I can't imagine they are making their product on an order-by-order basis. Nor would they be buying supplies for their product that way, and selling back supplies is not a frictionless process. Of course there is a stockpile.
It's plastic. They sell it in the form of "hurdles" (http://en.wikipedia.org/wiki/Plastic_particle_water_pollutio...), small plastic particles, which are mostly standard sizes. These are then processed into their final form as required by simple machinery. Typically these are fed into an injection molding machine to make plastic parts, but could be used to produce plastic bags or sheet plastic for thermoforming.
Unless they're adding something to the plastic, or coating it in something, they could absolutely just ship it back as smaller than usual nurdles, or make use of it for something else in their manufacturing process, like making bottles or caps.
In any case, do you really think they have a two year supply of this stuff? That'd be crazy.
I find it very plausible that they have a two-year supply of particular products, that can easily happen if demand does not meet expectations, or if they planned limited campaigns of particular products.
These micro particles of plastic are used by the train load which is why it's horrifying they're still being used. Where would you keep a two year supply if you needed that much of this sort of material? A plant the size of Wyoming? Secondly, they do not have warehouses of toothpaste sitting around. It's perishable.
This isn't the 1920s. Most major companies run on much leaner inventory, and it's not uncommon to turn over your entire warehouse several times a month.
