It seems like you could invent a walnut-shooting gun and then open a walnut shooting range. You make the guns with the right amount of power to break the shells without ruining the nut.
People come and pay you money to shoot walnuts at targets, and at the end of the day you go to the targets and pick up the shelled walnuts. Maybe you even offer a contract for someone else to pick them up and sell them, and you make money on both ends.
My ancestors fought cave bears so I could make this post.