It's late, but let me write some notes in case I do well.

This solution brought to you by omclone.

I made a solution that managed 10 atoms of waste in the output chamber by having 2 triangles of waste and 1 triangle of waste with an extra atom bonded on.  Then I thought, "What if I could manage 3 atoms of waste in the input chamber and have just 3 triangles of waste (for the remaining 9 waste) in the output chamber?"  I was able to make it happen by landing on this input chamber layout, where I can stuff waste on the top or bottom while using the other half.  3 basic triangles of output-chamber waste made 1P waste handling so much easier.

Everything else is optimizations on top of that: bonding two of the triangles into a connected waste chunk, having silver waste to streamline the very first input arm movement, deciding on a build order where the second-to-last atom to be bonded is earth (to aid input chamber waste juggling), and many more micro-optimizations.

What a great puzzle!  I went from "90g is min" to "Oh no, 80g is min, but it's annoying." to "What if I can 3p it?" to "What if I can 2p it?" to "What if I can 1p it?" and kept finding new things to try.