Hi Kelly, looks like a great outhouse. I would suggest not using anything but carbon based material for cover. No sand or ashes as they will interfere or stop the break down of material. Any all wood sawdust, leaves, grass, old compost or anything that used to be growing and is now fine enough to produce a bio barrier. The better your composting works the less work you have to do in the long term.
Life is too short or my list is too long, not sure which.
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