I would recommend you compost the grinding. It contains lots of dirt and the inside of the tree. Pine Bark mulch comes from the bark of the tree and doesn't break down too quickly, performing as a mulch should. The grinding will deplete the area of nitrogen, generate excess heat in the summer, go fungal if you get it to thick and crust over and prevent water from penetrating and watering your plants. Pile it up and add a little nitrogen and it will make great compost in about 6 months or less, but don't use it as mulch.
Ed

Thanks Ed. I appreciate the information.