Quantifying the true carbon removal potential of enhanced rock weathering
Lead Research Organisation:
Imperial College London
Department Name: Civil & Environmental Engineering
Abstract
To achieve the UN goal of less than 2 degrees of global warming, we need to not only reduce carbon emissions, but actively remove part of the carbon dioxide (CO2) we have added to the atmosphere. For this reason, the UK has committed to actively remove ~50 million tons of CO2 by 2050.
While multiple solutions have been proposed to achieve this, only a handful can be applied at scales large enough to meaningfully contribute to climate mitigation. One of those solutions is the acceleration of silicate rock weathering (also called Enhanced Rock Weathering - ERW), which theoretically could globally remove ~10% of our annual carbon emissions. CO2 dissolves in water and then reacts with silicate rocks. The weathering products are then transported through streams and rivers to the ocean, where the carbon is locked away for thousands of years. This reaction actively removes carbon from the atmosphere, and at the same time it releases minerals that can benefit plants. In nature the process is very slow but can be sped up by simply crushing those rocks into a fine dust, which could be distributed by existing farming equipment at global scales.
Despite the promise of ERW for climate mitigation, there are very few large-scale experiments which have demonstrated its efficacy, and non-target effects of rock dust on soils and fresh waters are not well known. In fact, all the weathering products, as they are transported via water in the soils and in the rivers, can interact with the soil itself, with plants, and with microorganisms living in soils and river water. This interaction may reduce the efficiency of ERW by orders of magnitude, casting doubt on its implementation as a global negative emission technology. Moreover, organisms at the basis of land and water food webs - plants and microbes - may be impacted by the side effects of ERW application. However, we lack the necessary interdisciplinary knowledge from soil and aquatic biogeochemistry, ecology and hydrology to fully understand and predict the efficiency of ERW. In this project we assemble a team of experts from all the aforementioned scientific disciplines to provide a complete understanding of the process of ERW, from the application of silicate rock dust until the weathering products reach the oceans.
To achieve that, we will combine interdisciplinary experimental techniques, state of the art research infrastructure, and computational modelling. First, we will provide new fundamental knowledge on how the rock weathering process and the different weathering products affect and are affected by plants and soil microbes. An experiment that will disentangle the impacts of soils, plants and microbes will be conducted at Imperial College London. Then, we will provide fundamental knowledge on how the weathering products interact with river waters and the microorganisms living in them. To do that an experiment that disentangles the effects of river water chemistry, river flow dynamics, and aquatic microorganisms will be conducted at state-of-the art research facilities at the University of Birmingham. We will then generalize the new knowledge from the laboratory to the real world, by performing a full-scale field trial of ERW and monitoring all aspects of its efficiency in a Welsh forest. Finally, we will integrate all the new knowledge into an advanced ecohydrological model that can be used to predict the carbon removal efficiency at the catchment scale.
The final deliverable of the project will be an assessment of ERW's potential to remove CO2 in the UK, and whether it can significantly contribute towards the country's climate goals, and tools that can be used by stakeholders to credibly assess the carbon removal efficiency of ERW. This will be an essential resource for state decision makers, in charge of meeting a county's negative emission goals, and the carbon industry.
While multiple solutions have been proposed to achieve this, only a handful can be applied at scales large enough to meaningfully contribute to climate mitigation. One of those solutions is the acceleration of silicate rock weathering (also called Enhanced Rock Weathering - ERW), which theoretically could globally remove ~10% of our annual carbon emissions. CO2 dissolves in water and then reacts with silicate rocks. The weathering products are then transported through streams and rivers to the ocean, where the carbon is locked away for thousands of years. This reaction actively removes carbon from the atmosphere, and at the same time it releases minerals that can benefit plants. In nature the process is very slow but can be sped up by simply crushing those rocks into a fine dust, which could be distributed by existing farming equipment at global scales.
Despite the promise of ERW for climate mitigation, there are very few large-scale experiments which have demonstrated its efficacy, and non-target effects of rock dust on soils and fresh waters are not well known. In fact, all the weathering products, as they are transported via water in the soils and in the rivers, can interact with the soil itself, with plants, and with microorganisms living in soils and river water. This interaction may reduce the efficiency of ERW by orders of magnitude, casting doubt on its implementation as a global negative emission technology. Moreover, organisms at the basis of land and water food webs - plants and microbes - may be impacted by the side effects of ERW application. However, we lack the necessary interdisciplinary knowledge from soil and aquatic biogeochemistry, ecology and hydrology to fully understand and predict the efficiency of ERW. In this project we assemble a team of experts from all the aforementioned scientific disciplines to provide a complete understanding of the process of ERW, from the application of silicate rock dust until the weathering products reach the oceans.
To achieve that, we will combine interdisciplinary experimental techniques, state of the art research infrastructure, and computational modelling. First, we will provide new fundamental knowledge on how the rock weathering process and the different weathering products affect and are affected by plants and soil microbes. An experiment that will disentangle the impacts of soils, plants and microbes will be conducted at Imperial College London. Then, we will provide fundamental knowledge on how the weathering products interact with river waters and the microorganisms living in them. To do that an experiment that disentangles the effects of river water chemistry, river flow dynamics, and aquatic microorganisms will be conducted at state-of-the art research facilities at the University of Birmingham. We will then generalize the new knowledge from the laboratory to the real world, by performing a full-scale field trial of ERW and monitoring all aspects of its efficiency in a Welsh forest. Finally, we will integrate all the new knowledge into an advanced ecohydrological model that can be used to predict the carbon removal efficiency at the catchment scale.
The final deliverable of the project will be an assessment of ERW's potential to remove CO2 in the UK, and whether it can significantly contribute towards the country's climate goals, and tools that can be used by stakeholders to credibly assess the carbon removal efficiency of ERW. This will be an essential resource for state decision makers, in charge of meeting a county's negative emission goals, and the carbon industry.
