"tomba wrote:
I have had four pine trees removed, but because of their location the
tree people cannot use the grinder to get rid of the stumps. I would
like to remove them without using harmful chemicals.

Soft woods like pine don't take too many years to rot away all on
their own with no human intervention. I cut many large spruce trees
on my property and the stumps were reduced to a hole in teh ground
filled with rotting pulp within five years... but these are along a
heavily shaded wooded path where it's always quite moist... would take
twice, maybe three times as long in a sunny dry location. The spruce
I cut were between 18"-24" diameter, you'd be amazed at how large a
hole they leave, takes like two yards of fill.

There are various brands of wood digesting enzymes that will greatly
speed up tree stump decay that are no more hazardous than the cheese
in your fridge. But, if a tree stump is in close proximity to your
residence, especially if at the foundation, it can easily attract wood
eating insects (termites) to your home, then it's best to either dig
it out or if you are unable then hire someone who can, do not leave
them to rot.