[Editor's Note: This is the final segment of a three-part article on how to pinpoint the business case for sustainability by David Bent of Forum for the Future. Here are Part 1 and Part 2.]

Good environmental management has saved telecom group BT more than $700 million. It used clear-eyed analysis and fundamental financial tools to identify the business case for sustainability. Here are the steps you can apply yourself.

Finding the business case is the "holy grail" of sustainability professionals, a goal which sometimes seems impossibly hard, and yet there are actually many different business cases for sustainability projects, change programs and initiatives.

In previous posts I gave "Six Lessons on Finding the Business Case for Sustainability Initiatives" and "Four Tips on Getting Buy-In from Finance." This final post goes into the technical part -- seven steps to investigate the business case.

I'll illustrate with the work Forum for the Future did with BT, which helped the telecoms group save $720 million (£442 million) in operating costs over five years:

1. Identify what you're investigating and why.

Obvious, but you'll be surprised how poorly people define boundaries. Are you looking at the sustainability drivers for the whole organization or only a particular project or initiative? Are you looking at the worth of an entire change program, or do you want to add sustainability-related criteria into a decision-making process like capital expenditure budgeting? Make sure you know your scope.

You should also be clear why you are investigating. How will you use the results? What is the change you're trying to stimulate?

BT was interested in identifying the financial benefits of good environmental practice for reporting and marketing. Crucially, they narrowed that down further to some particulars: transport, energy and teleconference working practices.

2. Prioritize value drivers.

Shareholder value -- the value of the company to its owners -- is driven by certain factors: turnover growth; margin growth; reduced capital expenditure; risk reduction; duration of competitive advantage; reduced tax rate and reduced cost of capital. Identify which of these is key to your investigation. (Different writers have slightly different lists. This is from "In Search of Shareholder Value: Managing the Drivers of Performance").

For BT the value driver was clear: margin growth.

3. Identify the relevant business cases.

Each value driver may have a number of different possible business cases -- we've compiled a list of 17 pathways from sustainability to shareholder value (see here). Do get in touch if we've missed out any.