Composting horse manure?
I've got a friend who has lots of Horse manure mixed in with cedar wood chips. It's aged about 3-4 years but still has the horse "apples" more or less intact. How can I compost it further, to actually make it usable in my garden? And do I need to worry about pathogens? Thanks.
It doesn't sound like it has "aged" enough to be garden-ready. I'd recommend properly composting it for at least one season. By properly composting I mean a hot compost heap. This will kill weed seeds and any parasitic eggs. It will also reduce the likelihood that the manure will burn your plants. Read here:
As for pathogens, manures from herbivores are generally safe (after composting). Trouble arises when using manure from carnivores (cats) and omnivores (dogs, humans).