Check out Franmar, they have a whole line of environmentally friendly cleaners.
Franmar Chemical - Environmentally Friendly Cleaners and Removers
Franmar Chemical - Environmentally Friendly Cleaners and Removers
I suspect that only a small percentage of the billions of T-shirts in landfills are there because they wore out. Most are there because they went out of date, out of fashion, or were just never meant to be worn more than a couple of times in the first place.The best thing for the environment, is to produce shirts which can be washed 100 time or more.