a drive takes almost one watt of power when running, and accounts for one per cent of the energy (about 13 kWh) required to manufacture a PC.

Because of the mix of materials, especially metals, both CDs and USB flash drives are difficult to recycle.

This is true of most electronic waste, which makes up nearly five per cent of all solid urban waste worldwide - almost as much as plastic packaging.

A shallow victory?

There are no good figures available for the detailed environmental impact of these electronics, but in general, the USB drive is ahead by a nose: a lot goes into its manufacture, but it will get more use and doesn't require a special drive.

However, while a USB flash drive is more environment-friendly than a CD, like most electronic gadgets, it's still far from being green.