Até onde a tecnologia poderia reverter as mudanças climáticas?

The Petra Nova facility in Texas will capture more than 1 million tons of CO2 annually. NRG Energy.

How Far Can Technology Go to Stave Off Climate Change?

With carbon dioxide emissions continuing to rise, an increasing number of experts believe major technological breakthroughs — such as CO2 air capture — will be necessary to slow global warming. But without the societal will to decarbonize, even the best technologies won’t be enough.

By David Biello • January 18, 2017

The U.S. now has two coal-burning power plants that avoid dumping carbon dioxide into the air. Petra Nova in Texas and Kemper in Mississippi use technology to stop CO2 in the smokestack and before combustion, respectively. Unfortunately, that makes two out of more than 400 coal-fired power plants in the U.S., the rest of which collectively pour 1.4 billion metric tons of the colorless, odorless greenhouse gas into the atmosphere each year. Even Kemper and Petra Nova do not capture all of the CO2 from the coal they burn, and the captured CO2 is used to scour more oil out of the ground, which is then burned, adding yet more CO2 to the atmosphere. The carbon conundrum grows more complex — and dangerous — with each passing year.

In a world with thousands of coal-fired power plants, nearly 2 billion cars and trucks, and billions of tons of coal, oil, and natural gas mined and combusted, it is no surprise that some 40 billion metric tons of CO2 are discharged into the atmosphere annually. The oceans and the world’s plants absorb some, yet concentrations of CO2 in the atmosphere inexorably rise year by year, climbing in 2016 past 400 parts per million, compared to 280 before the Industrial Revolution. This is setting off changes from a meltdown in the Arctic, to thawing glaciers worldwide, to weird weather and rising seas. Indeed, the atmosphere has now accumulated enough CO2 to stave off the next ice age for millennia, and every person on Earth now breathes air unlike that inhaled by any previous member of our species, Homo sapiens.

In a world with thousands of coal-fired power plants, nearly 2 billion cars and trucks, and billions of tons of coal, oil, and natural gas mined and combusted, it is no surprise that some 40 billion metric tons of CO2 are discharged into the atmosphere annually.

To have any hope of slowing such pollution and, ultimately, reversing it, will require an energy revolution and some game-changing technological breakthroughs. After all, it took the advent of cheap methods to fracture underground shale rock with high-pressure water and sand — the technique known as fracking — to free natural gas and make it cheap enough to begin to kill coal in the U.S. As a result of this cheap natural gas freed by fracking, U.S. emissions of CO2 are now back down to levels last seen in the last decade of the 20th century. Of course, natural gas is still a fossil fuel and fracking generates sizable leaks of methane, a potent greenhouse gas. So even though fracked natural gas is an improvement over coal, it still adds to the relentless buildup of CO2.

The key question is: Can engineers and entrepreneurs invent and deploy enough technologies — and the world’s governments adopt the right incentives and policies to eliminate carbon from the global economy — all in time to avert major upheaval from climate change? Already, technological advances are making clean energy sources such as solar and wind more efficient and cheaper, leading to steady growth in their deployment. But renewable energy increases are still being outrun by even-faster increases in fossil fuel consumption as the economies of developing nations like China and India grow and developed nations, such as the U.S., do far too little to wean themselves off oil, coal, and natural gas.

This lack of progress underscores the urgent need for technological innovations, although deploying technologies at the scale needed to significantly slow climate change will require major government expenditures and, hence, a massive dose of global will that has so far been lacking. Some of these technologies may not even be on the horizon, but one tool that many experts say will have to be used is the removal of CO2 from the atmosphere.

Oliver Geden, a climate analyst and head of the European Union research division at the German Institute for International and Security Affairs, says it’s “pretty clear” that without carbon removal technologies, the world community will not reach the goals agreed upon in Paris of limiting temperature increases to 1.5 or 2 degrees C (2.7 to 3.6 F). Even the U.N. Intergovernmental Panel on Climate Change (IPCC) estimates that a massive amount of CO2 removal will be required this century — at least 500 billion metric tons pulled back out of the air — if we are to avoid the worst of global warming. But Geden adds, “At the same time, you can observe a tendency to avoid even talking about carbon removal strategies.” 

Deploying technologies to significantly slow climate change will mean major government expenditures.

The IPCC went so far as to name a preferred technological breakthrough: bioenergy with CO2 capture and storage, or BECCS for short. These facilities resemble coal-fired power plants, but use recently grown energy crops rather than fossilized swamp plants as fuel and capture the CO2 from combustion. Since the crops, such as fast-growing trees and switchgrass, had to pull CO2 out of the atmosphere in order to grow, such power plants could suck CO2 out of the sky rather than adding long-buried carbon as coal does.

But no such facility currently exists. The closest is a brewery for corn ethanol in Illinois that captures the CO2 from fermentation and then buries it in a deep saline aquifer. Worse, to replace all the coal burned around the world would put such energy crops into competition with food crops for the available farmland.

So what are the alternatives to BECCS for a CO2 cure? One would be to enhance natural methods for capturing CO2. After all, forests on land and at sea help pull CO2 out of the air and incorporate it into trees, kelp, and even microscopic diatoms. Even better, new genetic techniques or other manipulations may enable scientists to enhance photosynthesis itself, allowing plants to capture more CO2 as well as yield more food, fiber, or fuel. Some crop plants such as corn and sugarcane are already more efficient at capturing CO2 than others such as wheat or rice. Simply enhancing all crops’ ability to take in CO2 and make use of it could help remedy the CO2 challenge, as would increasing the amount of carbon in the world’s fertile soils or buried beneath the sea. Research projects along these lines are being pursued at university and government labs in many countries. The U.S. Department of Energy, for example, has developed the PETRO program, which stands for “plants engineered to replace oil.”

But, just as with BECCS, there is only so much room on land and at sea for even enhanced plants to remove CO2 — and people still want fuels to generate electricity and propel travel on land, at sea, and in the air. Biofuels may prove an adequate solution for aviation, but present a host of problems when applied to the challenge of nearly 2 billion vehicles worldwide. Artificial photosynthesis or other CO2-to-fuel technologies could close the carbon loop for transportation, but remain a long way from escaping the science lab. Electric cars and trucks — which are already on the road and perhaps could eventually be of the self-driving variety — may prove the key to eliminating oil use in transportation.

Of course, that requires generating electricity from sources that don’t emit CO2, such as the wind, sun, hot rocks beneath the ground, or the fission of radioactive elements like uranium and thorium. But making a wind turbine or a nuclear power plant still requires plastics, steel, and concrete, all of which currently require CO2 emissions to manufacture. So the world needs to find CO2-free ways of making steel and concrete.

The Treepods concept (shown here) is one of various carbon-capture technologies that act like artificial trees, sucking CO2 from the air through their canopies. Influx_Studio/ShiftBoston.

“Considering energy alone, current emissions will see the 1.5-C carbon budget used up in between three and 13 years,” says Kevin Anderson, a climate and energy researcher at the University of Manchester in the U.K. In fact, Anderson argues that to have any hope of restraining global warming to 2 degrees C, nations like the U.S., Japan, and Germany would have to eliminate CO2 emissions from electricity generation and transportation by 2035, and developing nations like China would need to reach maximum emissions by 2025 and then begin to decline.

That leaves the world in need of another potential technology savior: machines to suck CO2 out of the air, a kind of artificial tree. Such machines exist and have been demonstrated from the mountains of Switzerland to the dry desert air of Phoenix and the forested hillsides of British Columbia, but many more of them would be required. In fact, it would take on the order of 100 million artificial trees to counteract the 40 billion metric tons of CO2 added to the atmosphere each year. For comparison, automakers currently manufacture around 80 million cars per year.

But there’s worse news. “There are almost no business cases for carbon removal right now,” Geden notes. In other words, it still costs nothing to spew CO2 into the sky, so people have no financial incentive to stop dumping, let alone pay to clean up the air. This reality has bedeviled efforts to build coal-fired power plants with CO2 capture and storage, let alone machines to capture the more diffuse CO2 in the air.

To change that economic reality would require either a price to be put on CO2, making it more expensive to emit, or mandates to reduce or eliminate CO2 pollution — both of which highlight a need for the political will to take action. That will is certainly lacking in the Trump administration, as well as in the Republican-controlled U.S. Congress, to say nothing of the rest of the world.

Hopefully, it will not take a climate catastrophe to motivate such action, such as the drowning of some coastal city, or the embrace of more extreme “geoengineering” interventions such as adding sulfuric haze to the stratosphere to cool the planet. That’s why experts like Anderson say the most necessary breakthrough is not technological, it’s psychological — and moral.

What the world needs is not a miracle, says Anderson, “but shovel-sized dollops of courage, innovative thinking, and Marshall-style construction programs, and an acknowledgment that we have to escape failed paradigms. Not easy, but achievable, if we really do love our children.”

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David Biello is the author of The Unnatural World: The Race to Remake Civilization in Earth's Newest Age. He has been covering energy and the environment for more than a decade and is the science curator for TED as well as a contributing editor for Scientific American.

Fonte: Yale Environment 360

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LEIA TAMBÉM:

Psiquiatra e historiador analisa a tomada de consciência da população sobre as mudanças climáticas