In many ways the career trajectory of US green entrepreneur Adam Werbach mirrors the transition that environmental issues have made in the last five years from being almost the sole preserve of lobby groups to one of the dominant issues in the world's boardrooms.

Having become the youngest ever president of the Sierra Club at the age of 23 and helped drive the average age of the group's members down from 47 to 37, Werbach moved in 1998 to found Act Now – a green business consultancy that would infuriate many of his environmentalist peers by, in Werbach's own words "selling out" and working with corporate giants such as Wal-Mart.

Werbach's journey into the corporate mainstream was then completed last month when Act Now was acquired by Saatchi & Saatchi and he was appointed head of the advertising giant's new sustainability division, Saatchi & Saatchi S.

BusinessGreen.com caught up with him on a recent visit to London to ask what the journey had been like and what the new Saatchi & Saatchi S would offer its customers.

BusinessGreen.com: What made you cross the fence from environmental campaigner to entrepreneur?
In the end I was enormously frustrated by the distractions [that accompanied the environmental movement]. For example, at the Sierra Club we had this eternal debate about whether population control and immigration were an environmental issue. I thought that was a silly argument and eventually I left to form Act Now with the idea of using the media as a tool to reach the public with environmental issues.

You are on record as being pretty critical of the environmental movement. Where do you think it has failed?
In 2004 I stood up and gave a speech at the Commonwealth Club in the US saying that environmentalism was dead. My experience was that this movement that I loved had failed in its most basic responsibility, which was to have a realistic plan to solve the problem we were faced with.

What caused that failure?
If you look back, it succeeded in the 1970s in the US in particular, by creating a regulatory framework to help fix the dirty skies and so on. We had the Clean Air Act, the Clean Water Act, the Endangered Species Act and all that good stuff happened in a matter of a few years. Since then Europe has skyrocketed ahead and in the 90s the US basically slowed down. While the problems seemed to get worse and worse each year the mechanisms to solve them became thoroughly enfeebled. By the mid 90s there was the EU, which was quite a strong body for addressing these environmental problems, but in the US there was a strong belief in limited government and local control. The US had gone from a position from being a leader to a position where it was not just no longer a leader but totally structurally unable to be a leader. I felt there was a culpability of the environmental movement in that shift because it never had a serious plan to engage the public to change it.

So you effectively left the environmental movement?
I essentially quit. I got a bunch of calls from people saying they wouldn't work with me anymore, then I got this one call from Wal-Mart that I first thought was a joke. I was actually pretty blown away by what they were aiming to do. They basically set three goals: purchase 100 per cent renewable energy, produce zero waste, and aim to green the products they sell. The conventional wisdom was that those targets couldn't be met, but they asked me to help implement it. It took a long time to say yes, but we decided to engage because it seemed to be the best pathway available to tackle many environmental problems. Our feeling is that if we are serious about tackling climate change and other issues we have to work to the scale of the problems we face. And working with the biggest corporation on the planet is one of the best ways of doing that.

A lot of green consultancies have emerged in the past few years. What services does Saatchi & Saatchi S offer?
From tip-to-tail that means we work at the product and process level looking at product and process innovation and we have deep capabilities to help business make sure that at their core they are sustainable. Then we look at really engaging an entire company in sustainability. This is something that cannot just be led from the top it needs to be led from the bottom too. So with Wal-Mart we trained 1.7m people to care about sustainability. We see that companies that are serious about it have everybody in the company serious about it – it's not just the head of CSR that is involved.

Some might argue that runs counter to the conventional view that board members and senior management are key to the success of any green initiative.
Of course, the board needs to be behind it and we will not work with a company unless the CEO is involved. The board doesn't really work with the employees and the best proof of whether a company is sustainable is if you walk into a store or a factory and talk to the employees and find that sustainability is important to them. When people say this matters to me because I want to make sure my company is competitive in the 21st Century or I want to conserve the water in my community that is when you know you are making progress. If everyone in the company can articulate those opinions that is the best advert for any company. If we stopped working with Wal-Mart right now, if the CEO and board left Wal-Mart right now, it would still be headed inexorably towards becoming a sustainable company because the people who work there care about this.

How do you get employees involved? Not everyone is going to care about the environment.
The first thing you do is you make it voluntary. The only thing I believe is that people should be rewarded [for reaching environmental targets], but personal involvement should be voluntary. We go for an old school grass roots organising model, which is defined by meeting people where they are at, finding out what their needs are and finding out how that relates to sustainability.

How do you convince people within a company that there is a business case for green initiatives?
You have to be very honest about it. You hear people say the green consumer opportunity is 40 per cent of the marketplace. In the US and Britain it is 10 to 12 per cent tops so don't inflate the numbers. But in all honesty you really don't have to make the case anymore, because people are seeing it. They are seeing the risks and they are seeing the emerging opportunity. You will always find some people who want to argue, but the vast majority can see what is happening and can see the business case. I believe every business should be a green business, and the reason why is not because it is good for the soul or because they have to, but because it is good for your top line revenue and good for your bottom line revenue.

Given the environment is now emerging as a mainstream issue what is the biggest problem we now face?
The scale issue is critical. Wal-Mart is the largest corporation ever created on the planet, but it wasn't big enough, it isn't big enough. The number of problems we tried to solve on their behalf where we found the solution had to be industry-wide and global was amazing. Part of the thinking behind the Saatchi deal is that it can provide us with a way to deal with what I think is the most important consumer products company in the world, in Procter & Gamble, and the most important car company, in Toyota.

What would be your response to the argument that a lot of firms are simply applying a layer of greenwash to their activities and not making the required changes first.
The green marketing and messaging is really at the end of the pipe. With our clients we do a lot of work before we get to there and once they are there Saatchi & Saatchi can provide that messaging expertise. I’d agree we're all greenwashers and there is no such thing as a green company [because] it is always a journey and you are always trying to get better. But greenwashing in the sense you are talking about it is when you are communicating out of scale with what you are doing. If you look at Wal-Mart it spends over $1bn a year on advertising and spends less than $1m a year on sustainability messaging. That would be the main message, communicate at the scale you are working.