Mix it into compost so that the ratio is 30% droppings or less. This can be used as landscaping fertilizer, but even then it’s not recommended to use for food production.
I’m unsure. I know there happens to be a correlation between the species that are (mostly) herbivorous, and their dung being able to be used with food production. I don’t know if our gut biome would prevent the use of purely vegan poo. I prefer the sewer as a solution, or a latrine.