NEWS We’re placing far too much hope in pulling carbon dioxide out of the air, scientists warn





The Wash­ing­ton Post,

Octo­ber 13, “We’re plac­ing far too much hope in pulling car­bon diox­ide out of the air, sci­en­tists warn”

In the past decade, an ambi­tious — but still mostly hypo­thet­i­cal — tech­no­log­i­cal strat­egy for meet­ing our global cli­mate goals has grown promi­nent in sci­en­tific dis­cus­sions. Known as “neg­a­tive emis­sions,” the idea is to remove car­bon diox­ide from the air using var­i­ous tech­no­log­i­cal means, a method that could the­o­ret­i­cally buy the world more time when it comes to reduc­ing our over­all greenhouse-​​gas emissions.

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Recent mod­els of future cli­mate sce­nar­ios have assumed that this tech­nique will be widely used in the future. Few have explored a world in which we can keep the planet’s warm­ing within at least a 2-​​degree tem­per­a­ture thresh­old with­out the help of negative-​​emission tech­nolo­gies. But some sci­en­tists are argu­ing that this assump­tion may be a seri­ous mistake.

In a new opin­ion paper, pub­lished Thurs­day in the jour­nal Sci­ence, cli­mate experts Kevin Ander­son of the Uni­ver­sity of Man­ches­ter and Glen Peters of the Cen­ter for Inter­na­tional Cli­mate and Envi­ron­men­tal Research have argued that rely­ing on the uncer­tain con­cept of neg­a­tive emis­sions as a fix could lock the world into a severe climate-​​change pathway.

[If] we behave today like we’ve got these get-​​out-​​of-​​jail cards in the future, and then in 20 years we dis­cover we don’t have this tech­nol­ogy, then you’re already locked into a higher tem­per­a­ture level,” Peters said.

Many pos­si­ble negative-​​emission tech­nolo­gies have been pro­posed, from sim­ply plant­ing more forests (which act as car­bon sinks) to design­ing chem­i­cal reac­tions that phys­i­cally take the car­bon diox­ide out of the atmos­phere. The tech­nol­ogy most widely included in the mod­els is known as bioen­ergy com­bined with car­bon cap­ture and stor­age, or BECCS.

In a BECCS sce­nario, plants cap­ture and store car­bon while they grow — remov­ing it from the atmos­phere, in other words — and then are har­vested and used for fuel to pro­duce energy. These bioen­ergy plants will be out­fit­ted with a form of tech­nol­ogy known as car­bon cap­ture, which traps car­bon diox­ide emis­sions before they make it into the atmos­phere. The car­bon diox­ide can then be stored safely deep under­ground. Even more car­bon is then cap­tured when the plants grow back again.

The idea sounds like a win-​​win on paper, allow­ing for both the removal of car­bon diox­ide and the pro­duc­tion of energy. But while more than a dozen pilot-​​scale BECCS projects exist around the world, only one large-​​scale facil­ity cur­rently oper­ates. And sci­en­tists have seri­ous reser­va­tions about the technology’s via­bil­ity as a global-​​scale solution.

First, the sheer amount of bioen­ergy fuel required to suit the mod­els’ assump­tions already poses a prob­lem, Peters told The Wash­ing­ton Post. Most of the mod­els assume a need for an area of land at least the size of India, he said, which prompts the ques­tion of whether this would reduce the area avail­able for food crops or force addi­tional defor­esta­tion, which would pro­duce more car­bon emissions.

When it comes to car­bon cap­ture and stor­age, the tech­nol­ogy has been used already in at least 20 plants around the world, not all of them devoted to bioen­ergy. In fact, car­bon cap­ture and stor­age can be applied in all kinds of indus­trial facil­i­ties, includ­ing coal-​​burning power plants or oil and nat­ural gas refiner­ies. But the tech­nol­ogy has so far failed to take off.

Ten years ago, if you looked at the Inter­na­tional Energy Agency, they were say­ing by now there would be hun­dreds of CCS plants around the world,” Peters said. “And each year the IEA has had to revise their esti­mates down. So CCS is one of those tech­nolo­gies that just never lives up to expectations.”

This is largely a mar­ket prob­lem, accord­ing to Howard Her­zog, a senior research engi­neer and car­bon cap­ture expert at Mass­a­chu­setts Insti­tute of Technology.

There’s no doubt you can do it,” he said. “We have coal plants that do CCS, you can have bio­mass that can do CCS — the technology’s not a big deal. The ques­tion is the economics.”

Because it’s more expen­sive to pro­duce energy with car­bon cap­ture than with­out it, there’s lit­tle incen­tive for the pri­vate sec­tor to invest in the tech­nol­ogy with­out a more aggres­sive pol­icy push toward cur­tail­ing emis­sions, he pointed out. A car­bon price, for instance, would be one way of cre­at­ing a mar­ket for the technology.

It’s not that the mod­el­ers have no rea­son for incor­po­rat­ing BECCS so heav­ily, though. Over a long enough time period, and at the scale needed to make a dent in our global cli­mate goals — espe­cially assum­ing a high enough car­bon price in the future — it may be the cheap­est mit­i­ga­tion tech­nol­ogy, Peters said. But this may not be enough for pol­i­cy­mak­ers to invest in its advance­ment now.

Decision-​​makers today don’t opti­mize over the whole cen­tury,” he said. “They’re not ask­ing: What tech­nol­ogy can I put in place now to make a profit in 100 years? So the sort of strate­gic think­ing in the model is dif­fer­ent from strate­gic think­ing in practice.”

Addi­tion­ally, the mod­els that are com­monly relied on to project future cli­mate and tech­no­log­i­cal sce­nar­ios assume that the CCS tech­nique works per­fectly within the next few decades, when it’s only just emerging.

The mod­els don’t have tech­ni­cal chal­lenges; they don’t run into engi­neer­ing prob­lems; the mod­els don’t have cost over­runs,” Peters said. “Every­thing works as it should work in the model.”

The bot­tom line, he and Ander­son note in their paper, is that all these assump­tions make for a huge gam­ble. If pol­i­cy­mak­ers decide we’re going to meet our cli­mate goals only with the aid of negative-​​emission tech­nolo­gies, and then these tech­nolo­gies fail us in the future, we will already be locked into a high-​​temperature cli­mate scenario.

In this light, the authors write, “negative-​​emission tech­nolo­gies should not form the basis of the mit­i­ga­tion agenda.” Indeed, they con­clude, nations should pro­ceed as though these tech­nolo­gies will fail, focus­ing instead on aggres­sive emissions-​​reduction poli­cies for the present, such as the con­tin­ued expan­sion of renew­able energy sources.

Other sci­en­tists agree. Daniel Kam­men, an energy pro­fes­sor at the Uni­ver­sity of Cal­i­for­nia in Berke­ley and direc­tor of the Renew­able and Appro­pri­ate Energy Lab­o­ra­tory, has pub­lished sev­eral recent papers on BECCS tech­nol­ogy, and agrees that it is “nowhere near ready to be con­sid­ered a com­po­nent of a viable car­bon reduc­tion strategy.”

For Kam­men and RAEL’s papers on BECCS using both the  SWITCH model and based on a chem­i­cal engi­neer­ing fea­si­bil­ity assess­ment, see:  the RAEL pub­li­ca­tions link, here.

Her­zog also agreed that “the focus of today should be on mit­i­ga­tion as opposed to wor­ry­ing about neg­a­tive emis­sions some­time in the future.” In the future, he said, as we approach the end of our decar­boniza­tion schemes, neg­a­tive emis­sions could still have a place when it comes to off­set­ting car­bon from those last activ­i­ties it’s most dif­fi­cult or most expen­sive to decarbonize.

But Her­zog added that, in his opin­ion, we’ve likely already over­shot a 2-​​degree tem­per­a­ture thresh­old, to say noth­ing of the more ambi­tious 1.5-degree tar­get described in the Paris cli­mate agree­ment. At the very least, he noted, a reliance on renew­ables alone would be unlikely to get us there, if it were still pos­si­ble. Indeed, mul­ti­ple recent analy­ses have sug­gested that the com­bined pledges of indi­vid­ual coun­tries par­tic­i­pat­ing in the Paris Agree­ment — very few of which have even con­sid­ered neg­a­tive emis­sions — still fall short of our tem­per­a­ture goals.

I think what you’re going to see in the long run is a mix of tech­nolo­gies com­ing in to help solve the prob­lem,” he said. “You need a mix of renew­ables, effi­ciency, nuclear, CCS, lifestyle changes — just a whole litany.”

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