Wow, that's bad!
Also the tree looks like it's too deep or too much mulch near the trunk. You should see the flare of the trunk a bit better.
I think that wax is dripping off ... get rid of it.
You know, if that were a human leg and that much skin was ripped off exposing the muscles etc the surgeons would take a graft or use some generic lab skin that might work.
The thing with trees that's really different to people is that their vascular system is just under the bark ... hence ring bark a tree it dies.
Now over half the dia of the tree is missing it's vascular system. This could mean that that side of the tree slowly dies ... roots too.
Now this is a controversial move. Like with the skin graft you could take a section of bark from elsewhere and graft it to that injured section. If it takes it feeds the tree more on that side and helps grow and cover over the wound. However you get a new wound where you took if from. So you'd take it from the good and most healthy side. Say a 1" wide long enough piece to make a vertical strap. You cut the ends at an angle and tuck it under a mirror cut on the good bark above and below the wound. Small tacks ... tack it in place. Then also have to nurse the new injury. This process is called
bridge grafting. You do this in spring or growing season, make sure you are clear on what has to be done.
Here's some similar links to help you.
http://www.hort.uconn.edu/Ipm/homegrnd/htms/28graft.htm http://www.omafra.gov.on.ca/english/...03.htm#figure1 http://www.extension.umn.edu/distrib...s/DG0532c.html