The only truly environment friendly car wash would have to be a plant based solution. While such a wash works exceptionally well and the car even stays cleaner longer it does not produce much in the way of suds. Therin lies the problem, we are all so programmed to think that the more suds the better that a non or low sudsing soap will make us think it isn't working.
How do I know this? I tried for a while to market this exact product, it had to be the toughest sell I ever had, nobody re-ordered because they could not get used to the low suds. I myself still use it but even though I know the suds mean nothing, I can't get over the lack of suds, it's so ingrained in my mind that I can't shake it, it can be a very disconcerting experience
The only option is to add a sudsing agent like all car soaps do and this defeats the environmentally safe purpose.