Three bags full

Spotted this as I walked through town: can you guess what it is?

Since the withdrawal of council maintenance our public flowerbeds and grassy areas are looked after by a community "Greening Group" of volunteers who plant, weed and maintain them at regular intervals. (I've helped a few times but not enough.) Here they used sheep's wool as a mulch to suppress weeds. It looks a bit odd as it's been invaded by a growth of algae but it seems to do the job. It's also a sustainable way to make use of the once-profitable, now almost worthless, by-product of sheep farming.

More about woolly compost here.