Thanks for sharing more details on the chemical makeup of plastics @andreajane! It's interesting to gather more insight into the origins of the household goods we take for granted.

To others perusing this post, if you're hungry for more information on these types of houses, I'd recommend checking out...

For a general overview: https://en.wikipedia.org/wiki/Earthship
Videos by Earthship Biotecture: https://www.youtube.com/user/earthship

I tried making one of these houses myself using recycled tires as the base, and never got around to completing it with bottle-bricks. I'm sure kids in schools would enjoy seeing how to build their own house using much more accessible and earth-friendly materials -- so thank you @andreajane for fostering that creativity in them!