Years ago when I was rafting the Green and Colorado Rivers, it was standard on the stretches of river controlled by the Park Service or BLM that you peed in the river and pooped in a bag to carry out. Peeing on land in the arid environment means a buildup of ammonia in the soil because it's not very bioactive. Also, the camping areas are fairly limited and frequented in season by lots of river trips. Poop went in a bag in a bucket. Actually, we used an old ammo box, double super duty plastic bags and a toilet seat. Each day, set it up, each morning, wrap it up tight before packing. Not so bad, really. Everyone took a turn, so nobody had to do the job more than once on a 5 day trip.