Activists briefly stormed onstage to protest after Steven Leer, chairman and CEO of Arch Coal, Inc., spoke on “The Vital Role of Clean Coal in Securing our Energy Future” in Science center C last night.

Representatives from a Boston environmental group burst onstage and briefly commandeered a talk given on campus by a coal company executive yesterday evening.

The activists, members of Rising Tide Boston, a self-proclaimed environmental and social justice group, came to the front of the room during the talk’s question and answer period and unfurled a banner stating “clean coal is a dirty lie” while listing grievances with coal as an energy source.

As two of the activists held the banner, another questioned the speaker, CEO of Arch Coal Steven F. Leer, on the viability of coal as a solution to climate change.

When moderator Daniel P. Schrag, an earth and planetary sciences professor and director of Harvard University Center for the Environment, asked the objector his name, the man replied, “coal kills.”

Several audience members responded to this statement with applause.

The interruption concluded when Schrag asked the Rising Tide representatives to leave the stage.

Before the disruption, Leer promoted clean coal technologies, such as Carbon Storage and Sequestration as a means of balancing increasing global demand for electricity with a need to stabilize atmospheric carbon levels.

“I try to deal with facts, I was trained as an engineer. Let’s not let the perfect get in the way of the good.” Leer said.

“If you really want to stabilize carbon dioxide in the atmosphere, we have to develop carbon sequestration tactics.”

He cited coal’s generation of 49% of America’s electricity, the increasing demand in developing countries such as India and China, and the global availability of coal as evidence that it will continue to be an integral energy source.

“We want a reliable, affordable, clean and secure energy source to power economic growth in the 21st century,” Leer said. “The world is running out of energy, and CCS and cap and trade are opportunities to solve some of the world’s energy problems in a cleaner and more efficient way.”

Leer’s goal is that the U.S. and Europe pioneer clean coal and CCS technologies in the U.S. and Europe and then export them to developing countries.

Several audience members, in addition to the Rising Tide activists—who in an interview called the speech a “well-crafted” defense of an “obsolete” technology—were unsatisfied with Leer’s defense of coal.

“Clean coal is like healthy cancer. I don’t believe it exists.” said Andrew Stern, Vice President of Citizen Advocates for Renewable Energy, which installed wind turbines from which Harvard buys energy credits.

However, many audience members said they respected Leer’s pragmatism.

“His basic message was that there is an enormous amount of incredibly cheap coal and people are going to exploit that—it is a fact, a reality,” said William W. Hogan, a global energy policy professor at the Harvard Kennedy School. “The trick, what is absolutely critical, is to find some way to deal with CCS...wishing we didn’t have to address this problem is wishful thinking.”

Schrag said he appreciated Leer’s presence, calling him “the most progressive force in the coal industry,” and said he found the interruption objectionable.

“[The activists] didn’t listen, they didn’t state their names, and it was rude,” he said. “There are lots of diverging views in this series. We must be tolerant of ideas, even those we disagree with.”

—Staff writer Natasha S. Whitney can be reached at nwhitney@fas.harvard.edu.