Here's some more information regarding plastic and landfills:
Earth’s Oceans: Our Largest Plastic Landfills axisoflogic.com/artman/publish/Article_58030.shtml
Recycling 1 ton of plastic saves 7.4 cubic yards of landfill space.earth911.com/recycling/plastic/plastic-bottle-recycling-facts/
When a plastic bottle enters a landfill, it can take hundreds of years to decay, and it can have a profound environmental impact. The route to the landfill is often quite long, as plastic bottles are a very common form of litter around the world, requiring volunteers or government agencies to collect such bottles and bring them to a facility for recycling or other forms of disposal. As plastic bottles decay, they take up precious landfill space, and some leach harmful chemicals into the ground, potentially polluting the soil and water.
Because landfills are so tightly packed, some scientists are concerned that the rate of decay in landfills could be even slower than previously surmised, as the conditions are not optimal for breakdown. Landfills in general pose a serious problem in many parts of the world, as they contain a broad mixture of items which could potentially be recycled, including precious metals, along with potentially dangerous and toxic products. Plastic bottles take up an alarming amount of landfill space, especially when one considers that they shouldn't be in landfills at all. www.wisegeek.com/what-is-the-life-cycle-of-a-plastic-bottle.htm