I had a guy stop one year when I was shoveling them up and he asked if he could have them. I was more than happy to tell him yes and go for it.
Him and his wife came out and picked them all up a few diff times. He said he dumps them in his gravel driveway and drives over them all winter. When the meat is totally off the nut, they pick them up and crack the nuts open for the walnut.
He only did it for one season....never heard from him after that.