Are you sure? No lumber companies or arborists throwing away
wood chips or wood waste?
I'm just guessing, please don't be offended; Europe is pretty good at getting companies to put all their
chickens in order. Many USA companies just want to throw stuff away, so that waste stream is open which is why it is free. For the mulch, it is free because it is expensive to pay fines for throwing it away and to haul it to the landfill. So a gardener can call a company and ask for their waste stream. The trick is, most people don't know they can just ask. It's that simple.
Now, if one wanted to do "Bomb-Proof-Sheet-Mulching" as Toby Hemenway talked about in his book
Gaia's Garden, here are some ideas on waste streams to communicate with to get the materials:
1) Grocery stores
2) Neighbors
3) Municipal government offices; save government money, whatever wasted you like:
trees, organics, etc
4) Sawmills