I get cheap wood chips from the local septic guy. They are things like chipped roots: not your typical pretty yellow landscaping wood chips, hence the low price. But they work great for soaking up the mud and poo. When things start to get muddy or stinky, I drop a couple wheelbarrows full of chips. Don't even have to rake them, the birds will spread them for you.Twice a year, I'll go in and rake them up and add them to the compost. I have great compost.