Sand mining is causing environmental degradation around the world, to river beds, agricultural lands, etc. Taking that out of the equation could be a net benefit. Especially if it's at least as permanent as glass.
But, for extending beaches and most other uses you want textured sand that clumps together. As such people don’t mine river beds for large scale glassmaking as that sand is more valuable.
But what's the impact of cutting down trees + mining for some fraction of petroleum vs mining for glass? I would guess that it requires a rigorous and impartial analysis of the environmental impact.
Recycling could be difficult (once again, I don't have the domain knowledge), but that's only an issue if it needs replacing.
> However, while window glass may not be recycled easily, there are many options for keeping it out of the landfill. For example, it can be melted and re-manufactured into fiberglass, incorporated into asphalt, and even combined into reflective yellow and white road paints. Broken glass can be combined with concrete to create terrazzo flooring and countertops. Some companies even use old glass for landscaping materials and other decorative applications.
...but that's nowhere near a recycled window.
The trick to this is designing crushers which work mostly by grinding rocks against rocks, not rocks against metal. Wear is much reduced.