Perfectly good question, I've been wondering about this too. Laugh all you want, but if you're not going green, you're a part of the problem. I try to be less of a problem every day...
I don't know the answer to this, although it seems that tubes are made of many materials (glass, metal, plastic, etc.) that could potentially be recycled. What's the deal with the tube manufacturing process? Why are tubes predominantly coming from Russia and China? Is there something environmentally unsound about the way in which they are manufactured that has resulted in none of them coming from the USA, even with the USA's fairly behind-the-times environmental regulations?