Urine may be sterile when it leaves, but it plays a huge part in the nitrogen cycle, breaking down into ammonia and its by products and is a seriously good plant fertiliser - commercially made nitrogen fertilisers take the nitrogen directly from the air and are massively energy intensive to produce. As far as the solids go, grazing animals don't produce the best dung, just a lot of it - think of chicken or pig manure, both famous for their value in agriculture/horticulture and both from omnivores (by nature at least). When you use "farmyard manure" in your garden, the bigger part of the value of it is in the urine that has soaked into the straw and broken it down. You can turn principle this to your advantage by peeing in your compost heap, which will help it heat up to destroy pathogens and speed up the composting process.
Some treated human waste does still make it to the land, though without looking it up, I'd be guessing if I said how much.
