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Response: Carbon dioxide removal (CDR)

CO2 converted to sold rock – image: CarbFix

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Carbon dioxide removal (CDR) ‘negative emissions technologies’

Summary

“In 2022, the world emitted 40.5 billion tonnes of CO2. At that rate, for every year of operation at its full potential, each CDR hub would take the atmosphere back in time by almost 13 minutes, but in the time it took to remove those 13 minutes of CO2, the world would have spewed another full year of CO2 into the atmosphere.

“If everyone on Earth planted a tree—8 billion trees—it would take us back in time by about 43 hours every year, once the trees had matured.

Humanity has never removed an atmospheric pollutant at a global, continental or, even, regional scale—we have only ever shut down the source and let nature do the clearing up.” Prof. David Ho, 2023

“Don’t Fall for Big Oil’s Carbon Capture Deceptions: Carbon capture technology is a PR fig leaf designed to help Big Oil delay the phaseout of fossil fuels.” – Scientific America, Dec. 2023

“Climate targets that depend heavily on CO2 removal may contravene international law” – Science, Nov. 2023

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Home > Climate wiki > Response > Negative emissions technology

Carbon dioxide removal (CDR) ‘negative emissions tech’

Summary

“In 2022, the world emitted 40.5 billion tonnes of CO2. At that rate, for every year of operation at its full potential, each CDR hub would take the atmosphere back in time by almost 13 minutes, but in the time it took to remove those 13 minutes of CO2, the world would have spewed another full year of CO2 into the atmosphere.

“If everyone on Earth planted a tree—8 billion trees—it would take us back in time by about 43 hours every year, once the trees had matured.

Humanity has never removed an atmospheric pollutant at a global, continental or, even, regional scale—we have only ever shut down the source and let nature do the clearing up.” Prof. David Ho, 2023

“Don’t Fall for Big Oil’s Carbon Capture Deceptions: Carbon capture technology is a PR fig leaf designed to help Big Oil delay the phaseout of fossil fuels.” – Scientific America, Dec. 2023

“Climate targets that depend heavily on CO2 removal may contravene international law” – Science, Nov. 2023

DACC: Direct Air Carbon Capture with Sequestration (permanent storage as rock underground)

Captures and stores carbon (negative emissions) by extracting CO2 from the atmosphere using renewable energy and converting it into solid rock (calcium carbonate) deep underground in basaltic rock within 2 years. Carbfix (Iceland, powered by geothermal energy which, unbeknown to most people, emits CO2) and Climeworks are the only joint companies currently doing this (Fig. 1 and Videos 1 and 2).

Four key hurdles:

1. The site in Iceland is on an active volcanic complex; sequestration is only ‘permanent’ until the next eruption. If the site is regarded as a proof-of-concept only, then:

2. Currently, the full carbon cost of construction and deployment at a scale vastly exceeds the amount of carbon being sequestered.

“The energy requirements for a net removal of ~ 3.3 gigatons of carbon equivalents by amine DAC “would amount to a global energy requirement of  29% of total global energy use in 2013 (540 EJ year−1)”, equal to nearly the total amount of electricity generated in the U.S. in 2017. Yet, even these amounts omit some downstream components of the DAC life cycle process, such as the energy requirements for transportation or sequestration of the captured CO2 and energy requirements for manufacturing sorbent at scale.” – Alice Friedemann |Quote from Joppa et al 2021

3. If CO2 can be stored underground near factories that use renewal energy but produce large amounts of CO2, then the cost of will become much more appealing. However, this requires mining suitable rock types. New Zealand has suitable rock formations…covered by native ecosystems.

4. Their scaled up ‘Mammoth’ project (2024) can eventually draw down 0.0000326Gt. That’s still only a fraction of current emissions (37.55Gt in 2023 alone). To scale up to meet just those annual emissions would require 1,151,840 additional fully operating plants of the same capacity. Immediately. But then we still need to withdraw all the excess emissions accumulated over the past 180-odd years.

Northern Lights has partnered with Climeworks to develop the same processes to store CO2 off the coast of Norway. Given the urgency of the climate problem, the company is developing the world’s first open-source CO2 transport and storage infrastructure to enable and encourage innovation and technology development in a fully transparent manner.

“The key is to identify the right place to inject and contain the CO2, which is trapped in microscopic rock pores by the same process that trapped oil and gas and natural CO2 for millions of years. Geologists look for a permeable rock formation that is stable and deep enough to ensure the CO2 is a dense fluid rather than a gas. Close monitoring, using seismic data, is used to refine theoretical models and check that the CO2 is moving within the rock space as expected (this is known as “plume migration”). In Snøhvit, for example, plume monitoring shows some of the CO2 trapped in rock spaces due to capillary forces, some dissolved in brine and some mineralised into rock.” – Northern Lights

Fig. 1: Carbfix stores carbon permanently underground. The process involves injecting carbonated water several thousand metres underground in basaltic rock formations, where it rapidly (less than 2 years) mineralises into solid rock (see image at the top of this page).
Video 1
Video 2: This video was filmed in 2016. Climeworks and Carbfix went from the laboratory in 2014, to complete proof of concept by 2016. It expanded to the ‘Mammoth’ project in 2024.
If the (full life-cycle) carbon emissions cost of DACs drops below the amount of carbon stored, then the technology becomes genuinely negative.

DAC: Direct Air Capture recycles CO2 back into the atmosphere

Removes carbon from the air using an exceptionally costly process, but instead of storing it, recycles it into more fuel, which goes straight back into the atmosphere. For example, Carbon Engineering in Squamish, Canada, which calls itself ‘air-to-fuel’ technology, is backed by one of the dirtiest types of fossil fuel developers on the planet: the oil sands in Alberta. This is not negative emissions technology. It’s reselling used fossils fuels, claiming them to be climate-friendly or even more disingenuously, ‘carbon-free’:

“Imagine driving up to your local gas station and being able to choose between regular, premium, or carbon-free gasoline.”        – National Geographic

While industries such as airlines and shipping are using DAC because there is yet no viable alternative to fossils fuels, some heavy fossil fuel industries use it as an excuse to continue business as usual, while claiming to be helping the planet (Video 3).

Video 3: 13-min. video explains DACS, which is definitely not carbon negative technology. It’s worth listening until the end, even though it verges into the politics of climate change, as it points out the truth behind the investors in DAC.

CCS: Carbon Capture and Storage underground (not the same as DACCS)

Factories and power generating plans capture the CO2 they emit before it goes into the atmosphere. They then have three options:

  1. 70% is currently injected into depleted oil wells to squeeze out the last few drops of oil, to keep us addicted to fossil fuels. This is called ‘Enhanced Oil Recovery’. Companies in the US enjoy massive tax breaks for ‘sequestering’ carbon this way. It’s the worst kind of greenwashing as it perpetuates oil addiction.
  2. Inject it into sedimentary rock formations and dry aquifers. Given their past assurances about the safety of their operations, this raises concerns about the potential for CO2 leaking out over the coming decades. Potential leakage notwithstanding, it still means taking more fossil fuels out of the ground and burning them, continuing fossil fuel addiction. Companies that claim to capture 100% of their CO2 do not make them ‘carbon neutral’ unless every aspect of their business offsets 100% of all carbon costs for the full life-cycle of every aspect of their business including the cost of the materials used to build structures, make products, transport them, capture all of those emissions as well, and guarantee storing the captured CO2 gas underground indefinitely.
  3. A tiny but growing percentage uses DACC to store it in suitable rock formations.

BECCS: Bioenergy with Carbon Capture and Storage (growing forests to burn them)

“We found that in a majority of the areas where forests will be replaced more carbon is stored by keeping the forests.” – Smolter and Ernsting

BECCs is favoured by the IPCC in its modelling. The process involves planting lots of fast growing plants such as radiata pine, cut them down, burn them for ‘bioenergy’, capture the CO2 and inject it underground and hope it stays there, or sell it for Enhanced Oil Recovery, burn that newly recovered oil, adding more CO2 into the atmosphere, grow more radiata pine…repeat.

Despite the fact that Enhanced Oil Recovery leads to the recovery and burning of potentially vast quantities of fossil fuels which would otherwise have remained under the ground, use of CO2 for this purpose is classed as a form of CCS, a claim accepted even by the Intergovernmental Panel on Climate Change. ” – Smolter and Ernsting

For BECCS to work, it would mean replacing much of the existing native forest on the planet with fast growing trees, destroying irreplaceable, life-supporting ecosystem services and releasing carbon locked up in those forests and their soils. Additionally, by 2100 BECCs would also need to use around 25-46% of the land currently used to feed people (Video 4). While New Zealand may find ways to avoid some of these problems, the same cannot be said for developing nations keen to cash in other nations’ (including New Zealand’s) need to purchase carbon offsets in order to meet obligations under the Paris Agreement. To understand how flawed BECCs is, see this timeline.

Bioenergy with carbon capture and storage is expected to capture, on average, around 130 billion tonnes of carbon via planting crops for biofuel that are then burnt in power stations…. It is expected that an additional area of one or two times the size of India is needed for bioenergy crops by 2050.” –  Dr Anna Harper, University of Exeter.

Video 4: BECCS: the not-so good, the bad, and the really really bad.

My colleagues and I find that expansion of bioenergy in order to meet the 1.5C limit could cause net losses in carbon from the land surface. Instead, we find that protecting and expanding forests could be more effective options for meeting the Paris Agreement. ” – Dr Anna Harper, University of Exeter

Dumping plant and forestry waste into the ocean

Ignoring the CO2 costs of collecting and transporting forestry slash and other agricultural waste, the idea is to ship the material offshore and dump it into oceanic dead zones. There is little to no oxygen in these dead zones and hence very little if any life can exists, so the material won’t rot, and therefore won’t release CO2

As we are creating an ever-growing number and scale of lifeless oceanic dead zones in part due to toxic runoff, increasing ocean heating and acidification, several companies in the US are now viewing dead zones as resources to dump plant waste and sell the carbon credits.

Sunk terrestrial biomass doesn’t steal nutrients from marine life, removing it from land could deplete soil of nutrients. ‘Over time we’re going to also be losing some of the fertility that crops and forests need.’ ” – Science News December, 2023

Fig. 2: Running Tide is using wood from forestry that would otherwise be burned or left to decay to create floating ‘buoys’ seeded with seaweed. The buoys are released off Iceland, where ocean currents carry them over a deep region with little oxygen. Eventually they become waterlogged and sink, along with any seaweed that has grown en route. Image: Jennifer Johnson

Bioenergy from burning slash with CO2 pumped into greenhouses

Uses heat by burning the slash from radiata pine and other waste plants, then pump the emitted CO2 into  greenhouses to increase plant growth. Seem like a good idea, however, while plants exposed to higher levels of CO2 may grow faster, their nutritional values are declining (Video 5) and they are structurally weaker. This may limit the use of this process to growing short-lived non-edible products like flowers. (Overall, global vegetation growth is declining, in spite of the so called CO2 fertilisation effect’).

Hot Lime Labs in New Zealand uses this process. So does Climeworks in Switzerland, although they capture the CO2 from DAC, not from burning biomass. Further research is strongly recommended to assess the nutritional value of food grown using this method.

Video 5: What’s causing our food to become less nutritious?

Carbon captured and stored in concrete

  • For every metric tonne of cement produced, one metric tonne of CO2 goes up into the atmosphere
  • The world uses 4 billion tonnes of concrete every year
  • Fossil fuels like powdered coal are required to melt limestone, resulting in a more CO2 emissions
  • The cement industry accounts for 8% of total greenhouse gas emissions

Several companies are now finding ways to permanently store CO2 in concrete. Not all are ‘carbon-negative’ as claimed, however the processes are innovative and look promising. See:

  • Carbon Cure uses CO2 from industrial emitters
  • Carbicrete uses mineral waste and CO2 as raw materials
  • Blue Planet uses CO2 as raw material for making carbonate rocks
  • Solidia produces cement at lower temperature, ie reduces emission
Video 6: Carbon capture in concrete

Use algae to grow your own cement

Biomason uses a natural non-modified non-pathogenic bacteria to grow biocement® building material without heat, using a process similar to hydroponics. The species used is commonly found in natural environments across the world.

It takes around 72 hours for Biomason’s tiles to reach full cure strength (traditional concrete can take up to 28 days to cure) and the product is 3 x stronger than concrete (Video 7).

In marine environments, self-sustaining natural marine microorganisms that source nutrients from seawater, are used to propagate calcium carbonate precipitation (similar to how beach rock is formed, but over much short time frames). The result is the sustained structural integrity of products with self-healing abilities. This process can be used to quickly build breakwaters and other ‘hard’ coastal/marine structures.

See: ‘Tiny algae could help fix concrete’s dirty little climate secret – 4 innovative ways to clean up this notoriously hard to decarbonize industry.’ – The Conversation, Sept. 2022 (Video 8)

Video 7: Growing bricks using hydroponics
Video 8: Laying the foundation for the future of carbon-zero buildings

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