Captured CO2 is used commercially for everything from adding bubbles to soda to extracting oil from wells. But the demand for CO2 is lower than the total amount available. If direct air carbon capture technology develops further, the captured carbon might be stored in saline aquifers deep in the earth, or in volcanic basalt under the ocean. Some are concerned that sequestered carbon might not stay sequestered; if CO2 leaked into groundwater aquifers it could make those aquifers unsafe for drinking. Gas that leaked back out into the air would be very unlikely to pose any threat to humans but would slowly undo any of the gains from capturing the carbon in the first place.
“All renewables are improving and all are growing,” said Nemet. Solar, wind, geothermal, hydroelectric: There are plenty of renewable energy sources already in use around the world. But one stands out from the pack. “Solar photovoltaics are improving (mainly getting less expensive) faster than any of the others,” Nemet said.
Solar energy is the fastest-growing energy source in the U.S. but is limited by problems with storage and distribution. This summer, a team at the University of Exeter in England found that angling solar panels in the same way some butterflies warm their wings before flight can increase the amount of power produced by those panels almost 50 percent. In November, a California team proposed a system to store excess energy from peak times underground to be used when raw energy is less available. They pointed to a community in Canada that already uses solar energy to heat water during the summer and then stores the warm water 120 feet underground, which provides enough warmth to heat homes through the winter.
Nuclear energy is a divisive topic. It offers zero carbon emissions at the cost of a potential meltdown. Increasing attention has been paid to the potential of using thorium for nuclear fission instead of uranium. According to some estimates, thorium reactors could produce only a thousandth of the waste of current reactors. It’s also much harder to weaponize.
Alternately, some researchers hope to do away with fission altogether. Science fiction writers have long dreamed humanity might be able to harness nuclear fusion, the same process that powers the sun. Fusion reactors wouldn’t have the same risk of explosion as fission reactors, and the process would release three to four times the amount of energy. Last year, Lockheed Martin announced that it had developed a breakthroughcompact fusion machine, the small size of which would make the released energy easier to control and use. The company expects to have a prototype in five years. Meanwhile, MIT has announced their own fusion project that uses magnetic fields for an ARC reactor: “affordable, robust, compact.”
Films like Mad Max: Fury Road hint at a terrifying future in which people fight to the death over water. And as polar ice caps melt into the sea, the world’s supply of freshwater is depleted. Water supplies could become even more limited as climate change reduces rainfall in some regions. Currently, desalination processes use more fossil fuels than shipping in water from elsewhere, but more energy-efficient systems are in developments. A new type of graphene membrane—only one atom thick—could drastically reduce the amount of energy needed to move water through the desalination process. However, experts warn that the leftover salt could threaten ocean life if not disposed of carefully.
In the context of climate change, geoengineering encompasses any attempt to modify the Earth’s climate. The National Research Councilpublished a report in February evaluating current theories of geoengineering and arguing for federal funding to support further research. The council was particularly interested in exploring solar radiation management techniques, which would cool the Earth by reflecting more sunlight away from the planet. Although some see geoengineering as the Earth’s only viable future, to others the idea of messing with the Earth’s atmosphere or oceans to alleviate the consequences of manmade climate change seems horrifically irresponsible. On Slate, geophysicist Raymond Pierrehumbert wrote that “the idea of ‘fixing’ the climate by hacking the Earth’s reflection of sunlight is wildly, utterly, howlingly barking mad.” Others are worried about the moral implication of relying on the ability to fix climate change retroactively. “Just knowing that [these methods] are available is likely to reduce the world’s collective motivation to do the hard work of reducing emissions,” said Nemet. “But trying to address climate change without them as a backup plant might be even riskier.”
There are a variety of hypothesized methods of solar radiation management, although most have been tested only using computer models. Scientists could spray aerosols into the stratosphere or inject seawater into clouds to whiten them. Both methods would theoretically cause fewer of the sun’s rays to reach the Earth’s surface. Closer to the ground, roofs could be painted white for the same reason, although the total surface area of roofs across the globe is so small that this would have a limited effect. None of these tactics make the underlying issues of carbon dioxide go away, but climate change predictions are now dire enough that geoengineering may soon get some real-world trials. In 2014 a group led by Harvard professor David Keith published a “road map” for actually releasing small amounts of sea salt, sulphur ions, and other substances into the atmosphere to study their effects on clouds and the ozone layer.
Multiple companies are developing modern airships (a synonym for “dirigible” less likely to cause Hindenburg flashbacks), which use less fuel than cargo planes and can travel faster and to more remote locations than cargo ships. There is the Aeroscraft, which would move four times faster than a cargo ship and could carry twice the amount of a cargo plane, and the LMH-1, a hybrid airship that uses suction to land, meaning it doesn’t even require landing masts. Still in the concept stage is the High Speed Solar Airship, which would use a combination of thin solar panels and the wind of the Jet Stream. There would be no fuel costs. Remote regions that to this point can be accessed only by slashing down forests and building roads could be within more sustainable reach.
Closer to the ground, vacuum trains, like Elon Musk’s Hyperloop, could simultaneously speed up transit and reduce reliance on fossil fuels. Passengers would travel in pods inside low-pressure tubes. Magnets would accelerate the pods, and solar panels would power the entire system. Musk is building a track to test the feasibility of larger development.
Biofuels are not new. Henry Ford’s first car was designed to run onethanol, made from corn, beets, and other plants. But much of the energy spent producing ethanol comes from coal, so researchers are working with other potential fuel sources. Some have developed a process to convert sugar to hydrogen, which can then be used in a fuel cell. For those concerned about biofuel production threatening food production, there’s algae, which can be converted into biodiesel, biogasoline, jet fuel, and more. Algae can be grown vertically, reducing the amount of space diverted from growing other crops. Although algae-based fuel does release carbon dioxide, it’s the carbon dioxide that the algae has absorbed during its lifetime, not the previously sequestered CO2 released by fossil fuels. Algae also yields almost 2,000 times more biofuel per acre per year than corn.
For many forms of renewable energy, price is a limiting factor. Despite predictions of the devastating long-term costs of burning fossil fuels (more powerful hurricanes alone have caused over $14 billion in damage since 2005), many people are swayed by the cheap cost of coal and oil compared to solar or wind energy. One way to bring down the cost of renewable energy is to improve energy storage systems. Katharine Hayhoe, an atmospheric scientist and director of the Climate Science Center at Texas Tech University, told the New Republic, “The single technology that will make the most difference is not energy generation: it’s energy storage. We need cheap, reliable batteries for when the sun doesn’t shine and the wind doesn’t blow.” Build a better battery and clean energy could be stored on wind or solar farms and then used to light up homes, run cars, and even power industry.
The biggest struggle in developing a better battery—one that can store more and is less likely to burst into flames than current lithium ion batteries used in smartphones and some electric cars—is scaling up from a lab setting to commercial production. Tesla is sticking with lithium ion batteries but hugely scaling up manufacturing. By the time the company’sGigafactory in the Nevada desert is fully running in 2020 it will produce as many batteries in a year as were produced worldwide in 2013.
If other companies can learn from Tesla, more ground-breaking battery types might become widely available. Air-based batteries (zinc-air, aluminum-air, and more) would be able to draw on air from the environment. Israeli company Phinergy says its aluminum-air batteries could give electric cars a range of 1,000 miles (the current average is less than 100 on a full charge). A big drawback to aluminum-air batteries is that the metal degrades, making them hard to recharge.
While air battery companies work on solving that problem, a company called Ambri is developing a liquid-metal battery in which two layers of liquid metal are separated by a layer of molten salt. A liquid-metal battery could be used for large-scale grid energy storage. The wide availability of the batteries’ common-earth components mean it would be cheap to manufacture, and the company claims its design would have a very long life span of 300 years.
All emerging technologies face an uphill battle to get funding for research, experiments, and product development, and many good ideas die along the way. If the Paris climate talks can orient investors and policymakers toward encouraging climate innovation, good ideas—whether they’re the ones listed here or not—will have a better chance of making it out of the lab.