Professor Zhang Dongxiao, Dean of Peking University Institute of Ocean Research and College of Engineering, published a paper in Science Advances on July 4, and introduced the lasted achievements in the carbon sequestration in deep-sea sediments.

The first author of this paper is Teng Yihua, a doctoral student jointly trained by College of Engineering and Institute of Ocean Research, Peking University.

Carbon capture and storage is considered as a promising option to stabilize the atmospheric concentration of anthropogenic CO2 and mitigate climate change. Conventional proposals for geologic sequestration, including injection into deep saline aquifers, oil and gas fields, and deep coal seams, are prospective, but the stored supercritical CO2 is buoyant and consequently may escape via permeable pathways into the atmosphere. Sequestration of carbon dioxide in deep-sea sediments has been proposed for the long-term storage of anthropogenic CO2 that can take advantage of the current offshore infrastructure.

With a detailed study of the coupled processes, Professor Dongxiao Zhang's research group investigate whether storing CO2 into deep-sea sediments is viable, efficient, and secure over the long term. Also, they study the evolution of multiphase and multicomponent flow and the impact of hydrate formation on storage efficiency.

The results show that low buoyancy and high viscosity slow down the ascending plume and the forming of the hydrate cap effectively reduces permeability and finally becomes an impermeable seal, thus limiting the movement of CO2 toward the seafloor. The study find that under a deep-sea setting, CO2 sequestration in intact marine sediments is generally safe and permanent.

This study provides a new solution for carbon sequestration besides land, and expands the burial site to a wide range of marine sediments. It has important significance and application prospects for future global carbon dioxide emission reduction and storage selection .

The operation facilities required for deep-sea geological storage are similar to the semi-submersible offshore platforms used in the exploitation of natural gas hydrates (combustible ice) in the sea, professor Zhang said, maybe we will seek opportunities to combine field experiments with combustible ice mining.

Schematic of long-term viability of carbon sequestration in deep-sea sediments