Climate warming is progressively issuing a severe warning to humanity through its multifaceted and immense threats.

In summary, we will artificially construct an accelerated mineralization rate system, emulating coccolithophores, to achieve an autotrophic carbon sequestration system. This approach aims to fundamentally address the climate crisis.

NASA has published articles titled "This Summer is the Hottest on Record" for two consecutive years. The temperature data over these two years clearly indicates that summer temperatures have risen significantly, along with an extension of the duration of high temperatures. This phenomenon is attributed to anthropogenic greenhouse gas emissions ^{[1] [2]} .

The occurrence of the "hottest summer" in 2023 and 2024 may not be an isolated phenomenon. Analysis of NASA's statistics on average temperatures in the Northern and Southern Hemispheres, as well as seasonal temperature variations across different years, indicates a long-term trend of global warming ^[3] .

The data on greenhouse gas emissions over the years, as reported in the Emissions Gap Report 2020, shows that carbon dioxide (CO₂) is the greenhouse gas most closely linked to human activities and the one most urgently in need of addressing ^[4] .

Carbon dioxide has already become a significant safety hazard that will pose a long-term threat to the security of human society. Countries around the world have actively reached a consensus to address this issue, aiming to achieve the goal of limiting temperature rise to within 1.5°C by 2030 ^[5] .

To achieve this goal, humans are striving in all aspects. New environmental policies are continuously being tested, carbon trading markets are gradually emerging, carbon capture technologies are constantly evolving, and environmental awareness is being instilled in the next generation. Our beautiful blue planet stands as a witness to our relentless efforts to solve the climate crisis.

To achieve efficient carbon capture and long-term carbon sequestration, after extensive literature research and discussions with experts during our Human Practices activities, we have ultimately decided on a project plan that focuses on the ocean—the largest natural carbon reservoir—as the setting for carbon capture, and carbon sequestration in the form of carbonate minerals within the lithosphere, the layer where carbon can be stored for the longest duration.

Considering the issue of ocean acidification, inspired by the Exete iGEM 2020 team , we adopted a strategy to increase the consumption of carbon dioxide in seawater to address acidification. By using carbonic anhydrase (CA), we aim to convert gaseous CO₂ into bicarbonate ions, thereby increasing the concentration of bicarbonate in the microenvironment.

However, if the elevated bicarbonate concentration is not properly managed, the ocean could become even more acidic, exacerbating the problem.To address this issue, another protein, CARPs, was employed to promote the consumption of bicarbonate. CARPs are derived from reef-building corals and work by lowering the pKa value of calcium carbonate (CaCO₃) in their acidic-rich regions, facilitating the formation of aragonite ^[6] . Although the biomineralization mechanisms of various CARP proteins are not yet fully understood, CARP1, CARP2, and CARP3 are secretory proteins that have a higher potential to form calcium carbonate minerals in seawater systems.

To explore this idea, we designed an experimental plan that focuses on two key aspects: increasing bicarbonate concentration and reducing calcium carbonate solubility. By doing so, we aim to enhance a physically-mediated pump to promote calcium carbonate precipitation, facilitating carbon sequestration.

However, this method of carbon absorption remains quite limited. During our research, the modeling team provided valuable insights, revealing that the distribution of organic carbon in the ocean is also significant. After brainstorming, we realized that while the flux of organic carbon in seawater is enormous, the challenge lies in the fact that nearly all organic carbon is cycled through the ocean’s biological carbon pump and eventually reverts back into carbon dioxide ^[7] .

We decided to increase the carbon sink flux through the co-precipitation of organic and inorganic materials, aiming to sequester both inorganic carbon minerals and organic carbon simultaneously.

Our focus shifted to chitin—the most abundant renewable polymer in the ocean—as the key organic material for this process. By leveraging chitin's natural abundance and properties, we aim to promote the co-precipitation of carbon, facilitating more efficient carbon sequestration ^[8] .

By designing proteins that can simultaneously incorporate chitin and calcium carbonate minerals, we aim to achieve the co-precipitation of calcium carbonate and chitin. This approach leverages the ocean's gravitational carbon pump, allowing more inert organic materials from the biological carbon pump to enter the anoxic environments of the deep sea. This process helps slow down the degradation of organic matter, resulting in the formation of long-term organic-inorganic carbon sequestration.

We established a co-culture system with the three strains to efficiently promote calcium carbonate precipitation and reduce atmospheric carbon dioxide concentrations, all while ensuring bio-safety to address the climate crisis. To support the experimental team in realizing and refining this plan, significant efforts have been made in hardware development, modeling, and integrated human practices (IHP) work. This collaboration from multiple angles ensures that the project proceeds safely and effectively.