Why Not Composite Decking?

What makes composite decking so environmentally friendly on the material-sourcing and manufacturing end also makes it unsustainable on the installation and end-of-life side. When you mix an industrial material (plastic) that is recyclable with a biological material (wood) that is compostable you get a material that is neither recyclable nor compostable. That is what William McDonough and Michael Braungart call a "monstrous hybrid" in their groundbreaking book Cradle to Cradle: Remaking the Way We Make Things. As a result, any sawdust or construction scrap is destined for the landfill. Since perfect collection of sawdust is nearly impossible a mitre saw will spread plastic/wood sawdust throughout the construction site. If your deck uses 100 twelve-foot boards and you are averaging three cuts per board with an 1/8-inch saw blade you will produce 8 pounds of this monstrous hybrid, a significant portion of which may blow away in the wind. It is also estimated that at least 100 pounds of scrap will go to the landfill, even after you make as many composite birdhouses as you can.

-Source: TreeHugger.com