I read a few forums where people would use topsoil as an alternative to pine shavings. They said literally only had to remove the top layer of soil once a month. It's a lot cheaper than pine or recycled newspaper. However, they have to bake it in the oven prior to using it. I thought since mice in the wild live in dirt, couldn't you use topsoil out of the bag? I can't imagine baking or freezing topsoil.