This one stumped me.

[chads]

I cut a large cottonwood (38")down this spring and got a call back on it today.
The stump is seaping and smelling foul.
There looks to be a tan fungus/slimey thing on top.
Now I am trying to figure out how to kill the roots or whatever is causing the smell.
First instinct is to throw soil/lime on top or grind the stump but wonder if it will continue to emit fluid etc.
Chad

 

[Toxic2]

If it were me i would grind it and dump some chemicals or a bag of road salt on it and bury it best i could..

 

[Oldman47]

Make a fresh cut on the stump and apply stump killer like Tordon RTU.

 

[066blaster]

I've ground some cottonwoods that smell like their fermenting. Probably some pockets holding water in it.

 

[Wood Doctor]

Cottonwoods drink loads of water while growing and the roots will drink for weeks after the tree is cut down. When first cut, I have seen them collect water on the top of the stump and actually overflow water over the sides of the stump. Initially the water could be fresh enough to drink, but in time it turns stale and will give off odor. Usually it all ends in a month or so.

 

[bitzer]

When the sap is running in spring pretty much every stump will grow some funky colors.