Expectations for new 'A-ERW' weathering technology developed by Waseda University, Mitsubishi Heavy Industries Ltd. and others

The 'Advanced enhanced rock weathering (A-ERW) technology actively combined with site characteristics' project has been selected for Goal 4: Realization of sustainable resource circulation to recover the global environment by 2050 of NEDO 's Moonshot Research & Development Program. It is hoped that this will serve as a new trial for NETs (Negative Emission Technologies). Researchers are now focused on these as technologies that could speed up the absorption and fixation of CO₂ by adding artificial processes to the natural process of absorbing and fixing atmospheric CO₂. This has been proposed by a research group with members from Mitsubishi Heavy Industries Engineering, Hokkaido University and Kyoto Prefectural University, with Professor Takao Nakagaki of Waseda University serving as Project Manager (PM).

To achieve carbon neutrality, it is necessary to either avoid the diffusion of CO₂ into the atmosphere or to offset it by some means. In addition, to stabilize the climate, it is necessary to ensure the absorption and fixation of the atmospheric CO₂ that has been emitted in the past; the focus is on NETs as the technology to achieve this.

The subject of the project is ERW (Enhanced Rock Weathering) technology to promote weathering, which absorbs atmospheric CO₂ and encourages mineralization using natural rocks. In the past, ERW has mainly worked on the assumption of smashing only basalt and scattering this on cultivated land. However, it takes time for the atmospheric CO₂ dissolved in rainwater to react with the scattered rock; the net fixation quantity is not high, and it has yielded little data useful for carbon accounting, which serves as actual evidence.

With this in mind the project has decided to rethink ERW as 'expanding relative physical surface area (physical weathering)' × 'CO₂ mineralization via mass transport and chemical reactions', and to apply methods to accelerate each of these processes with as little extra energy as possible.

When it comes to scattering on cultivated land, the project will increase the tangible fixation quantity by combining cultivation methods and management methods adapted to the soil. It will also ensure there is data on areas such as the CO₂ mineralization potential of each rock; the pretreatment energy needed to excavate, transport, crack and powder natural rock; the CO₂ mineralization speed of each scattering method and the mineralization rate after a certain time has passed, based on experimental data and the advanced predictions of a numerical calculation model.

On top of this, the project will confirm the validity of prediction models by developing an efficient monitoring method and carrying out experiments in actual environmental conditions, accumulate the data obtained and develop a template for information infrastructure as evidence for carbon accounting LCA.

For A-ERW, the group has selected Hokkaido as a model region as there is plentiful geological survey data. This will be a NET that involves the effective smashing of rock suited to A-ERW, obtained from different areas, the promotion of weathering via methods suited to the land, and the removal of atmospheric CO₂, at the same time as ensuring resource recycling and yielding co-benefits for the region.

The aim is also to demonstrate simple and highly accurate carbon accounting LCA in Japan and overseas to obtain international consensus, while working toward quick social implementation through CO₂ reduction credits.

PM Nakagaki commented, 'If we can clarify carbon accounting with a scientific basis and obtain international consensus, it will be possible to turn this into a business through these credits. In addition to ensuring the co-benefits of A-ERW and enriching local areas, we hope to contribute to the fixation of gigatons (billions of tons) of CO₂.'