What sort of Sustainability Requirements are people writing? Curious? Go see what people have written.
What about you? How do you include envirnmental issues into your project?
Greening your project is actually harer that you supose it will be on first reflection. There is a cost/benefit trade-off here. Spend money now to save later.
One thing you should do is check your company's environmental and CSR policies to see how you can roll in sustainable requirements as development constraints.
If you want to take the conversation further, please do here, there and other places. The more the better. This is a serious and ugent issue.