Ranger stations have outhouses (the solar ones don't work well, though Yosemite still uses them, I think).
Yes, Yosemite does use solar toilets very successfully on the high impact trail to Little Yosemite Valley. They work great and are serviced using mule trains to haul out the dried and composted waste on a weekly basis. They are much better than the typical outhouse toilet at a campground.
I agree with you there are old toilets at alpine elevations that have not worked very well, but that doesn't mean they can't. Rocky Mtn NP has been using solar toilets very successfully for 29yrs on Long's at Peak 12,000+ ft with about the same number of hikers as Mt Whitney. They refined the design and they made a commitment to maintenance - which is NOT done by Rangers.
Just wanted to make the point that solar toilets CAN work just fine. Interestingly, RMNP uses llamas to service them on Long's Pk. Now back to Trigger and Seabiscuit.
