1. Greywater

... may be considered "dark grey" or blackwater.   In recent years concerns over dwindling reserves of groundwater and overloaded or costly sewage treatment plants has generated much interest in the reuse ...

2. Composting Toilets

... even if a composting toilet is approved. But reputable manufacturers of composting toilets usually help their customers deal with regulatory concerns. Properly designed and sized in relation to use, composting ...

3. Low-flush toilet

... United States in the 1990s with water conservation concerns. ...

4. Sustainability

... of current sustainability discussion track back to the Romantics of the 1800s as well as some Enlightenment political economists of that era. Concerns over population were expressed by Thomas Malthus (see ...