[Closed] [Cycle 3] Utilising By-products from Carbon Capture | PUB, Singapore’s National Water Agency

How might we make the most effective use of the calcium carbonates and magnesium hydroxides/ carbonates formed through the capture of carbon dioxide (CO₂) in seawater in the most beneficial and economically viable way?

Challenge Owner

Water Supply (Plants) Department

In line with Singapore public sector’s target, PUB aims to achieve net zero emissions around 2045. PUB’s decarbonisation strategies are to:

Replace carbon-emitting fuels with renewables,
Reduce carbon emissions by improving efficiency and reducing water demand, and
Remove carbon from the environment through technologies that can be integrated with PUB’s operations.

Under the strategy to remove carbon, PUB is exploring with partners on technologies to capture CO₂ in seawater and locking it in calcium carbonate and magnesium hydroxide/magnesium carbonate precipitates that form as by-products. Besides permanently storing carbon dioxide, these carbonate and hydroxide precipitates could potentially have valuable industrial applications such as base materials for cement and concrete production, cosmetics, paints and many others.

Seawater contains about 0.4kg of calcium and 1.3kg of magnesium per cubic meter. Hence 1kg of calcium carbonate and 3.2kg of magnesium hydroxide or 4.6kg of magnesium carbonate per m3 of seawater could potentially be produced from such mineralisation processes. Large quantities of calcium carbonates and magnesium hydroxides/carbonates will potentially be available if technologies for CO2 capture with seawater are successfully employed with desalination. These materials are valuable resources that can be recovered for industrial and commercial use.

We are interested in seeking partners to work with who can identify and demonstrate how the calcium carbonates and magnesium hydroxides/carbonates can be used either directly or repurposed for applications in industry that offer the most economical and environment-friendly utilisation, especially in Singapore’s context. We are seeking to support solutions that will be able to demonstrate through lab scale or pilot trials, the utilisation of these by-products.

The calcium carbonates and magnesium hydroxides/carbonates from the CO2 capture and removal technologies that PUB is currently exploring are recovered from the process by sedimentation and are in the form of slurry, which may have anywhere from 50 to 99% saline water content.
The slurry may contain other minerals and precipitates that occur naturally in seawater or are formed during the CO2 capture and removal process. This needs to be verified as part of the proposed solution for this challenge. Additional treatment processes may be required to achieve the necessary purity for the proposed application.
Treatment of the slurry may be required to facilitate transportation of the resource to the point of use.
Regulatory requirements and standards related to the proposed application shall be complied with.
Applications for magnesium hydroxide shall enable the magnesium hydroxide to capture CO2 permanently while it is used.
The proposed application shall not compromise the permanence of the CO2 captured in the calcium and magnesium carbonates.

A proof-of-concept in the form of a lab-scale or pilot trial to apply the recovered materials in the proposed application and demonstrate its feasibility and techno-economics. In addition, innovators in their applications should provide details on:

Technical merits of the proposed application,
How the calcium carbonate and magnesium hydroxide slurries might be utilised either directly or repurposed before they could be used.
An assessment of the quantity and purity of calcium carbonates and magnesium hydroxides/carbonates
Total system techno-economics should be inclusive of transportation to point of use, additional treatment processes and other considerations should be included.

If the proof-of-concept is successful, the solution will be developed further and considered for implementation with the partner.

Challenge Owner

Water Supply (Plants) Department

In line with Singapore public sector’s target, PUB aims to achieve net zero emissions around 2045. PUB’s decarbonisation strategies are to:

Replace carbon-emitting fuels with renewables,
Reduce carbon emissions by improving efficiency and reducing water demand, and
Remove carbon from the environment through technologies that can be integrated with PUB’s operations.

The calcium carbonates and magnesium hydroxides/carbonates from the CO2 capture and removal technologies that PUB is currently exploring are recovered from the process by sedimentation and are in the form of slurry, which may have anywhere from 50 to 99% saline water content.
The slurry may contain other minerals and precipitates that occur naturally in seawater or are formed during the CO2 capture and removal process. This needs to be verified as part of the proposed solution for this challenge. Additional treatment processes may be required to achieve the necessary purity for the proposed application.
Treatment of the slurry may be required to facilitate transportation of the resource to the point of use.
Regulatory requirements and standards related to the proposed application shall be complied with.
Applications for magnesium hydroxide shall enable the magnesium hydroxide to capture CO2 permanently while it is used.
The proposed application shall not compromise the permanence of the CO2 captured in the calcium and magnesium carbonates.

Technical merits of the proposed application,
How the calcium carbonate and magnesium hydroxide slurries might be utilised either directly or repurposed before they could be used.
An assessment of the quantity and purity of calcium carbonates and magnesium hydroxides/carbonates
Total system techno-economics should be inclusive of transportation to point of use, additional treatment processes and other considerations should be included.

If the proof-of-concept is successful, the solution will be developed further and considered for implementation with the partner.

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Utilising By-products from Carbon Capture

Challenge Statement

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