First, a suggestion (and we don't mean to sound snotty): It should be plain as the nose on your face that the answer is a hankie. That's right, the reusable, foldable square of cloth your grandpappy has carried around for decades. It may need a good washing every now and then, but you won't be producing a mountain of trash every time you have a cold.
If you've absolutely got a hankering for a paper-based blower, look for products made with recycled content -- especially post-consumer content. Many facial tissues are bleached to make them white and purdy, but as with many beauty products, this process involves the use of harmful chemicals that you really don't want ending up in your air or water -- let alone rubbed on your face. So look for products labeled totally chlorine-free (TCF) or processed chlorine-free (PCF). Here's a handy wallet-sized guide [PDF].