ERW23

Tuesday 26 Sept 2023, 08:00 → 23:20 Europe/London

G.04 (University of Edinburgh - Edinburgh Climate Change Institute)

Lily Chaidamli (UNDO Carbon), Mia Shepherd, XinRan Liu (University of Edinburgh), Yanyan Gao (University of Edinburgh)

Unite with global scientists and academics at the 2023 International Conference on Enhanced Rock Weathering (ERW) in Edinburgh, United Kingdom. 

The first conference dedicated to ERW will be held at the prestigious University of Edinburgh on Tuesday, the 26th of September, 2023. We warmly invite scientists worldwide to come together to discuss the potentials and breakthroughs of ERW. The inaugural conference hopes to encourage international collaborations and drive further advanced Research & Development, to overcome existing scientific barriers. 

The programme features thought-provoking plenary sessions, that will promote knowledge exchange and inspire fresh perspectives.  We particularly want participation of early-career scientists, post-graduate students, and postdocs, who are poised to contribute significantly to the future of this field. 

This event is hosted by the Edinburgh Climate Change Institute (ECCI), a part of the University of Edinburgh and planned by a dedicated UK-based organising committee from UNDO Carbon. 

Join us to explore the cutting-edge science of ERW and shape its future. 

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Registration: 

Please register for the event by clicking on this link. 

08:15 Registration

Conference registration + tea and coffee

1 Welcome from XinRan Liu, Head of Science and Research at UNDO

Plenary: Session 1 - ERW Current And Future Roadmap

Convener: XinRan Liu (University of Edinburgh)

2 Transforming global agriculture for CO2 removal and increased production with crushed rock

Speaker: Prof. David Beerling (University of Sheffield)

3 Applied Innovation in Terrestrial Enhanced Weathering

Advancing terrestrial enhanced weathering as a climate mitigation strategy will require addressing open questions on technical readiness, environmental concerns and deployment strategies. While related lab and pilot scale research are progressing, there is still a large gap between the current state of terrestrial enhanced weathering activity, and that required for megaton or gigaton scale carbon removal. Here we present a technical roadmap focused on the research, development and deployment necessary to support the development of a robust terrestrial enhanced weathering industry, through an assessment of risks against long term goals, as well as critical pathways to technical viability and commercial scale deployment.

Speaker: Cara Maesano (RMI)

4 Computational Challenges in Enhanced Rock Weathering and Carbon Dioxide Removal Modelling at national Scales

The Leverhulme Centre for Climate Change Mitigation (LC3M) has been at the forefront of research into enhanced rock weathering (ERW) as a potential means of removing atmospheric CO2. Apart from laboratory studies and large-scale field trials, we undertake modelling studies aimed at assessing the feasibility, cost and CDR potential of ERW at national scales. These modelling efforts entail the use of a computationally intensive 1-D weathering model applied across a fine spatial grid, incorporating various climatic and economic drivers.
When addressing ERW on a national scales, numerous intricate factors come into play. These include the logistical challenges of transporting rock from its source to croplands, the variability in basalt minerology depending on its origin, and the demands on the electricity network required for rock grinding. Furthermore, the optimization routines we employ to determine the optimal pairings between rock sources and croplands, with the dual objectives of maximizing carbon capture and minimizing costs, present additional computational complexities. Finally, our research involves heavy-duty computing simulations to capture uncertainties associated with ERW and resulting CDR rates.
Here we will provide snippets into the technologies and methodologies we have developed to address these computational challenges. Our toolkit encompasses specialized optimization algorithms, Geographic Information Systems (GIS) to construct efficient transport networks, Life Cycle Analysis (LCA) to calculate the net Carbon Dioxide Removal (CDR), use of databases, and the utilization of machine learning techniques. We will also discuss our recent exploration of deep learning and its potential to enhance ERW modelling.
Through this presentation, we aim to illuminate the computational intricacies inherent in ERW modelling at a national scales and highlight the innovative solutions we have employed to surmount these challenges. Our research not only advances our understanding of ERW as a viable climate mitigation strategy but also contributes to the broader field of computational geoscience and climate modelling.

Speaker: Dr Euripides Kantzas (University of Sheffield)

5 Measurements in Geochemical CDR

Geochemical carbon dioxide removal (CDR) technologies capture and store carbon dioxide (CO2) from the atmosphere using alkaline materials that are rich in calcium (Ca) and magnesium (Mg). Alkaline materials include natural rocks such as basalt, industrial by-products such as steel slag, or artificially generated and industrially produced materials such as lime. Geochemical CDR technologies speed up the reactions of such materials with air or other CO2-bearing gases, and convert the CO2 into solid carbonate minerals or dissolved inorganic carbon in the ocean. Gigatonne (Gt) scale removal is potentially possible with geochemical CDR owing to the abundant quantities of alkaline materials, in addition to durable carbon storage over thousands of years.
Interest in geochemical CDR has expanded considerably over the past 5 years, as researchers and practitioners explore its feasibility. However, further research, development, and deployment of geochemical CDR may be limited by a lack of robust and standardised approaches to measurement. In this work, aspects of measurement in geochemical CDR are considered with the objectives of i) accounting for carbon accumulation in a material or solution, ii) assessing the capacity of the material to react with CO2, iii) understanding how material properties may impact the speed of reaction with CO2, iv) collecting sufficient information on a material to aid in the design of a reaction process, and v) collecting sufficient information such that risks associated with a mineral can be assessed. In order to help meet these objectives, materials properties must be collected via analytical techniques.
Here we present guidance for the application of these analytical techniques in the form of standard operating procedures (SOPs), tailored to meet the needs of geochemical CDR projects. The collection of accurate data obtained through standardised methods could facilitate project feasibility, design and operation, carbon accounting, and foster regulatory confidence in the industry. Given the often-heterogeneous nature of alkaline materials and the range of technologies that might facilitate their reaction with CO2, this document is for guidance only and the protocols should be adapted to suit the needs of the user. As the field innovates, we anticipate updating this report with additional operating procedures, and welcome such contributions to future editions.

Speaker: Dr James Campbell (Heriot-Watt University)

10:50 Coffee Break

Plenary: Session 2 - Measurements

Convener: Dr Mike Kelland

6 Opportunities and challenges for soil-based mass balance approaches to quantifying CO2 removal from enhanced rock weathering in agricultural settings

There is growing interest in the use of alkaline rock powders with high carbon dioxide removal (CDR) potential as agricultural amendments, with the goal of sequestering CO2 while providing plant-available nutrients and deacidifying soils. However, in order for this practice to be widely implemented as a negative emissions technology, there must be robust and widely accepted monitoring, reporting, and verification (MRV) of CDR rates. Site-specific and time-integrated empirical measurements of feedstock weathering rates in agricultural soils can be determined using canonical geochemical mass-balance (1,2). In this approach, elements that are assumed to be immobile during weathering are used to quantify the amount of feedstock initially present in a soil sample, and the loss of mobile cations from the solid phase is used to calculate a bulk weathering rate. Results from mesocosm experiments (2) indicate that if it can be successfully scaled, this technique could form the foundation of a model-based MRV framework to assess CDR from individual deployments.

Here, we assess the resolvability of signals for weathering of feedstocks calculated using soil-based mass balance at field scale. We present a metric for resolvability of ERW given a range of conditions for mixing, feedstock application rate, and dissolution, and test this using a spatially gridded soil database from the contiguous USA (3). We use this approach to compare the suitability of different measurable immobile trace elements and element ratios for analysis of weathering rates. Our simple framework provides a useful tool for farmers and practitioners when planning ERW feedstock deployment given site-specific conditions. We then address some challenges of implementing soil-based mass balance in field settings, using data from multi-year ERW trials (4), and discuss the role of sampling practices, laboratory analytical techniques and methods of data processing to improve confidence in results.

1 Brimhall and Dietrich (1987) https://doi.org/10.1016/0016-7037(87)90070-6
2 Reershemius, Kelland et al. (in review) https://doi.org/10.48550/arXiv.2302.05004
3 Smith et al. (2012) USGS https://doi.org/10.3133/ds801
4 Beerling et al. (in review) https://doi.org/10.48550/arXiv.2308.04302

Speaker: Tom Reershemius (Yale University)

7 Revegetation of mine waste tailings accelerates removal of atmospheric CO2

Nearly all greenhouse gas emissions pathways that restrict global temperature increase to ≤2°C above pre-industrial necessitate Carbon Dioxide Removal (CDR) from the atmosphere1. One proposed CDR solution is Enhanced Rock Weathering (ERW), which aims to artificially speed up natural silicate or carbonate weathering by applying crushed calcium and magnesium rich rocks to agricultural soils. Waste material from mining activities, such as tailings, could be used as a potential feedstock for ERW.
Here we report results of a novel ERW field experiment being conducted in collaboration with an established gold mining company in Ghana. A decommissioned tailings storage facility was re-vegetated with oil palms that were planted directly onto the surface of the mine tailings after closure of the facility in 2017. We have been working to quantify the impact that re-vegetation has had on weathering rates, and consequently on removal of atmospheric CO2. Sampling has been conducted at two sites: one where oil palms were planted on tailings, and a “control” site where oil palms have been planted on local soil.
We have quantified the carbon dioxide removed through both alkalinity generation, measured in soil pore waters, and in accumulation of organic matter in the revegetated tailings. Also, soil carbonate content, nutrient availability, and heavy metal mobilisation in the soils have been analysed using soil leaching procedures and combined with analyses of soil organic carbon to build up a full picture of weathering processes for full quantification of CDR. On-site monitoring also indicates that palms planted on tailings have higher yields of palm fruits. The approach thus holds promise as an inexpensive and efficient substitute for the practice of capping tailings ponds, that simultaneously offers the benefit of offsetting some of the CO2 produced from mining activities.

Speaker: Ms Millie Dobson (University of Southampton)

8 Yield response to Greenlandic Glacial Rock Flour applications varies as a function of initial site nutrient status

Greenlandic glacial rock flour (GRF) is a potential source of silicate minerals for CO2 uptake via enhanced weathering which would mitigate the need for energy-intensive crushing due to the naturally fine grain size (D50: 2.6 microns) of this material. The chemical makeup of this material also indicates that it may be a good source of plant nutrients, including K in particular. Results thus far have indicated that GRF can successfully improve plant growth, but the extent of its impact appears to be dependent on the initial nutrient status of the soil. Whereas in maize trials conducted on nutrient-poor soils in Ghana we have observed a 48% increase in total grain yield across 5 consecutive growing seasons after a one-time application of 50 t/ha of GRF, results in Denmark have been mixed. The same application rate of GRF increased silage maize yields by 24% and potato yields by 19% in the year of application when applied to a certified organic farm, but this increase did not persist in the following growing seasons. When applied to a conventionally managed farm with high soil K, no effect of GRF was observed on barley yields in the year of application. This year’s installation of a network of 11 new field trials will allow for improved understanding of how yield response, mineral weathering rates, and the associated uptake of CO2 vary as a function of environmental conditions and GRF application rates.

Speaker: Dr Christiana Dietzen (University of Copenhagen)

12:25 Lunch

Plenary: Session 3 - Further Enhancements

Convener: Dr Anežka Radkova

9 Enhancing Silicate Weathering of Basalt with Bacillus Subtilis: A Promising Strategy for Sustainable Agriculture

Basalt is a widely available natural silicate rock that is suitable to use in agricultural setup due to its diverse plant-relevant nutrient content. Yet, it has a rather slow weathering rate compared to minerals such as olivine and wollastonite. This is hypothesised to be partially due to formation of Fe and Al precipitates that form around the minerals, blocking bicarbonate - active site interaction in time. Therefore an agent such as a bacterium that can solubilize Fe and Al precipitates may effectively increase basalt weathering rates.
This study investigates the potential of the plant-growth promoting rhizobacterium Bacillus subtilis that was observed to have potent effect on Fe solubility to enhance basalt weathering rate in soil, thus increasing carbon sequestration. B. subtilis was reported to enhance weathering under laboratory conditions, but there is lack of data for natural conditions. We tested three cases in a soil-mesocosm experiment at room environment conditions: basalt amendment, B. subtilis amendment, and combined.
Results indicated that B. subtilis increased leachate Fe content in the absence of basalt. Extraction of soil cations displayed that B. subtilis together with basalt, compared to just basalt amendment, increased soil Fe content but not soluble Fe. It also increased soil Ca and Mg content that originate from basalt, potentially increasing the weathering rate of basalt. On the other hand, soil CO2 respiration is elevated compared to just basalt amendment, which may have implications for carbon sequestration. Further investigation is necessary to assess the implications for carbon sequestration and the practical applications of B. subtilis and basalt amendment in sustainable agriculture, particularly in plant-soil systems.

Speaker: Harun Niron (University of Antwerp)

10 Symbiotic underground allies: can mycorrhizae stimulate carbon sequestration via enhanced silicate weathering?

Arbuscular mycorrhizal fungi (AMF) are highly abundant microbes in agricultural fields. They form an obligatory symbiotic relationship with crops, providing essential nutrients such as phosphorous while receiving carbohydrates and lipids from their host plants. Moreover, AMF play a crucial role in improving soil structure, and influencing the formation and stabilization of soil organic matter. In addition, AMF also affect weathering of soil minerals either directly by e.g. serving as a sink for ions released during weathering, by increasing reactive surface area and by secreting exudates, or indirectly by e.g. increasing the total belowground carbon flux as a result of improved plant growth. Given the promising role of agricultural fields for enhanced silicate weathering (ESW), it is essential to understand the influence of AMF on the carbon dioxide removal (CDR) potential of this negative emission technology. However, this has not been studied yet.
To investigate the interaction between basalt application and AMF, a full-factorial basalt x AMF mesocosm experiment was set up. During the growing season of the crops, soil CO2 fluxes were measured, soil pore water was analyzed for weathering products, and plant growth was monitored. After the growing season, plants were harvested, soil samples were taken and carbon sequestration rates were calculated. AMF hyphal length was analyzed to investigate whether basalt application influenced AMF growth. Our preliminary results show that near the end of the growing season, dissolved inorganic carbon in the pore water increased with basalt application, which was reinforced by AMF presence. With basalt, the CO2 flux increased in presence of AMF whereas AMF did not influence the CO2 flux in the control treatment where no basalt was applied. AMF hyphal length was not affected by basalt application. Given the abundance of AMF in agriculture, and the clear influence on DIC concentrations found in this study, further investigation of its effect on the CDR potential of ESW is encouraged.

Speaker: Ms Jet Rijnders (University of Antwerp)

11 Microbial-Induced Calcite Precipitation: soil greenhouse gas fluxes using dolerite fines as source of calcium

Microbial-Induced Calcite Precipitation (MICP) is a biogeochemical process that induces the formation of carbonate minerals. Via urea hydrolysis, soil microorganisms are stimulated through supplying urea, calcium, and simple carbon nutrients. Calcium chloride (CaCl$_2$) is typically used as a source for calcium, but basic silicate rocks and other materials have been investigated as alternatives. Weathering of calcium-rich silicate rocks (e.g., basalt and dolerite) releases calcium, magnesium, and iron, process associated with sequestration of atmospheric CO$_2$ and formation of paedogenic carbonates. Soil CO$_2$ emissions associated with MICP have been reported using both sources of calcium. Because MICP involves the inorganic carbon and nitrogen cycles, other greenhouse gas fluxes, particularly N$_2$O, could potentially occur. We present an investigation of soil-atmosphere CO$_2$, N$_2$O and CH$_2$ fluxes of a MICP treated quartz-sand in a soil column set up using CaCl$_2$ or dolerite fines applied on the soil surface as sources for calcium. Low and high concentrations of urea-calcium were studied to cover soil inputs used in agricultural and engineering applications, respectively. Greenhouse gas fluxes were monitored with a PICARRO instrument over 11 days following end of MICP treatment. In addition, soil inorganic and organic carbon and their isotopic composition were determined by isotope-ratio mass spectrometry. Soil-solution was analysed for pH, total nitrogen, organic carbon, ammonium, and nitrates to monitor urea hydrolysis and nitrification processes. Results indicated urea hydrolysis, soil carbonation, CO$_2$ emissions occurred with either source of calcium, while nitrates were detected at lower concentrations than the pristine soil. Compared to treatment with CaCl$_2$, dolerite fines induced an earlier urea hydrolysis, higher consumption of organic carbon and nitrogen, higher CO$_2$ emissions, and a lower precipitation of carbonates within soil. Interestingly, N$_2$O emissions were only detected with dolerite. The results of this study highlight that weathering of dolerite fines on soil is likely to induce a faster and diverse microbial response to nutrient application, resulting in higher short term greenhouse gas emissions.

Speaker: Dr Carla Comadran Casas (James Watt School of Engineering, Advanced Research Centre, University of Glasgow)

12 ERW impacts on ecosystem services: impact on agricultural production

Speaker: Sylvia Vetter

14:55 Group Shot and Coffee

Plenary: Session 4 - Resource Estimates

Convener: Dr Mel Murphy

13 Potential for atmospheric carbon dioxide removal in mafic quarries via enhanced rock weathering of basalt fines

Enhanced rock weathering (ERW) is a recognized carbon dioxide removal (CDR) strategy that uses crushed silicate rock (e.g., basalt) to capture atmospheric CO2, offering co-benefits such as improved soil health and increased crop production [1]. One of the main disadvantages of ERW includes the production of energy needed to crush and transport rocks to their application site [2]. Basalt quarries, which are abundant throughout the United Kingdom (UK), might be capable of removing CO2 on-site by optimizing the management of their quarry fines. This approach would reduce transport-related emissions while repurposing valuable, previously underutilized material. Basalt and dolerite fines from Breedon’s Orrock Quarry and Tarmac’s Cairneyhill Quarry in Scotland are tested in this study as potential feedstocks for ERW, respectively. These samples show evidence of on-site weathering as secondary minerals are present in some areas of the fines. Thermogravimetric analysis (TGA) on these samples corroborates field observations as 1.02% and 2.22% CO2 were detected at Orrock and Cairneyhill, respectively. It is estimated that 10 kg CO2/ t Orrock fines and 25 kg CO2/ t Cairneyhill fines have been sequestered passively. Based on the CaO and MgO content, the carbonation potential is 190 kg CO2/ t Orrock fines and 160 kg CO2/ t Cairneyhill fines. Due to the challenge of accessing this potential under ambient conditions, it's essential to evaluate various on-site basalt management practices. To test this, ex-situ, column-based experiments were performed in the following manner. Fines from both sites were placed into columns with varying thicknesses (1 cm and 5 cm) and grain sizes (bulk and <75 μm). These columns were then subjected to ambient UK conditions (10 °C, 0.04% CO2) in an environmental chamber and intensified carbonation conditions (50 °C, 20% CO2) in a CO2 incubator. Both sets of experiments have been in place for three months, with monthly water addition to facilitate natural wetting and drying. Secondary minerals have formed on the bulk fines after two months, regardless of thickness or chamber conditions, with up to a 1.5 g mass increase. Orrock fines (<75 μm) in the CO2 incubator exhibit secondary precipitation, irrespective of sample thickness, displaying white patches (5 mm × 5 mm) on the surface. Upon experiment completion the columns will be sampled and analysed through TGA and total inorganic carbon to monitor CO2 sequestration extent and yield. This study has implications for the use of basalt fines for CDR at quarrying operations.

[1] Beerling, D.J. et al., 2020. Potential for large-scale CO2 removal via enhanced rock weathering with croplands. Nature, 583(7815): 242-+. [2] Edwards, D.P. et al., 2017. Climate change mitigation: potential benefits and pitfalls of enhanced rock weathering in tropical agriculture. Biology Letters, 13(4).

Speaker: Ms Amanda Stubbs (University of Glasgow)

ERW2023 presentation - Amanda Stubbs.pptx

14 An inventory of UK mineral resources suitable for Enhanced Rock Weathering

Enhanced Rock Weathering (ERW), a technology based on amending soils with crushed calcium- and magnesium-rich silicate minerals has substantial large-scale CO2 removal potential globally and in the UK. Evaluation of the available resources of these minerals and current production capacity is crucial for early-stage deployment of this approach. A robust understanding of the potential limitations in exploiting these resources is also required to ensure the scalability of ERW. This paper provides a spatial inventory of the basic silicate rock resources in the UK along with the current production capacity and permitted reserve of quarries extracting these rocks. We also integrate spatial data to assess the potential environmental and social impacts of current rock extraction. Outcrops of basic silicate rocks in the UK cover an area of approximately 10,180 km2 which are mainly distributed in Northern Ireland and in the central belt of Scotland. 68 active and 100 inactive quarries were identified within outcrops of basic silicate rocks. 14.8 Mt yr-1 of basic silicate rock are estimated to be extracted from the 68 active quarries from which up to 3.7 Mt yr-1 of basic silicate waste fines is estimated to be produced which may be available for ERW in the UK. Transport distances are calculated between basic rock resources and the UK’s croplands where these materials may be applied for ERW. The relative appropriateness of the UK’s croplands for CDR are also calculated based on their proximity to basic rock resources and climate parameters that control the rate of EW on croplands.

Speaker: Dr Mohammad Madankan (Research Associate)

15 Enhanced rock weathering opportunities in Spain

As an EU Member State, Spain is required to adopt national soil, energy and environmental plans to make notable progress on its climate actions and land use management policies. A recent study [1] highlighted the high potential for Spain to host viable geochemical CO2 removal (CDR) schemes to make valuable contributions towards national reduction targets, EU environmental regulations and global climate goals. Spain hosts a notionally high CDR capacity thanks to extensive mafic-ultramafic rocks, high industrial by-product tonnages, and appropriate land uses to host projects. Enhanced rock weathering (ERW) was highlighted as one potential CDR strategy that could be pursued within Spain. This study aims to expand on these initial findings to better constrain ERW feedstocks, host settings and synergistic approaches within Spain.
Due to suitable bedrock geology and viable feedstock providers within the regions, there are possibilities for ERW schemes to be hosted within Galicia, Andalucía, Castilla-La Mancha and the Canary Islands. Of these regions, Galicia (northwest Spain) has been pinpointed for more detailed investigations based on the high reactivity of rocks that are exploited across the region (e.g., dunite, peridotite, serpentinite and amphibolite). The temperate and rainy climate of Galicia is beneficial for crop production, and would also encourage ERW if implemented. Extensive agricultural coverage, targeted restoration areas, mined and quarried land and extensive coastline exposure could provide suitable ERW site opportunities across Galicia.
One potential barrier for widescale ERW implementation in Galicia is the general prevalent soil conditions across the region. Soil pH in Galicia are typically ultra-acidic (<3.5) to acidic (5.2), containing high concentrations of chromium and nickel. Soils with a pH <5.2 may be considered unsuitable candidates for ERW approaches, as dissolution of minerals by non-carbonic acids would not produce alkalinity, thus reducing CDR efficiency. As a complementary approach to ERW and means of mitigation, specifically-designed technosols, soils created by human intervention, could be utilised to improve soil health, enhance soil carbon storage and act as a long-term carbon sink. Technosols have been used on degraded soils in Galicia for remediation purposes, restoring health and value to soils in industrial areas. It is considered that mixed technosol-ERW feedstock approaches could act to alter soil pH, nutrient availability, physical properties, microbial communities and plant growth to increase soil organic and inorganic contents.
ERW opportunities of Spain, specifically Galicia, have been assessed through geochemical modelling, benchtop experiments, fieldwork and GIS-based approaches. The occurrence and availability of mafic-ultramafic rocks and industrial wastes in areas proximal to degraded soils and agricultural lands provide opportunities to explore joint technosol-ERW feedstock approaches, with the intention of achieving multiple benefits – notably, enhanced CDR (with potential upscale in Spain, across the EU and beyond) and improved soil health.
This work forms part of the DETAILS project (Developing enhanced weathering methods in mine tailings for CO2 sequestration; Marie Skłodowska-Curie grant agreement ID: 101018312).
References: [1] Bullock et al., 2023. Geochemical carbon dioxide removal potential of Spain. Sci. Total Environ., 867, 161287.

Speaker: Dr Liam Bullock (Geosciences Barcelona-CSIC)

16 Challenges to deployment of ERW at scale: lessons from Brazil and the UK

Speaker: Prof. David Manning (Newcastle University)

17:00 Drinks Reception - Networking

18:00 Coach to Royal Botanic Garden

Whisky Tasting: Whisky Tasting Experience

19:45 Call for Dinner

Conference Dinner

King and Queen coronation visit to Edinburgh:
https://www.gov.scot/publications/king-and-queen-visit-to-edinburgh-july-2023-events/

Edinburgh open top bus tours:
https://edinburghtour.com/

Go up Arthur's seat.

Whisky experience:
https://www.scotchwhiskyexperience.co.uk/

22:00 Guests Departure