Science and Innovation

To limit global warming to below the 2 °C agreed in the UN Paris Agreement, projections indicate that both rapid decarbonisation and the implementation of negative emission technologies (NETs) will be necessary. It is therefore urgent to identify safe and scalable NETs that actively remove carbon dioxide from the atmosphere and ensure stable long-term carbon storage. In this respect, enhanced silicate weathering (ESW) is in the scientific spotlight as a NET in the field of agroecology. On a geological scale, silicate weathering captures 1.1 Gt of carbon dioxide annually, when the rock reacts in contact with atmospheric carbon dioxide and water, releasing bicarbonates that will either react with soil cations and precipitate as pedogenic carbonates or be drained into groundwater and reach the sea, thus decreasing ocean acidification. In this sense, ESW proposes to grind rocks into dust, increasing their reaction surface and accelerating the process. The application of these fine particles in agricultural fields has been proposed as an effective form of carbon sequestration, as it does not compete with agricultural production in terms of surface area, while offering multiple benefits for vegetation. The rapid dissolution of silicates favours biomass production due to increased: (i) soil alkalinity, (ii) soil cation exchange capacity (CEC), (iii) soil nutrients from silicate weathering products (e.g. Ca, Mg, K) or consequent changes in soil pH (e.g. P, Al, Fe), and (iv) resistance to pests and drought due to higher silicon (Si) content in plant tissues. It is estimated that 70% of carbon dioxide emissions come from cities, occupying only 3% of the earth's land surface. Thus, the application of ESW in urban parks and gardens presents a unique opportunity to increase carbon dioxide sequestration within urban areas themselves, while at the same time it can support the growth of lush, drought and pest resistant vegetation (grasses, shrubs and flowers) in the context of current climate change.