These CEOs bet billions on seemingly unrealistic sustainability projects–and won. I asked them how

Sustainability has emerged as the defining issue of our time. What was until relatively recently a niche issue has suddenly become everyone’s most pressing priority.

But how can companies turn their goodwill into action? How do we go from pledge to practice?

As a former CEO myself, I know only too well how daunting that challenge can be. There are so many unanswered questions and so little time to seek answers.

One of the great privileges of my current job is having direct access to some of the world’s greatest CEOs—those who have the vision, courage, and grit to make huge strides toward sustainability.

They prove that it’s possible to do good in the world and grow your business at the same time. We’ve spent hundreds of thousands of hours trying to decode their DNA and understand exactly why they succeed where others fail.

The answers can often be counterintuitive. For example, you might assume that being a perfectionist is a good thing. But when it comes to sustainability, being a “100 percenter” can hold you back.

The CEOs and companies who are making the biggest strides are the ones setting big, hairy, audacious goals before they’ve ironed out all the details.

Here are three examples.

The Tesla of the seas

Imagine the chutzpah it takes to invest $15 million into building the world’s first driverless, crewless, zero-emissions container ship—when you don’t even know if such a ship would ever be allowed to set sail or drop anchor under maritime law.

Yet that’s exactly what global fertilizer giant Yara International’s CEO, Svein Tore Holsether, did. Taking inspiration from Elon Musk, Svein created a “Tesla of the seas” despite many unknowns: Would it cope with heavy traffic in large ports? Might it collide with whales, seals, or even kayakers? Without a crew on board, how do you manage faults and repairs? Can a computer ever make better decisions than a human Captain?

Despite all these questions, Svein pushed ahead. Why? Because he knew that by the time he had all the answers, it would be too late to act. As he told me, “You have to be at the forefront of things and demonstrate what can be done. I’d rather be fired for taking too much of a risk and making a mistake than not acting soon enough. You need to build first, talk later.”

Of course, Svein’s leap of faith wasn’t a stab in the dark. It was an educated and calculated risk, based on the best available science. But while another CEO might have waited until they had all the answers, Svein dared to steer into the unknown.

Thanks to his bold and decisive action, the Yara Birkeland is now a reality and undergoing two years of testing. Once up and running, it has the potential to save a staggering 40,000 truck trips and 1,000 tons of CO2 a year.

Not so insurmountable

If investing $15 million in a ship that might never be allowed to set sail sounds audacious, then how about spending $2 billion on a fleet of clean containerships when you don’t know where you’ll get enough green fuel to power them?

Meet Søren Skou, CEO of the global shipping giant Maersk. When Søren announced his plans, it was a massive risk. Green containerships cost about 15% more to build. And green fuel costs more than double, assuming you can even find enough to power your ships.

But again, Søren’s big gamble was an educated one. He saw which way the winds of sustainability were blowing. He knew that somewhere out there in this big wide world, where sustainability is everyone’s number one mission, there would be a solution.

He was right. In Søren’s words, “All those problems at the start that we thought were so huge we had no idea how to overcome turned out not to be so insurmountable.”

As it transpired, Yara (yes, the very same) and Ørsted came forward with the answers. Søren’s timing also proved to be prescient: The likes of Unilever, Amazon, and Ikea (some of Maersk’s biggest customers) have since announced plans to only use zero-carbon logistics partners by 2040.

“Our ambition to have a carbon-neutral fleet by 2050 was a moonshot when we announced it in 2018,” Søren said. “Today we see it as a challenging, yet achievable target to reach.”

The art of doubling down

Not long after becoming CEO of Adidas, Kasper Rorsted decided to launch a small and experimental line of shoes made from recycled ocean plastic. It was called Parley, named after the environmental nonprofit Parley for the Oceans, which co-developed it.

Once again, there were plenty of unanswered questions. Would they be able to find enough recycled ocean plastic to scale up? How well would it perform? Kasper and his people spent a lot of time finding the answers. But they became so obsessed with the detail, that they lost sight of the marketing.

Adidas had created the perfect sneaker, but their consumer knew nothing about it. His team got so deeply into the weeds of the design and execution that it eclipsed the marketing of the product. They lost passion for the big picture of what Parley was all about, then failed to communicate its message–that all-important market differentiator of depolluting our oceans from plastic–to the rest of the world.
However, Kasper learned an invaluable lesson–and he was not afraid to turn up the volume on his next target: to make nine out of 10 of Adidas’s products, from running shoes to soccer jerseys, out of reusable materials to end plastic waste by 2025.

He intentionally held himself externally accountable because “eventually the world will come and chase you on it.” Many within Adidas balked. They were afraid of not meeting this goal, which was understandable, but Kasper believed it was his role as leader to push his team to set all their reservations aside, go hard, and rise to this public declaration.

As he said: “Make it simple, make it public, and drive the behavior.”

This article originally appeared in Fortune.