Though you probably know that Friday is Earth Day, I'd wager that you weren't aware that it's also National Cell Phone Recycling Week. Created two years ago by the Environmental Protection Agency, the week encourages U.S. wireless subscribers to recycle and reuse old handsets rather than discarding them into a drawer, or worse yet, throwing them away in the trash.

It's a noble effort, indeed, particularly when you consider how often we're encouraged to trade up for the latest and greatest phone. Sure, e-waste is a concern across the gadgetsphere, but the shelf life of a cell phone can last only months and the stream of new models never seems to stop. And when you add in harmful materials like lead, mercury, cadmium, and arsenic that can end up in the environment, it's not a pretty picture. Fortunately, though, recycling your handset is much easier than trying to get rid of your flat-screen television. In fact, you can do your part without even leaving your house.

For this post, I rounded up and evaluated the recycling efforts of the major carriers. As you'll see from the list, some carrier programs offer incentives, whereas others give you just the peace of mind that you kept one more phone out of a landfill. Doing a good deed may be enough for some, but I recognize that other readers will enjoy an extra benefit. Also, keep in mind that many other recycling options are available. They can include your phone's manufacturer, your employer, a local government agency, a third-party retailer (like Best Buy), or a nonprofit organization. For local drop-off points, check out this helpful site from Call2Recycle.

Currently, only about 1 percent of phones are recycled in the United States so the numbers can only improve. Before you recycle, however, there are a few points to remember.

Though carriers offer recycling programs, they aren't actually operating the program themselves. Instead, they partner with reputable companies like ReCellular that do the dirty work.

Carriers will promise to wipe your phone of any personal information, but it's essential that you take that step yourself. A "factory reset" is a great place to start, since it will clear your phone's data and return it to the same condition as when you bought it. If your phone doesn't have such an option (and even if it does), make sure to remove all text messages, photos, applications, e-mails, and contacts. Also, delete your call timers and your recent calls list.

If you don't trust yourself to wipe your phone's memory properly, there are a few data third-party options that promise to do the job for you. I haven't used any personally, but ReCellular offers a tutorial on its site.

Drain your phone's battery completely, but leave it in the phone. If sending extra batteries, tape over their connection points.

Remove your SIM card and any memory cards.

Make sure to cancel your account or switch your number before you recycle the phone.

One of two fates will await your phone, though you won't have a choice of which one it will meet. If refurbished, the handset will be spruced up and either donated to a charity or resold by the carrier or a third party. If it's recycled, the handset will be salvaged for useful parts with the rest of the materials going to an eco-friendly disposal. Any valuable parts can then be reused in another gadget.

If going green is a top concern, why not consider a handset like Verizon's Samsung Intensity II It's made from recycled materials, the package is partially printed with soy ink, and the box is smaller and is composed of 60 percent recycled paper.

For more resources, check out these consumer sites from the EPA and CTIA.

Sprint As Sprint is eager to tell you, Newsweek listed it last October as the sixth greenest company in the United States. And to its credit, the carrier beats its rivals in ways to put an old phone out to pasture. With the Buyback Program, new and existing customers will receive account credit when they trade in a used handset. You then can apply the credit toward your monthly bill or the purchase of a new phone.

Not every device is eligible, but the long list of approved phones and tablets includes models that Sprint doesn't carry. For example, a 64GB Wi-Fi iPad will earn you $195, a T-Mobile MyTouch 4G is worth $85.69, a Samsung Restore brings $26, and an LG EnV Touch delivers $12 in account credit. Normal wear and tear is fine, but the product must turn on and be free of corrosion, water damage, and display scratches.

To participate, you can visit a Sprint store (where you'll get your credit instantly) or print a shipping label online . If you use the latter method, Sprint will pay for postage though it will take a few weeks for a credit to post to your account. Once received, the device will either be refurbished or recycled. For more on the Buyback Program, check out Sprint's FAQ.

If your phone isn't on the list of eligible devices, you can send it in for recycling through Sprint's Project Connect. Sprint will accept all phones in any condition, plus accessories, chargers, extra batteries, packaging, and user manuals. Prepaid shipping labels are available online or you can find them at Sprint stores and inside the box of most of the carrier's current handsets. Proceeds from the sale of parts will go to organizations like the National Center for Missing & Exploited Children, Boys & Girls Clubs of America, and the National Education Association Health Information Network.

Verizon Wireless Big Red also offers credit for old devices through its Trade-In Program. The process is very much like Sprint's program: first you select your device, denote its condition, and print the free shipping label. Then, just send on its way and wait for a Verizon gift card with the corresponding credit.

Verizon also accept a broad range of phones and tablets, including devices that it never sold. The list is comparable to Sprint's, though credit will vary widely. For example, a 64GB Wi-Fi iPad has an appraised value of $175, a Samsung Restore is $1, a T-Mobile MyTouch 4G is $112, and an LG EnV Touch is $30. If your display is cracked or the device doesn't power on, you'll get just a couple of dollars if you get anything at all.

Alternatively, Verizon's HopeLine program also will accept all phones for either reuse or recycling. Refurbished phones won't go back to Verizon, but will be donated along with 3,000 minutes of wireless service to domestic violence organizations. To donate a device, you can print a prepaid shipping label online. And if you just have a battery to dispose of, the carrier has a separate program through the Rechargeable Battery Recycling Corp.

AT&T Through AT&T's Reuse and Recycle Program, you can recycle an old phone by dropping it off at an AT&T store. The carrier will accept all types of handsets as well as accessories and extra batteries.

You also can recycle used handsets through the Cell Phones for Soldiers program, which uses funds from donated cell phones to buy prepaid calling cards for active-duty military personnel. Prepaid shipping labels are available at company-owned stores or online.

Virgin Mobile When you buy a new Virgin Mobile phone, the carrier will accept your old device for reuse or recycling. Refurbished handsets will then be sold to new Virgin Mobile customers or sold at a reduced rate to, as Virgin puts it, "people who are in need of a mobile phone." On the other hand, profits from recycling efforts will got to charitable partners.

Another option is the Pass it On program. After you buy a new Virgin Mobile phone, you can pass on your old handset to a friend or even a stranger (after transferring your number, of course). When that person activates the phone to their account, you'll receive 60 minutes in calling credit.

Boost Mobile Boost will recycle your phone with proceeds benefiting Global Inheritance. All models in any condition are accepted and you can get a prepaid shipping label on Boost's site.

U.S. Cellular Though it doesn't offer a dedicated green page on its Web site, U.S. Cellular will recycle any wireless phone that you bring to a carrier-owned store.

T-Mobile If you're a T-Mobile customer, the Handset Recycling Program will be your only option, though the carrier will accept all wireless devices and accessories in any condition. T-Mobile stores will take donations or you can print free shipping labels online (PDF).

MetroPCS With MetroPCS' EcoSave Program, you can bring old phones, batteries, and accessories to any MetroPCS store for recycling.

Cricket Wireless Cricket partners with ReCellular to recycle or refurbish phones. You can get the shipping labels on Cricket's site or drop off your devices at the carrier's retail stores.