You cannot get any more environmentally friendly than a waterless composting toilet. Most conventional toilet systems such as septic tanks were not developed with the environment in mind, so they are often a cause of unnecessary pollution. Composting is nature's method of renewing itself by reducing and recycling waste into natural compost, while using little or no water in the process.
Download this brochure about the Envirolet Composting Toilet to learn how these systems work, benefits of selecting a composting toilet, and features and specifications of different models. Topics discussed include:

Santerra Green Composting Toilets
Bathroom Remodeling: Strategies For Energy Efficiency
Performance Toilets
TOTO on Sustainability
Hydrotect from TOTO - Makes Surfaces Easier to Clean