I wouldn't use any perennial weeds in a home compost bin - that's asking for trouble. Annual ones are fine Do you not have any plants? Foliage or stems from any perennial that gets cut/dies back, or any annuals, and any veg waste from the kitchen can go in, and those would be greens. My bin is largely made up those, along with grass clippings, apart from those after a weed and feed product have been used. Need to wait around 4 - 6 weeks before adding those. Any ornamental grass that gets divided in spring/summer gets the leaves chopped up first - phormiums and similar. I'm not sure why you'd think sawdust was a green part - that would be considered as a brown, as would things like cardboard, anything twiggy chopped up, shavings from pet waste etc.