Tracy, my grandma grew English walnut tree. The shells were so thing, I was able to put two in my hands and press one against the other to crack.
But cleaning them from the green skin was not an easy task. Since I was impatient, my hands would get all black and my mom would be not pleased. School was starting at about the same time. Good old times...
sorry for changing topic again
On the topic, I know that even paper can be used to build the soil, even grow mushrooms. Newspapers have to much ink, magazines as well. Boxes picked from local stores can be used for that. Maybe...