Michigan seems to be more strict than some other states about what kinds of businesses can remain open during this coronavirus. According to Governor Whitnmer "I would encourage any business that is not sure if they're life-sustaining, to probably assume that they are not." Based on that statement, I'd assume that building wood processors would not be considered "essential."
You can read about Governor Whitmer's essential order here: Whitmer clarifies essential order: 'if businesses are not sure if they're life-sustaining, assume they are not'