At last week’s climate summit, there was a lot of talk about climate tech and how it could help countries meet their splashy new climate goals. A couple of the emerging technologies that got the most hype — carbon capture and green hydrogen — already have somewhat of a checkered track record. But leaders from big economies like Japan, Australia, Russia, and the US still hailed them as the key to slashing greenhouse gas emissions from some of the peskiest polluting industries.

“We’ve got to be constantly original and optimistic about new technology,” UK Prime Minister Boris Johnson said during the summit. “We need the scientists and all of our countries to work together to produce the technological solutions that humanity is going to need — whether it’s carbon capture and storage, or solving the problems of cheap hydrogen delivery.”

President Joe Biden’s virtual climate summit was aimed at encouraging individual countries to raise their climate ambitions. Last week, the US committed to reducing its greenhouse gas emissions this decade by roughly half compared to peak polluting levels. Japan and Canada made similar announcements, while the UK announced a bigger reduction goal for 2035. It’s all part of a race to do what scientists have found is necessary to prevent the worst effects of climate change: get greenhouse gas emissions near zero by 2050.

None of those goals can be achieved without switching out fossil fuels with renewable energy. That’s definitely the case for some of the biggest sources of planet-heating carbon dioxide emissions — like the power sector, which can swap coal and natural gas for wind turbines and solar panels. But some industries, like construction and shipping will have a much harder time getting rid of their emissions through renewables.

For these so-called “hard-to-decarbonize” industries, alternative fuel like green hydrogen or technologies that capture their CO2 emissions might offer a solution. But they’ll need to be developed and deployed carefully to avoid pitfalls that could derail the efforts to wean the world off fossil fuels. Take a look at what carbon capture technologies and green hydrogen might actually be able to achieve, along with some caveats.

Carbon capture

Carbon capture technologies can scrub CO2 out of polluters’ emissions so that it doesn’t enter the atmosphere in the first place. The technology can be added to a coal-fired power plant or steel mill, where it separates carbon dioxide from other gases. The carbon dioxide can be compressed and transported so that it can be stored in underground reservoirs or packaged as a commodity to be used in things like soda pop. The White House released a white paper on Friday that describes its potential for cleaning up industries like steel and cement — sectors that will likely play a big role in building out clean energy infrastructure, but which release a lot of CO2 in the process.

“Retrofitting our existing manufacturing infrastructure with these carbon capture and storage projects is where we’re going to get the biggest bang for our buck on the climate,” says Noah Deich, president of the nonprofit Carbon180, which advocates for the carbon removal technologies. We might be able to make these things without generating carbon dioxide within a couple decades, he says, but we don’t have the time to wait for that to happen. Getting rid of carbon dioxide released from cement manufacturing alone would be enormous progress; it would take a hefty 8 percent chunk out of global emissions.

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The Department of Energy announced $75 million in funding on April 23rd for carbon capture projects that could be used for steel, cement, or power plants. For some experts and environmental advocates, using carbon capture in the steel and cement industries makes sense — it’s when carbon capture gets paired with fossil-fueled power plants where the strategy can run into trouble.

While capturing carbon from polluting power plants helps avoid climate disaster, it doesn’t necessarily address the environmental destruction caused by drilling, mining, and fracking for fossil fuel. Nor does it eliminate the dangers, like spills and other pollution, which worries many people living in communities near pipelines and fossil fuel infrastructure. Captured carbon can also be shot into the ground to extract hard-to-reach fossil fuel reserves, perpetuating a polluting cycle. It’s no wonder, then, that oil companies and big oil-producing countries like the United Arab Emirates are promoting this tech. That’s why critics like Bernie Sanders and environmental justice groups have called carbon capture a “false solution.”

Carbon capture technology is also still very expensive, so much so that mounting costs led the only carbon capture coal plant in the US to shutter this year. “It teaches us a lot of lessons about what types of carbon capture projects make the most sense in the long run,” Deich says.

Carbon capture enthusiasts, however, believe costs will fall as the technology improves and more people adopt it, just as they did for renewable energy. Major investment — from governments or the private sector — could add to that trend. American tech companies have embraced similar technologies that pull carbon dioxide directly out of the atmosphere. So-called carbon removal or negative emissions tech is even more fledgling, but it doesn’t need to be tied to a source of pollution to yield CO2 reductions. Microsoft and Stripe have pledged to use it to cancel out their emissions using it, and their buy-in is crucial to bringing down the exorbitant costs still associated with the technology.

Hydrogen

On the other side of the world, green hydrogen is making a splash. “In the United States, you have the Silicon Valley. Here in Australia, we are creating our own hydrogen valleys where we will transform our transport industries, our mining and resource sectors, our manufacturing, and our fuel and energy production,” Australia Prime Minister Scott Morrison said during the first day of the summit.

So what is green hydrogen and how can it do all those things Morrison says it will? Hydrogen as a fuel has actually been around for a long time, but it’s been getting a lot more hype lately because of the rising demand for clean energy. Hydrogen fuel releases water when burned, but its carbon footprint actually depends on how the fuel is made. It can be made through electrolysis: splitting water to get to the hydrogen. Or it can be made through a process in which steam reacts with some kind of fossil fuel — usually gas — to separate out the hydrogen.

Crucially, it’s starting to get cheaper to make green hydrogen — which is made using electrolysis powered by renewable energy. Then there’s “blue” hydrogen that’s really just hydrogen made using fossil fuels paired with carbon capture, which comes with some of the same concerns as carbon capture paired with dirty power plants. Most hydrogen fuel is still made with natural gas, so turning it into blue hydrogen could give the gas industry a crutch in a future where fossil fuels aren’t as common.

Image: Jonas Güttler / picture alliance via Getty Images

In a future that avoids climate catastrophe, green (and, some say, blue) hydrogen might help power ships and planes. It could even replace coke and coal in steel and cement manufacturing. But while it holds a lot of promise, hydrogen is expensive, explosive, and difficult to transport. On the last day of the summit, US Energy Secretary Jennifer Granholm set a goal of cutting hydrogen costs by 80 percent by 2030 to make it “competitive with natural gas.” Hydrogen also needs a lot of investment in new pipelines, fueling stations, and storage. All of those things have held it back in the past.

That lack of infrastructure has stalled the development of hydrogen-powered cars, so the future of ground transportation is increasingly electric. But container shipping is one potential bright spot for hydrogen. With 90 percent of global trade transported by sea, shipping accounts for about 3 percent of global emissions (slightly more than the aviation industry). The International Maritime Organization set a target of halving the industry’s emissions by 2050, a goal that will likely depend on the availability of alternative fuels like hydrogen — especially since batteries aren’t advanced enough to power ships the size of skyscrapers.

To overcome the hurdles that have stood in hydrogen’s way in the past — between now and 2050, when economies are supposed to reach net zero greenhouse gas emissions — “every week is infrastructure week,” says Julio Friedmann, a senior research scholar at Columbia University.

The same could be said for nearly every piece of the future clean energy economy — whether it’s green hydrogen, carbon capture, or clean energy. And while hydrogen and carbon capture might play supporting roles in efforts to avert a deeper climate crisis, they’re still no replacement for expediting the transition from fossil fuels to more renewable energy. Australia, for example, still has a lot of work to do on all fronts. It has abundant solar and wind resources, which Friedmann says is a boon for the country’s green hydrogen ambitions. But the country still primarily relies on coal for its electricity generation. So Australia, like the rest of the world, will need to find the right balance of phasing out the old and bringing in the new to usher in a more sustainable future.