Paper, Plastic or Canvas??? This is a question we face with every trip to a store but what is the Best choice? It is easy to say that a reusable canvas tote is the best choice but is it really the best choice? Actual carbon-footprints vary depending on the sources of the bags. Recycled plastic bags are showing up in many markets. Most paper bags are post-consumer recycled paper (not usually from "trees" directly.) Canvas tote bags are costly(compared to plastic or paper) and are mostly made in China under questionable working conditions. When we add up the materials(new canvas), the construction(underpaid workers in bad working conditions), add a huge PLASTIC graphic on the side and shipping across the world, then canvas tote bags get very expensive for the environment and for humans.
To be the MOST eco-friendly, just re-use the bags you already have and save the environmental expense of making new tote bags. Double or triple the old plastic bags and double up on paper bags and they will last through a hundred shopping trips. Or, you could re-use a pair of old jeans and make a tote that will last as long as you do.
At the very least look for bags made of re-used materials (Canvas from sails or denim from old jeans maybe) by someone in your neighborhood.
Beware of any eco-friendly ideas that require the purchase of a new item! Every new item including tote bags require a manufacturing process that adds to the over all problem. Right now, being green is a fad that inspires people to buy more, more, more....in the future being green will mean buy less, use less, and use what you have until it is worn out. When you buy stuff you are feeding the FAD...when you actually start re-using what you already have then you are MAKING A DIFFERENCE!
BTW, I got my Free Tote Bag from Yahoo Answers and it arrived in a PLASTIC BAG and has a huge plastic graphic on the side and it is "Made in India"!