I've washed body and hair with a baking soda solution, with great results. It's the easiest thing to wash with when living in a van because it cuts body oils, deodorizes, and you don't have to rinse your skin. Mix about two teaspoons to a tablespoon in a quart or two of warm water. If you find a powdery coating on your dry skin, use less next time.
I also used the same baking soda mix on my hair, but I did rinse it with water with a spoonful of vinegar in it; for some reason, it seemed to make the tangles in long hair easy to remove. You can wash your hair sitting in the door of your van with a plastic dishpan between your feet (or with your feet in it - wash them last). Just lean forward and slowly pour the warm soda/water mix through your hair while massaging it; combing it through seems to help, too. Rinse w/plain water or water with a spoonful of vinegar in it.
There is a difference between soap and detergent: soaps are produced from natural products (fats & oils with various salts added), and detergents are made from synthetic ingredients.
Richard, every word of that article may be true, but coming from a site called BadAssU doesn't exactly make a person worry very much about it; some people ride a wide variety of hobby horses, and change them frequently.