I am strongly in favour of sustainable knitting. My way of addressing this issues is twofold : first, what went into the process of creating this fibre (how much water, toxic products, etc.), secondly, what becomes of the knitted items. Is it able to decompose speedily or not. I know many knitters are keen on their petro-chemical fibers or viscose, bamboo, etc. I give input to make these knitted items to last as long as possible (aka they remain wearable items and don’t speedily become waste that is very hard to recycle).