Sustainability is more often about the process, than it is about achieving specific goals and then moving on to something different. There is always room for improvement, and opportunity to become more sustainable.
In order to get the desired amount and quality of milk, cows need healthy pastures to graze on.
Here is a short description of what we do to improve the benefit that farmers derive from our research. There is an example used of a course attended in order to broaden our knowledge.
As to whether effluent is a waste or a benefit, depends entirely on how you, the farmer, use it.