Promoting ocean calcifiers to sequester atmospheric carbon

Oceans & marine

The oceans are the largest carbon sink for atmospheric carbon and have taken up over 30% of anthropogenic emissions. Carbon uptake occurs abiotically through processes such as ocean-atmosphere interaction and weathering processes. Biotic processes play an important role in oceanic carbon uptake too, with most attention going to carbon-consuming photosynthesising organisms.

Moore et al. (2023) argue that the potential role of shellfish and other calcifiers in carbon sequestration is significantly overlooked in the CDR literature. The authors suggest that calcifier production should be encouraged, because the production of their shells would be able to remove ‘significant amounts of CO2 … from the atmosphere with much greater permanence and less cost than any other solution can offer.’

Technological Readiness Level (TRL)

Medium 2

Mussel farms are already in existence. Such farms are however not used for carbon sequestration, and it is therefore unclear if a scaling up or alteration would have the desired effects.

Technological Readiness Level (TRL)

A technology with a TRL of 4-6: TRL 4 – validated in lab; TRL 5 – validated in relevant environment; TRL 6 – demonstrated in relevant environment

Scalability

Medium 2

Moore et al (2022) and Moore et al (2023) write that it would be relatively straightforward to expand current farms to a sufficiently large scale and that ‘[a] million mussel farms would permanently remove about 4.5% of the global CO2 emissions in each year’. However, this measure is untested and only described in these two articles.

Scalability

Physically somewhat scalable; linear efficiency

Timeliness for near-future effects

High 3

Timeliness for near-future effects

Implemented in time to make a significant difference

Northern + Arctic potential

Low 1

Mussels grow slower at colder temperatures.

Northern + Arctic potential

No noticeable extra positive effect beyond the global average; technology is unsuited to the Arctic

Global potential

Medium 2

Moore et al (2022) state that aquaculture captures ‘4.84 million tonnes of CO2 per year’, and that farms ‘designed to produce 10,000 tonnes of mussels per year would permanently remove from the atmosphere an annual total of 1,606 metric tonnes of CO2.' They therefore argue that ‘[a] million mussel farms would permanently remove about 4.5% of the global CO2 emissions in each year’. It is however hard to say how accurate such estimates are for the real world potential of this measure.///Moore et al (2023) furthermore argue that this would be a permanent sequestration, in contrast to measures like afforestation which could see significant amounts of carbon re-released into the atmosphere when trees die.

Global potential

Statistically detectable impacts

Cost - benefit

Low 3

Mussel farms would have the benefit of producing food, in contrast to other CDR technologies that would merely remove carbon from the atmosphere, and could thereby potentially be cheaper to run.

Cost - benefit

Low investment cost compared to the avoided damage cost (e.g., a few %) and/or inexpensive relative to other measures with similar impact

Environmental risks

Medium 2

Large scale cultivation could have an impact on local ecosystems.

Environmental risks

More widespread and possibly regional impacts that extend beyond the immediate solution deployment location

Community impacts

Beneficial 3

Such farms could potentially provide seafood and work for local communities.

Community impacts

Significant benefits to communities

Ease of reversibility

Easy 3

Ease of reversibility

Easily reversible naturally

Risk of termination shock

Low 3

Risk of termination shock

Low or insignificant termination shock or damage

Legality/governance

High 3

Legality/governance

Currently legal to deploy, with governance structures in place to facilitate it and/or financial incentives to develop it

Scientific/media attention

Low 1

Apart from the papers cited above, there seems to be so far little attention for this measure.

Scientific/media attention

Very low attention from individuals and/or abandoned ideas; low media attention; no commercial interest.

References

Moore, D., Heilweck, M., & Fears, W. B. (2023). Potential of ocean calcifiers to sequester atmospheric carbon in quantity and even reverse climate change. J Fish Res. 7 (1): 132. https://doi.org/DOI:10.35841/aajfr-7.1.132

Moore, D., Heilweck, M. (2022). Aquaculture: Prehistoric to Traditional to Modern. In: Aquaculture: Ocean Blue Carbon Meets UN-SDGS. Sustainable Development Goals Series. Springer, Cham. https://doi.org/10.1007/978-3-030-94846-7_3

Related ideas

Industry

Black carbon reduction

Black Carbon (BC), also known as soot, is produced through the incomplete combustion of fossil fuels and biomaterials. Apart from its negative health impacts, BC also has significant climate effects because it generally has a lower albedo than its surroundings, which increases the amount of radiation absorbed both when BC is present in the atmosphere and when it is deposited on land (Stjern et al. 2017). Due to the large albedo differences, the effects of BC are especially significant in areas that are normally covered in snow or ice (Hadley and Kirchstetter 2012; Sand et al. 2016; Kang et al. 2020).

Industry

Built-environment albedo enhancement (white roofs etc.)

An increase in GHGs in the atmosphere leads to a greater amount of outgoing infrared radiation from the earth being retained. There are several SRM ideas that seek to compensate for this by reflecting more radiation back to space.

River Ölfusá just North of Selfoss, South Iceland

Oceans & marine

River Liming

The pH of water is lowered when it takes up atmospheric carbon. Given that the Earth’s oceans serve as a major carbon sink, there is increasing interest in the possibility to artificially increase the alkalinity of water to restore pH to previous levels, and/or increase carbon uptake potential.

Clouds over Setesdalsheia, Norway, October 2013

Atmosphere / solar radiation

Cirrus cloud thinning

Cirrus clouds are high altitude ice clouds. They influence the Earth’s radiation budget as they reflect both incoming and outgoing radiation. However, they ultimately have a warming effect as they are more efficient at trapping outgoing longwave radiation (Kärcher 2017).

Coastal Archipelago Park of the South Coast ("Sørlandet") of Norway, colors at the shoreline (1)

Oceans & marine

Artificial downwelling

Oceans play an important role in global heat transfer and carbon storage processes. As global temperatures and atmospheric carbon levels rise, some have suggested artificially modifying the vertical movement of water to enhance these processes.

Ice sheets and glaciers

Pumping water onto ice sheets

One of the potentially most catastrophic effects of contemporary global warming would be the dramatic increase in sea levels as a result of the melting Greenland and Antarctic ice sheets. Even if all current emissions were immediately stopped, sea level rise could still occur because of locked-in warming (ICCI 2022).

Melting glacier ice, Rødefjord, Northeast Greenland National Park

Ice sheets and glaciers

Glacier insulation with fabrics

Up to 50% of the world’s glaciers are set to disappear this century, with many more at risk if emission reduction targets are not met (Rounce et al. 2023).

Blue Iceberg, Rødefjord, Northeast Greenland National Park

Sea ice & icebergs

Modular iceberg creation by submersibles

Arctic sea ice extent has rapidly decreased over the last few decades, with most multi-year ice disappearing altogether. This has already had major effects on local communities and ecosystems. The disappearance of the relatively reflective sea ice also leads to a dramatic decrease of albedo in the Arctic and subsequent high energy uptakes by the darker water during the Arctic summers.