Freezing is suspect for effectiveness many insect eggs can resist freezing. Some bacteria and virus as well. Baking microwave is an effective sterilizer, I just don't know what would happen with wood??? I have a friend whom uses a BBQ to heat treat drift wood he has deep sided baking sheet filled with water and a second on top like a flat double boiler so it doesn't burn. I know one other whom uses boiling water over substrate and then dries in out after.