David de Rothschild is talking trash, lots and lots of trash.

“There were 25 billion Styrofoam cups used last year. How do you even get your head around what 25 billion Styrofoam cups looks like?” he said. “Eighty-odd percent of what’s purchased by Americans is thrown out within six months.”

On this day, though, the British banking heir is focused on some very particular refuse as he skims along the San Francisco Bay in a catamaran called Plastiki: The 12,000 or so recycled soda bottles lashed together to build his clunky vessel, and the growing heap of plastic fragments called the Eastern Garbage Patch floating in the Pacific.

If all goes well -- so far, it’s been a little hit and miss -- De Rothschild hopes to set sail aboard Plastiki in March, tour the garbage patch and end up in Australia, while blogging about the evils of plastic and a consumer society.

He also wants to highlight Plastiki’s innovations, like the glue made of cashew hulls and sugar, which he said “could go to market today and take epoxies -- horrible, noxious stuff -- off the shelf straightaway.”

En route from Sausalito to Sydney, De Rothschild will navigate two well-trod traditions -- quirky British explorer and modern eco-celebrity -- in a quest that smacks of equal parts Sir Richard Francis Burton and Ed Begley Jr. The first conquered uncharted territory; the second powered his toaster with electricity generated by pedaling a stationary bike.

De Rothschild, 31, has been lauded as an eco-adventurer, envied as a “billionaire eco-warrior” and derided as a dilettante “eco-toff” -- British slang for a rich boy with a clean, green conscience.

He prefers the term “environmental storyteller” and said the “idea of the celebrity eco thing makes me want to puke. . . . It belittles the severity of the issues that we’ve got to tackle. Unfortunately, we’re in a society that loves labels and loves celebrities.”

This from a man whose Sundance Channel series, “Eco Trip: The Real Cost of Living,” was promoted online with video of a lanky De Rothschild, wetsuit half off, voice-over describing the bearded Brit as “the hottest thing since global warming.”

To be fair, though, sailing a boat made of used bottles across the Pacific Ocean is a lot more challenging than driving a Prius to the Academy Awards.

A onetime hyperactive child turned top-ranked horse jumper, De Rothschild stayed away from the family’s storied banking business. He got a degree in naturopathic medicine and bought an 1,100-acre farm in New Zealand, where he still grows organic medicinal herbs.

In 2004, he signed on to an expedition to traverse Antarctica. Facing whiteout conditions, the group spent the first two weeks in small tents waiting for the weather to turn. To pass the time, De Rothschild dared his trek-mates to do stunts.

“Snorting energy drinks up our noses, putting your tongue on the front of the snow machine, bare metal at minus 30 degrees,” recalled expedition leader Patrick Woodhead, who likens De Rothschild to Tigger on Ecstasy. “It’s a miracle we didn’t injure ourselves before starting. . . . David is the most enthusiastic person I know.”

Before leaving for Antarctica, De Rothschild took out an ad in a New Zealand teaching publication urging students to learn about the frosty region.

It showed teachers how to follow the trek, and “let kids plan their own expeditions in their classrooms,” De Rothschild recalled. When he returned home he was “bombarded by messages from teachers.”

Six months later, he launched Adventure Ecology, an organization that blends treks and technology to teach schoolchildren about the environment.

Then he set off to cross the North Pole with skis and sled dogs and chronicle the trip online. But melting ice made it impossible for the team to finish its journey.

“There I was in my tent wearing merino long johns, cooking my dinner and sweating away,” he said, recalling an April night near the North Pole. “It doesn’t take a scientist to realize that something’s amiss.”

The trip was aborted after 100 days, he said, but the Adventure Ecology website got more than a million hits.

While researching his next trek, De Rothschild came across an article by Charles Moore, a Long Beach marine researcher who had sailed through a vast, plastic-filled gyre between Hawaii and the U.S. mainland.

De Rothschild had found his next cause. His first thought was to sail to the Eastern Garbage Patch with a crew of artists, who would create an installation to highlight how plastic is poisoning the oceans.

But the environmental storyteller had a problem. “Unless an artist falls overboard or there’s a fight . . . where’s the narrative arc?” he was asked by Jeff Skoll, whose Participant Productions released “An Inconvenient Truth.”

So De Rothschild started thinking about Kon-Tiki, the storied raft that explorer Thor Heyerdahl built out of wood, reeds and bamboo and piloted across the Pacific in 1947.

Romance? Check. Adventure? Check. Timing? Check. Kon-Tiki had it all, and De Rothschild wanted some of the same for his own project. The idea for Plastiki was born. But first, it had to be built.

“The boat had to carry six people across the Pacific,” recounted naval architect Andrew Dovell, whom De Rothschild commissioned to build Plastiki. “The vessel had to derive its primary flotation from two-liter drink bottles. They had to be visible.”

Dovell decided Plastiki would be strongest and most buoyant if it were built as a catamaran with a framework of plantation-grown plywood. But De Rothschild had other ideas: Plastiki should live up to its name and be made entirely of plastic -- recycled or recyclable.

The team’s first stab at using recycled plastic panels was a failure. Thus began 18 months of research and development on San Francisco’s rickety Pier 31.

Plastiki missed scheduled launches in December 2008, and April and December 2009. A hoped-for launch this month has been delayed until at least March.

The team, though, has perfected the self-reinforced polyethylene terephthalate, which forms the catamaran’s superstructure. The panels are strong. Recyclable. And untested as a boat-building material.

On this cloudy afternoon the wind rises, but Plastiki’s ride is smooth and quiet. What would happen, De Rothschild is asked, if the boat hit a storm strong enough to pop the soda bottles out of its twin hulls?

“Well,” he laughed, “I put earplugs in. I put my eye blinds on. I listen to Led Zeppelin.”

maria.laganga@ latimes.com