PwC presents in an interesting paper an expanded shareholder value framework to accommodate the intangible benefits of sustainability initiatives. The difficulties with quantifying the benefits could be solved with both direct and indirect valuation methods. In this way it is easier to analyze, prioritize and measure the contribution sustainability initiatives make to shareholder value.
Though, the benefits from sustainability initiatives are uncertain, but this is considered an advantage: value is thought of a range, with potential good and bad surprises. Read the paper here.