The staff ate it later

I would go with "Care has been taken to minimize food waste." or some paraphrasing of it.

Even if that would be more accurate - if your audience is accustomed to seeing "the staff ate it later", and that is only a feel-good checkbox for them (vs. a metric that anyone cares about optimizing), then it is better to go with what your audience is accustomed to. Otherwise, you're running off into the weeds.