If you are unfamiliar with the process of removing a stump this section is for you. If you are familiar with the process feel free to skip this section.
Most stump grinding machines have a rotating wheel with carbide teeth on it. The wheel swings back and forth as well as moving up and down. Each pass cuts off a little of the stump moving lower each time. Eventually the cutting head moves below ground and takes out the roots. You move forward and repeat until the entire stump has been removed. The stump is reduced to a mulch like product.
Just like cars are different, stump grinding machines are different. They come in a variety of sizes with different engines and speeds. Smaller machines make smaller passes and take longer to get the job done. Larger machines get the job done faster.
The process can be disruptive to the work area and can leave quite a mess. Stumps under 24 inches in diameter generally don't leave a significant amount of debris ( mulch ). Over 24" the mulch piles become large and as the diameter of the stump increases the amount of mulch goes up at a rate of about 4 to 1 when compared to the diameter. This is important if you plan on cleaning up the debris on your own. Also consider that stump mulch has a significant amount of dirt and rocks mixed in. There are not a lot of uses for stump mulch, its not really suitable as decorative mulch and not much grows in it. When deciding if the mulch is something you want to deal with take into account where and how you plan to dispose of it.
It's common for customers to be surprised by the amount of mulch from a large stump. The photo above was the mulch generated from a 50 inch Sugar Maple stump, about 4 yards worth of material.