And how would such chair compare to your standard injection moulded chair from mostly pristine materials? From whole lifecycle perspective.

Typically it is much heavier. Like 5x the weight.

For example it might look like this: https://www.recycledfurniture.co.uk/Benches-and-Seating/Park...

And obviously a heavier product has itself a larger environmental impact when it finally comes to be disposed of - weight is a rough proxy for environmental impact.