As the world digs into the technologies that could help society tackle climate change, controversy is inevitably emerging in key areas.

Environmentalists, and some of their Democratic colleagues in the U.S. Congress, are concerned that hydrogen and technology capturing carbon from polluting facilities could prolong the use of oil and gas products and not actually fight climate change.

I posed that sentiment to U.S. Energy Secretary Jennifer Granholm in previously unpublished footage of Cipher’s inaugural Newsmakers interview. Her answer:

Discord over technology preference has been simmering for years among all facets of our society that otherwise generally agree climate change is a crisis that we must urgently tackle.

It’s a complex debate for sure, but to boil it down, it goes like this: One viewpoint advocates for wind and solar power to fuel nearly all of our economy to the exclusion of other clean technologies.

Another viewpoint posits that we need an energy mix that includes renewable energy alongside other clean technologies like nuclear power (long controversial among progressives), carbon capture tech and—more recently—clean hydrogen.

This discord is coming to a head now because Democrats control Washington and have the power to move policy. Progressive leaders on Capitol Hill, led by Sen. Bernie Sanders of Vermont, have been vocal supporting the first viewpoint.

President Biden and the rest of his administration have staked their position firmly in the latter camp, particularly because renewable energy on its own can’t clean up some sectors of the economy like manufacturing. Clean hydrogen and carbon capture, both of which don’t exist commercially (yet), are examples of the type of tech that could help clean up the manufacturing of ubiquitous materials like steel and cement.

Sen. Joe Manchin (D-W.Va.), a pivotal vote for the Democratic Party, is also pushing for carbon capture technology for natural gas and coal plants (the latter is unlikely to be economic in any case).

The Senate-passed infrastructure bill has billions in funding for nearly all types of cleantech, reflecting the viewpoint pushing a broader clean-energy mix: wind, solar, electric cars, clean hydrogen, carbon capture and nuclear power.

Recent studies by BloombergNEF and Princeton University have shown how vastly different zero-carbon energy mixes could take shape. Wind and solar are poised to grow rapidly in nearly all scenarios, though carbon-capture tech and nuclear power could play larger roles depending on how politicians and investors steer government support and money.

In fact, BloombergNEF found that an energy mix relying heavily on carbon capture could be less expensive than one relying heavily on clean electricity and hydrogen produced from renewable energy. Importantly, however, its report didn’t include all costs, including fuel costs, which could make the carbon capture scenario comparatively more expensive.

It’s imperative that technologies like carbon capture tech, nuclear power and hydrogen do, in fact, cut carbon emissions as envisioned.

Most carbon capture projects started over the past three decades have failed, according to a new peer-reviewed study. That study doesn’t say such a track record means society should stop trying but instead offers ways to improve projects’ viabilities going forward.

For its part, hydrogen is a ubiquitous material that could be used in many different energy applications such as manufacturing and energy storage. In the wake of the pandemic, support has suddenly skyrocketed for it, particularly “green” hydrogen made from water and renewable electricity and also “blue” hydrogen made from natural gas with carbon capture technology.

But questions have been raised about the cleanliness of “blue” hydrogen, given the track record of carbon capture generally and because gas’s main ingredient, methane, is a potent greenhouse gas.

“It will be part of our energy transition, if we make sure that there is not methane leakage from the natural gas,” Granholm said when asked about blue hydrogen. She said she prefers green hydrogen, but that if you can “remove the methane pollution from the natural gas fueling of blue hydrogen, then you will have come a long way toward creating another dispatchable zero-carbon energy source.”

As for nuclear power, it undeniably provides a majority of America’s carbon-free power, but worries linger, chiefly: where to store radioactive waste and the time it takes to build new plants.

Granholm said the department will soon launch a “consent-based siting process” to store nuclear waste, which means that communities willing to take it will receive compensation while the department works to support advanced reactors that create less waste.

On that front, Granholm is worried about the clock winding down to the net-zero emissions goal by 2050: “For me, the biggest challenge on nuclear is that a new plant takes a lot of time, and we just don’t have a lot of time.”