Direct CO2 Capture Machines Could Use ‘a Quarter of Global Energy’ in 2100
By Simon Evans
Machines that suck CO2 directly from the air could cut the cost of meeting global climate goals, a new study finds, but they would need as much as a quarter of global energy supplies in 2100.
The research, published Monday in Nature Communications, is the first to explore the use of direct air capture (DAC) in multiple computer models. It shows that a "massive" and energy-intensive rollout of the technology could cut the cost of limiting warming to 1.5 or 2 C above pre-industrial levels.
But the study also highlights the "clear risks" of assuming that DAC will be available at scale, with global temperature goals being breached by up to 0.8 C if the technology then fails to deliver.
This means policymakers should not see DAC as a "panacea" that can replace immediate efforts to cut emissions, one of the study authors tells Carbon Brief, adding: "The risks of that are too high."
DAC should be seen as a "backstop for challenging abatement" where cutting emissions is too complex or too costly, says the chief executive of a startup developing the technology. He tells Carbon Brief that his firm nevertheless will "continuously push back on the 'magic bullet' headlines."
The 2015 Paris agreement set a goal of limiting human-caused warming to "well below" 2 C and an ambition of staying below 1.5 C. Meeting this ambition will require the use of "negative emissions technologies" to remove excess CO2 from the atmosphere, according to the Intergovernmental Panel on Climate Change (IPCC).
This catch-all term covers a wide range of approaches, including planting trees, restoring peatlands and other "natural climate solutions." However, model pathways developed by researchers rely most heavily on bioenergy with carbon capture and storage (BECCS). This is where biomass, such as wood pellets, is burned to generate electricity and the resulting CO2 is captured and stored.
The significant potential role for BECCS raises a number of concerns, with land areas up to five times the size of India devoted to growing the biomass needed in some model pathways.
One alternative is direct air capture, where machines are used to suck CO2 out of the atmosphere. If the CO2 is then buried underground, the process is sometimes referred to as direct air carbon capture and storage (DACCS).
The new study explores how DAC could help meet global climate goals with "lower costs," using two different integrated assessment models (IAMs). Study author Dr. Ajay Gambhir, senior research fellow at the Grantham Institute for Climate Change at Imperial College London, explains to Carbon Brief:
"This is the first inter-model comparison … [and] has the most detailed representation of DAC so far used in IAMs. It includes two DAC technologies, with different energy inputs and cost assumptions, and a range of energy inputs including waste heat. The study uses an extensive sensitivity analysis [to test the impact of varying our assumptions]. It also includes initial analysis of the broader impacts of DAC technology development, in terms of material, land and water use."
The two DAC technologies included in the study are based on different ways to adsorb CO2 from the air, which are being developed by a number of startup companies around the world.
One, typically used in larger industrial-scale facilities such as those being piloted by Canadian firm Carbon Engineering, uses a solution of hydroxide to capture CO2. This mixture must then be heated to high temperatures to release the CO2 so it can be stored and the hydroxide reused. The process uses existing technology and is currently thought to have the lower cost of the two alternatives.
The second technology uses amine adsorbents in small, modular reactors such as those being developed by Swiss firm Climeworks. Costs are currently higher, but the potential for savings is thought to be greater, the paper suggests. This is due to the modular design that could be made on an industrial production line, along with lower temperatures needed to release CO2 for storage, meaning waste heat could be used.
Overall, despite "huge uncertainty" around the cost of DAC, the study suggests its use could allow early cuts in global greenhouse gas emissions to be somewhat delayed, "significantly reduc[ing] climate policy costs" to meet stringent temperature limits.
Using DAC means that global emissions in 2030 could remain at higher levels, the study says, with much larger use of negative emissions later in the century. This is shown in the charts, below, for scenarios staying below 1.5 C (left panel, shades of blue) and 2 C (right, green).
Pathways without DAC are shown in darker shades. For example, the solid dark blue line shows results from the "TIAM" model, with emissions peaking around 2020 and falling rapidly to below zero around 2050.
In contrast, the light blue solid line shows a pathway where DAC allows a more gradual decline, reaching zero in the 2060s and with negative emissions of around 30 billion tonnes per year (Gt/yr) by the 2080s. This is close to today's annual global emissions of around 40GtCO2/yr.
Global CO2 emissions from fossil fuels (Gt/yr) in model pathways consistent with limiting warming this century to 1.5 C (left panel, blue) or 2 C (right panel, green). Results from two different IAMs – TIAM and WITCH – are shown with solid and dashed lines, respectively. The various lines show scenarios that use direct capture ("DAC," darker shades) and those that do not ("NoDAC," lighter), as well as pathways to 2 C without negative emissions of any sort ("NoNET," darkest green). Source: Realmonte et al. (2019).
"The results of both models are surprisingly similar," says Dr. Nico Bauer, a scientist at the Potsdam Institute for Climate Impacts Research (PIK), who was not involved in the study. He tells Carbon Brief: "This increases the credibility about the main conclusions that the DACCS technology can play an important role in a long-term climate change mitigation strategy."
The use of DAC in some of the modeled pathways delays the need to cut emissions in certain areas. The paper explains: "DACCS allows a reduction in near term mitigation effort in some energy-intensive sectors that are difficult to decarbonise, such as transport and industry."
Steve Oldham, chief executive of DAC startup Carbon Engineering says he sees this as the key purpose of CO2 removal technologies, which he likens to other "essential infrastructure" such as waste disposal or sewage treatment.
Oldham tells Carbon Brief that while standard approaches to cutting CO2 remain essential for the majority of global emissions, the challenge and cost may prove too great in some sectors. He says:
"DAC and other negative emissions technologies are the right solution once the cost and feasibility becomes too great … I see us as the backstop for challenging abatement."
Even though DAC may be relatively expensive, the model pathways in the new study still see it as much cheaper than cutting emissions from these hard-to tackle sectors. This means the models deploy large amounts of DAC, even if its costs are at the high end of current estimates.
It also means the models see pathways to meeting climate goals that include DAC as having lower costs overall ("reduce[d]… by between 60 to more than 90%").
Gambhir tells Carbon Brief: "Deploying DAC means less of a steep mitigation pathway in the near-term, and lowers policy costs, according to the modeled scenarios we use in this study."
However, the paper also points to the significant challenges associated with such a large-scale, rapid deployment of DAC, in terms of energy use and the need for raw materials.
The energy needed to run direct air capture machines in 2100 is up to 300 exajoules each year, according to the paper. This is more than half of overall global demand today, from all sources, and despite rising demand this century, it would still be a quarter of expected demand in 2100.
Gambhir tells Carbon Brief:
"Large-scale deployment of DAC in below-2°C scenarios will require a lot of heat and electricity and a major manufacturing effort for production of CO2 sorbent. Although DAC will use less resources such as water and land than other NETs [such as BECCS], a proper full life-cycle assessment needs to be carried out to understand all resource implications."
There are also questions as to whether this new technology could be rolled out at the speed and scale envisaged, with expansion at up to 30% each year and deployment reaching 30GtCO2/yr towards the end of the century. This is a "huge pace and scale," Gambhir says, with the rate of deployment being a "key sensitivity" in the study results.
Professor Jennifer Wilcox, professor of chemical engineering at Worcester Polytechnic Institute, who was not involved with the research, says that this rate of scale-up warrants caution. She tells Carbon Brief:
"Is the rate of scale-up even feasible? Typical rules of thumb are increase by an order of magnitude per decade [growth of around 25-30% per year]. [Solar] PV scale-up was higher than this, but mostly due to government incentives … rather than technological advances."
Reaching 30GtCO2/yr of CO2 capture – a similar scale to current global emissions – would mean building some 30,000 large-scale DAC factories, the paper says. For comparison, there are fewer than 10,000 coal-fired power stations in the world today.
If DAC were to be carried out using small modular systems, then as many as 30m might be needed by 2100, the paper says. It compares this number to the 73m light vehicles that are built each year.
The study argues that expanding DAC at such a rapid rate is comparable to the speed with which newer electricity generation technologies such as nuclear, wind and solar have been deployed.
Climeworks greenhouse © Climeworks / Julia Dunlop
The modeled rate of DAC growth is "breathtaking" but "not in contradiction with the historical experience," Bauer says. This rapid scale-up is also far from the only barrier to DAC adoption.
The paper explains: "[P]olicy instruments and financial incentives supporting negative emission technologies are almost absent at the global scale, though essential to make NET deployment attractive."
Carbon Engineering's Oldham agrees that there is a need for policy to recognize negative emissions as unique and different from standard mitigation. But he tells Carbon Brief that he remains "very very confident" in his company's ability to scale up rapidly.
(The new study includes consideration of the space available to store CO2 underground, finding this not to be a limiting factor for DAC deployment.)
The paper says that the challenges to scale-up and deployment on a huge scale bring significant risks, if DAC does not deliver as anticipated in the models. Committing to ramping up DAC rather than cutting emissions could mean locking the energy system into fossil fuels, the authors warn.
This could risk breaching the Paris temperature limits, the study explains:
"The risk of assuming that DACCS can be deployed at scale, and finding it to be subsequently unavailable, leads to a global temperature overshoot of up to 0.8°C."
Gambhir says the risks of such an approach are "too high":
"Inappropriate interpretations [of our findings] would be that DAC is a panacea and that we should ease near-term mitigation efforts because we can use it later in the century."
"Policymakers should not make the mistake to believe that carbon removals could ever neutralise all future emissions that could be produced from fossil fuels that are still underground. Even under pessimistic assumptions about fossil fuel availability, carbon removal cannot and will not fix the problem. There is simply too much low-cost fossil carbon that we could burn."
Nonetheless, professor Massimo Tavoni, one of the paper's authors and the director of the European Institute on Economics and the Environment (EIEE), tells Carbon Brief that "it is still important to show the potential of DAC – which the models certainly highlight – but also the many challenges of deploying at the scale required."
The global carbon cycle poses one final – and underappreciated – challenge to the large-scale use of negative emissions technologies such as DAC: ocean rebound. This is because the amount of CO2 in the world's oceans and atmosphere is in a dynamic and constantly shifting equilibrium.
This equilibrium means that, at present, oceans absorb a significant proportion of human-caused CO2 emissions each year, reducing the amount staying in the atmosphere. If DAC is used to turn global emissions net-negative, as in the new study, then that equilibrium will also go into reverse.
As a result, the paper says as much as a fifth of the CO2 removed using DAC or other negative emissions technologies could be offset by the oceans releasing CO2 back into the atmosphere, reducing their supposed efficacy.
Reposted with permission from our media associate Carbon Brief.
EcoWatch Daily Newsletter
Coronavirus Shines Light on Zoos as Danger Zones for Deadly Disease Transmission Between Humans and Animals
By Marilyn Kroplick
The term "zoonotic disease" wasn't a hot topic of conversation before the novel coronavirus started spreading across the globe and upending lives. Now, people are discovering how devastating viruses that transfer from animals to humans can be. But the threat can go both ways — animals can also get sick from humans. There is no better time to reconsider the repercussions of keeping animals captive at zoos, for the sake of everyone's health.
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By Kate Whiting
Bernice Dapaah calls bamboo "a miracle plant," because it grows so fast and absorbs carbon. But it can also work wonders for children's education and women's employment – as she's discovered.
These are the world's most bicycle-friendly cities. Statista<p>"The reason we use bamboo to manufacture bicycles is because it's found abundantly in Ghana and this is not a material we're going to import," says Dapaah, one of the World Economic Forum's Young Global Leaders.</p><p>"It's a new innovation. There were no existing bamboo bike builders in our country, so we were the first people trying to see how best we could utilize the abundant bamboo in Ghana."</p>
<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="a335b5dffdd806bd6bb4debea90c2045"><iframe lazy-loadable="true" src="https://www.youtube.com/embed/dxsb9c4HMn0?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Supporting Students<p>Besides encouraging Ghanaians to swap vehicles for affordable bikes, Ghana Bamboo Bikes Initiative is helping students save time on walking to school so they have more time to learn.</p><p>Each time they sell a bike, they donate a bike to a schoolchild in a rural community, who might otherwise have to walk for hours to get to school.</p><p>Dapaah knows how transformative a shorter journey to school can be to academic performance. She grew up living with her <a href="https://www.youtube.com/watch?v=sb3joGYmx9A&feature=emb_logo" target="_blank">grandpa, a forester in a rural part of the country</a>.</p><p>"We had to walk three and a half hours every day before I could go to school. He later bought me a bike, so I finished senior high and wanted to go to university."</p><p>The experience inspired her to launch Ghana Bamboo Bikes Initiative with two other students at college.</p><p>"When we started this initiative, I looked back and said, when I was young, I had to walk miles before I could get to school, and sometimes if I was late, I was punished.</p><p>"Why don't we donate bikes for students to encourage them to study and so they can have enough time to be on books."</p><p>To date, they have sold more than 3,000 road, mountain and children's bikes – and Dapaah says they plan to donate <a href="https://www.entrepreneur.com/video/350343" target="_blank">10,000 bikes to schoolchildren over five years</a>.</p>
Empowering Women<p>The enterprise is also providing local jobs. It teaches young people to build bikes, particularly women and those in rural communities, where jobs can be scarce. More than 50% of people they have trained are women.</p><p>Dapaah says they want to boost the number of people they employ to 250 over the next five years and they are looking to partner with NGOs to build a childcare facility so mothers can continue to work.</p>
Reducing Emissions<p>By promoting a cycling culture in Ghana, Dapaah says they're also committed to reducing emissions in the transport sector and contributing to the UN's Sustainable Development Goals.</p><p>"I love the idea of reusing bamboo to promote sustainable cycling. People want to go green, low-carbon, lean-energy efficient," she says.</p>
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Deforestation coupled with the rampant destruction of natural resources will soon have devastating effects on the future of society as we know it, according to two theoretical physicists who study complex systems and have concluded that greed has put us on a path to irreversible collapse within the next two to four decades, as VICE reported.
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By Kristen Pope
Melting and crumbling glaciers are largely responsible for rising sea levels, so learning more about how glaciers shrink is vital to those who hope to save coastal cities and preserve wildlife.
Groans, Creaks, Icebergs’ Calving Splashes<p>Oskar Glowacki already knew that melting glacial ice sounds like frying bacon. As ice bubbles burst, anyone nearby can hear crackling and popping, said Glowacki, a postdoctoral scholar at the Scripps Institution of Oceanography. Using hydrophones, he and other scientists now can make more nuanced measurements of how a changing climate sounds underwater, from the groans, creaks and splashes of a calving iceberg to the changes in whale songs as the ocean warms.</p><p>Glowacki recently used a pair of hydrophones to study the underwater world of glaciers, publishing his findings in <a href="https://www.the-cryosphere.net/14/1025/2020/" target="_blank">The Cryosphere</a>. He and co-author Grant B. Deane measured glacier retreat by <a href="https://yaleclimateconnections.org/2020/07/melting-glaciers-sound-like-frying-bacon/" target="_blank">recording the sounds of ice</a> – from small chunks to enormous slabs – falling off the glacier and splashing into the water.</p><p>During the summer of 2016, Glowacki's team placed two hydrophones near Hansbreen Glacier in Hornsund Fjord, Svalbard. For a month and a half, they recorded sounds, also using three time-lapse cameras to collect images – including the "drop height" (how far the ice fell into the water) – so they could compare photos to the recordings. The team created a formula to represent the relationship between the size of a piece of ice falling from a glacier and the sound it makes underwater, also accounting for the pieces of ice falling from varying heights. (Hear an example of the sound an iceberg makes while calving <a href="https://soundcloud.com/user-248456662/iceberg-calving-hansbreen-glacier" target="_blank">here</a>.)</p>
Unlocking Information About Antarctic Ice Shelf<p>Other researchers also are using hydrophones to learn more about crumbling glaciers. Bob Dziak, research oceanographer with the NOAA/Pacific Marine Environmental Laboratory <a href="https://www.pmel.noaa.gov/acoustics" target="_blank">acoustics research group</a>, captured a massive calving event of the Nansen Ice Shelf in Antarctica with a hydrophone. He published the results with colleagues in <a href="https://www.frontiersin.org/articles/10.3389/feart.2019.00183/full" target="_blank">Frontiers in Earth Science</a></p><p>On April 7, 2016, satellite images showed a massive calving event had occurred on the ice shelf. The paper described it as the "first large scale calving event in >30 years."</p><p>However, once Dziak and colleagues delved into the data from three hydrophones deployed 60 kilometers east of the ice shelf, they uncovered a series of "icequakes" from January to early March 2016. He and other researchers believe that much of the ice actually broke free in mid-January to February, but it remained in the same location until an April storm – which their paper described as the "largest low-pressure storm recorded in the previous seven months" – broke the ice free.</p><p>"We suspected that the icebergs broke apart but remained in place – kind of pinned in place – until a major storm with high winds passed through the area and, finally, it was that last push that pushed the icebergs out to sea," Dziak says.</p><p>He and his co-authors wrote that "fortuitous timing and proximity of the hydrophone deployment presented a rare opportunity to study cryogenic signals and ocean ambient sounds of a large-scale ice shelf calving and iceberg formation event."</p>
Listening to Songs of Humpback Whales<p><a href="https://www.mbari.org/" target="_blank">Monterey Bay Aquarium Research Institute</a> studies the ocean, including its acoustics. One of the institute's projects involves examining the soundscape of California's Monterey Bay, including sounds from animals, humans, weather, and geologic processes like earthquakes. The researchers once even recorded an under-sea landslide. They also focus on recording and analyzing the <a href="http://www.mbari.org/humpback-song/" target="_blank">songs of humpback whales</a>. Male humpback whales' songs can be over 15 minutes in length, and they can be repeated for long periods of time – even hours. Listening to these songs and analyzing them can provide unique insights into the lives of these complex animals.</p><p>"Any time we want to study marine mammals, sound gives us a window into their lives because they use sound for all of their essential life activities, really," says institute biological oceanographer John Ryan. "Communication, foraging, reproduction, navigation – depending on the species, of course."</p><p>Previously, scientists had thought singing occurred only during courtship and mating, but now they think whales may also use song while migrating and hunting. They know song has a crucial role in the whales' lives.</p><p>"There's a whole other dimension to humpback whale song," Ryan says. "It is a mode of cultural transmission in this species. They learn songs from each other. They share songs as a population, and when populations mix and mingle, they learn new ideas, they explore with their song, improvise, and it's a real essential part of their culture."</p>
By William S. Lynn, Arian Wallach and Francisco J. Santiago-Ávila
A number of conservationists claim cats are a zombie apocalypse for biodiversity that need to be removed from the outdoors by "any means necessary" – coded language for shooting, trapping and poisoning. Various media outlets have portrayed cats as murderous superpredators. Australia has even declared an official "war" against cats.
Faulty Scientific Reasoning<p>In our <a href="https://doi.org/10.1111/cobi.13527" target="_blank">most recent publication</a> in the journal Conservation Biology, we examine an error of reasoning that props up the moral panic over cats.</p><p>Scientists do not simply collect data and analyze the results. They also establish a logical argument to explain what they observe. Thus, the reasoning behind a factual claim is equally important to the observations used to make that claim. And it is this reasoning about cats where claims about their threat to global biodiversity founder. In our analysis, we found it happens because many scientists take specific, local studies and overgeneralize those findings to the world at large.</p><p>Even when specific studies are good overall, projecting the combined "results" onto the world at large can cause unscientific overgeneralizations, particularly when <a href="https://doi.org/10.1016/j.tree.2015.01.003" target="_blank">ecological context is ignored</a>. It is akin to pulling a quote out of context and then assuming you understand its meaning.</p>
Ways Forward<p>So how might citizens and scientists chart a way forward to a more nuanced understanding of cat ecology and conservation?</p><p>First, those examining this issue on all sides can acknowledge that both the well-being of cats and the survival of threatened species are legitimate concerns.</p><p>Second, cats, like any other predator, affect their ecological communities. Whether that impact is good or bad is a complex value judgment, not a scientific fact.</p><p>Third, there is a need for a more rigorous approach to the study of cats. Such an approach must be mindful of the importance of ecological context and avoid the pitfalls of faulty reasoning. It also means resisting <a href="https://doi.org/10.1111/cobi.13126" target="_blank">the siren call of a silver (lethal) bullet</a>.</p>
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