Sustainable Alternative to Vermiculite
I love the square foot garden model, but I don't like the fact that it uses vermiculite. Vermiculite, while technically organic and non toxic, is a finite resource. It's a byproduct of mining shale and most of it comes from the same era that mos of our crude oil comes from. Like oil, it's running out at an alarming rate, and I'd rather find a local renewable alternative sooner than later.
I've heard that Texas greensand and Volcanic sand are good alternatives, but both of these are difficult to come by near Seattle. Any suggestions for an alternative in that region?