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While geological models traditionally focus on the natural status of the underground, the shallow subsurface has been significantly altered by human activities over centuries. Particularly in urban contexts, ground has been raised, reworked, filled-in or disturbed in other ways. The rationale behind these alterations is as varied as the characteristics of the associated anthropogenic deposits: large-scale structures such as residential and industrial areas built on extensive sheets of filling materials or reclaimed lands are intertwined with smaller-scale features related, for example, to road and railway infrastructures, dikes or landfills. Their composition is equally diverse, ranging from displaced natural materials, such as crushed rocks, gravel, sand or clay, to artificial substances like recycled steel slags, concrete or rubble, or mixtures of these. Gaining knowledge on the presence and characteristics of such deposits is highly relevant, as their physical and chemical behaviour may differ significantly from those of natural deposits. The significance of anthropogenic deposits is increasingly recognized in urban geology. Resolving the geometry and properties of the urban shallow subsurface is essential for anticipating associated risks, for example dealing with pollution, ground stability or distorted water infiltration patterns. Anthropogenic deposits are, however, often scantily archived in permit documentation or represented on (geological) maps. Within the GSEU (Geological Service for Europe) project, the GSB is contributing to the task to develop a common, international vocabulary to describe all aspects of anthropogenic deposits, allowing standardised representation and characterisation in geological models. In parallel, VITO is developing shallow subsurface urban models for the Flemish government (VPO) within the VLAKO-framework, such as the published model of the Antwerp harbour and city. As the anthropogene inherently is part of these models, we are always aiming to better incorporate these deposits into the models. However, modelling the anthropogene presents unique challenges due to its high-resolution variability, scarcity of input data, and dynamic nature. It requires an approach that differs radically from traditional geological modelling techniques, in which depositional concepts related to the sedimentational or structural environment can be incorporated. In this presentation we will outline how we integrate various 1D, 2D and 3D sources to identify and characterize anthropogenic deposits and incorporate these insights in a 3D geological model of the anthropogene. This methodology is applied to the urban periphery of Brussels, where a new 3D geological model is being developed to support infrastructure projects and urban planning with special focus on the ring road (R0) of Brussels. Secondly, we will evaluate current lithological standards, vocabulary and stratigraphic approaches to characterize anthropogenic deposits. We will discuss their applicability in Flanders with practical examples from the periphery of Brussels. Ultimately, improving the representation of the anthropogene in geological models will significantly enhance their utility for urban planning, environmental management, and the sustainable utilization of the subsurface in urban areas.

Nearly every geological subdiscipline relies to some degree on regional geological knowledge. In the introductory section of most geological papers it is standard practice to provide regional geological background information. Stratigraphic terminology is often well defined while other disciplinary concepts rely, at least to some degree, on generally agreed definitions or hierarchical schemes, such as paleontological, structural or magmatic terminology. This, however, is much less the case for the regional geological building blocks. Their names are usually composed of a combination of a geographical locality and a geological term. A few examples from Belgium are Brabant Massif, Campine Basin, Stavelot-Venn Inlier, and Malmedy Graben. Most of these have in common that, although their importance is well recognised, their definitions are vague and sometimes even conflicting, in that their meaning may differ between contexts and authors. Even if their meaning has drifted or become less exact, as a result of their frequent historical use, they commonly remain in use today. This issue is not exclusive to Belgium, but seems to be an altogether historic and worldwide phenomenon. Recently within Europe there is a growing awareness of this issue, resulting in important but rather isolated efforts to better structure and define regional information (Hintersberger et al. 2017; Németh 2021; Le Bayon et al. 2022) which have been brought together through pan-European cooperation (GSEU – Horizon Europe 101075609). The central element that seems to encompass most geologic features, is the lithotectonic unit (a distinct unit based on its partly separate geological history; URI: http://inspire.ec.europa.eu/codelist/GeologicUnitTypeValue/lithotectonicUnit). Grabens, basins and inliers are examples of lithotectonic units. In order to define and describe these units more accurately, lithotectonic limits are introduced. These are planar features, such as faults and unconformities, that correspond to the geologic events that formed the lithotectonic unit (Piessens et al. 2024). All information is organised and linked in vocabularies (thesauri) that together not only adequately define each concept, but also determine the relations between them, placing them in space and geological time (Plašienka 1999). This outlines the core methodology, around which 2D and 3D multi-scale visualisations are built, annotations can be added, existing ontologies can be linked (such as the ICS Geological Time Scale Ontology; Cox and Richard, 2005) and newly developed extensions such as the Modified Wilson Cycle (Németh 2021). As such, the work at Belgian level is closely linked to the ongoing international developments. Making use of the ongoing developments at European level, Belgium was the first country to set up a lithotectonic working group that became operational in 2023. Its first goal is to provide a lithotectonic framework that describes a starting set of main geological units and limits in Belgium, according to emerging European standards (the work at European level is linked to the implementation of INSPIRE and 195 is in communication with the GeoSciML community), by the end of 2024. The working group meets approximately every 2 months, and organisationally resides under the National Commission for Stratigraphy in Belgium. The working group will soon be looking for additional experts (junior and senior) in its continuing effort to identify and define broad superstructures, detail the regional geology to the more local level, to tackle new types of lithotectonic elements, or better address parts of geological history. Potential candidates are encouraged to contact one of the authors or the NCS secretariat. Cox SJD, Richard SM (2005) A formal model for the geologic time scale and global stratotype section and point, compatible with geospatial information transfer standards. Geosphere 1:119. https://doi.org/10.1130/GES00022.1 Hintersberger E, Iglseder C, Schuster R, Huet B (2017) The new database “Tectonic Boundaries” at the Geological Survey of Austria. Jahrbuch der geologischen Bundesanstalt 157:195–207 Le Bayon B, Padel M, Baudin T, et al (2022) The geological-event reference system, a step towards geological data harmonization. BSGF - Earth Sci Bull 193:18. https://doi.org/10.1051/bsgf/2022017 Németh Z (2021) Lithotectonic units of the Western Carpathians: Suggestion of simple methodology for lithotectonic units defining, applicable for orogenic belts world-wide. Mineralia Slovaca 2:81–90 Piessens K, Walstra J, Willems A, Barros R (2024) Old concepts in a new semantic perspective: introducing a geotemporal approach to conceptual definitions in geology. Life Sciences Plašienka D (1999) Definition and correlation of tectonic units with a special reference to some Central Western Carpathian examples. Mineralia Slovaca 31:3–16

1. Les monuments funéraires trévires 1.1. Introduction Les monuments funéraires des Trévires sont le sujet de deux projets de recherche, menés par l’Académie des Sciences Autrichienne en coopération avec l’Université de Luxembourg d’une part et l’Université de Francfort et le Rheinisches Landesmuseum Trier d’autre part (Mahler, 2017). L’objectif de cette contribution est de présenter quelques réflexions préliminaires sur les analyses pétrographiques effectuées dans le cadre du projet austro-luxembourgeois. La cité des Trévires, située en Gaule Belgique, est appréciée depuis longtemps pour la quantité et la richesse de ses monuments funéraires de l’époque gallo-romaine, dont ceux provenant de Neumagen (von Massow, 1932) et d’Arlon (Espérandieu, 1913 ; Colling et al., 2009), pour ne citer que les ensembles les plus célèbres. Toutefois, cet ensemble n'a jamais fait l'objet d'un traitement scientifique et d'une évaluation exhaustive, étant donné que la zone d'étude est située à la frontière linguistique franco-allemande et comprend quatre États modernes (Kremer, 2018a ; Kremer, 2018b). De plus, les nouvelles découvertes des dernières décennies, comme celle du mausolée de Bertrange (Krier, 2003 ; Kremer, 2009) ou des monuments du Titelberg (Kremer, 2019), apportent des éclairages nouveaux sur l'évolution de la situation dans cette région et invitent à une enquête approfondie de l’ensemble des monuments connus. Dans le cadre du projet austro-luxembourgeois sur la partie occidentale de la civitas Treverorum, des analyses pétrographiques ont été initiées d’abord afin d'assurer une caractérisation et une détermination de provenance correctes des matériaux pierreux utilisés, ensuite afin d'obtenir des données nouvelles sur des questions d'organisation d'ateliers, de chronologie ou de relations économiques. Nous espérons contribuer à une meilleure compréhension de l'utilisation de la pierre dans le Nord de la Gaule, où la région trévire constituait une tache blanche sur la carte (Boulanger & Moulis, 2018). Une sélection représentative a été faite parmi les monuments accessibles de la zone de recherche ; toutefois, en l’absence d’exhaustivité, les résultats concernant la fréquence d'apparition des matériaux n’ont pas de valeur statistique. Ont été analysés les blocs de monuments funéraires exposés dans les musées de Luxembourg (MNHA), Arlon, Virton, Buzenol et Trèves. Des prélèvements ont été réalisés sur une série d’échantillons mise à disposition par le Centre national de recherche archéologique (CNRA) du Grand-Duché de Luxembourg. - Joint project FWF/FNR I 2269-G25: « Funerary Monuments from Western civitas Treverorum in an Interregional Context. The Inter-Connected Evaluation of a Socio-Historically Relevant Category of Finds ». Direction de projet : Gabrielle Kremer, ÖAI/ÖAW (lead) et Andrea Binsfeld, UniLu. Nous remercions les membres de l’équipe Sophie Insulander, Jean Krier, Sebastian Mühling et Christine Ruppert ainsi que les collègues du CNRA et du MNHA Luxembourg, du IAL et des Musées d’Arlon, Virton et Trèves. - Projet financé par la DFG : « Römische Grabdenkmäler aus Augusta Treverorum im überregionalen Vergleich: mediale Strategien sozialer Repräsentation ». Direction de projet : Anja Klöckner et Markus Scholz, Univ. Francfort, et Marcus Reuter, RLM Trier.

Introduction L’étude du mobilier en pierre fait désormais partie des analyses incontournables après toute opération de fouille. Elle apporte des informations sur l’approvisionnement en matières premières, sur leur usage et sur les modalités de leur mise en forme. Abordée de manière diachronique, elle permet de déceler les variations des pratiques techniques et économiques au cours du temps. L’étude des meules est devenue emblématique de cette discipline géo-archéologique puisqu’elle met en évidence des dynamiques économiques qui ont des répercussions sur le cadre social des populations. Au cours du temps, des roches spécifiques ont été sélectionnées pour répondre à des besoins précis, en lien avec l’un des secteurs les plus primordiaux qui soient : celui de l’alimentation. Un véritable système de recherche de la ressource, d’exploitation, de production, de transport et de commercialisation s’est établi pour approvisionner des populations plus ou moins proches des lieux de production et désireuses d’acquérir et d’utiliser des marchandises efficaces et parfois esthétiques. Au début du 5e siècle av. J.-C. dans le nord-est de la péninsule ibérique, les techniques de mouture bénéficient d’un progrès qui s’étend progressivement à toute l’Europe de l’ouest, à savoir le passage du mouvement alternatif (moulin va-et-vient) au mouvement rotatif. Le moulin rotatif arrive en Gaule du nord à partir de la seconde moitié du 3e siècle av. J.-C. (La Tène moyenne), mais le moulin reste encore domestique. Le saut technologique que l’on observe durant l’époque gauloise est donc plus qualitatif que quantitatif : les conditions de la préparation alimentaire s’améliorent nettement, dans un cadre socio-économique qui varie peu, celui du foyer familial. Ce n’est que dans la première moitié du 1er siècle de notre ère, avec le regroupement des populations dans les villes, les camps militaires et les grands établissements ruraux, que s’installent de grands moulins à eau ou à traction animale dont les meules commencent à être produites par les ateliers régionaux. Ces derniers s’étaient déjà adaptés au passage du moulin va-et-vient au moulin rotatif : malgré une courte période d’une à deux générations pendant laquelle ont été préférées des roches tendres , les matériaux durs exploités au moins depuis le Néolithique pour la confection de meules va-et-vient sont repris en main dès la fin de La Tène moyenne pour produire des meules rotatives. En Germanie inférieure et dans le Nord de la Gaule, la plupart des carrières de meules rotatives identifiées ont ainsi livré des ébauches de meules va-et-vient antérieures à la fin de l’époque gauloise : respectivement dans les coulées volcaniques de l’Eifel (HÖRTER, 1994 ; MANGARTZ, 2008), dans le secteur d’Hirson/Macquenoise (Aisne/Hainaut - PICAVET et al., 2018) et à Lustin (Namur) dont les gisements nous intéressent ici. Si toutes ces carrières ont produit des meules rotatives à La Tène finale (La Tène moyenne est mal appréhendée en Belgique), puis à l’époque romaine, les carrières elles-mêmes et leurs ratés de fabrication sont encore méconnus. Un travail de prospection de longue haleine en milieu forestier a pour objectif de les caractériser. Les carrières de Lustin, situées dans le Bois des Acremonts et dans le Bois de Nîmes (prov. Namur, Belgique), ont été parcourues par Dominique Daoust (fig. 1). Il a identifié plusieurs dizaines d’ébauches de meules rotatives manuelles dont les dimensions évoquent une datation gauloise et/ou romaine précoce (autour d’une quarantaine de centimètres, parfois moins). Le travail d’analyse de ces ébauches, toujours en cours, permet aujourd’hui de préciser les modalités de l’exploitation du conglomérat rouge dit « Poudingue de Burnot » autour de la moyenne vallée de la Meuse à ces périodes anciennes. Les productions de ces carrières sont essentiellement connues par leur diffusion sur les sites de consommation en Belgique et dans le Nord de la France. Leur reconnaissance est assurée par les descriptions pétrographiques des géologues Gilles Fronteau et Éric Goemaere, qui pointent la Formation de Burnot (unité lithostratigraphique autrefois appelée « Poudingue de Burnot » et d’âge burnotien, étage aujourd’hui tombé en désuétude : DEJONGHE et al., 2006) et nous autorisent à identifier les niveaux géologiques d’origine du matériau. Notons que la Formation de Rivière qui la surmonte directement peut apparaître dans les mêmes carrières et a pu fournir des meules ponctuellement. À la faveur d’une archéologie préventive dynamique et à l’issue de deux thèses de doctorat (RENIERE, 2018 ; PICAVET, 2019), l’enregistrement de nombreux produits finis géolocalisés dessine les contours de leur aire de répartition en Gaule du nord, tout en fournissant des appuis chronologiques solides. Recensées entre La Tène finale et le Haut-Empire romain, parfois jusqu’au début du 3e siècle, les meules en Poudingue de Burnot occupent ainsi une région située entre celle approvisionnée par les carrières dites de Macquenoise à l’ouest (Hirson/Macquenoise : PICAVET et al., 2018) et celle qui reçoit les productions l’Eifel à l’est (Mayen, Rhénanie-Palatinat : MANGARTZ, 2008), alors que les grès quartzitiques tertiaires sont majoritaires au nord et au nord-ouest chez les Ménapiens au Haut-Empire (RENIERE et al., 2016). Faisant le lien entre les carrières et les produits de consommation rejetés après usage, une cargaison de produits semi-finis draguée dans la Meuse au début du 20e siècle évoque enfin leur transport aval vers la ville romaine de Namur où l’on peut envisager la présence d’ateliers de finition et de redistribution (cf infra).

One of the greatest challenges of the last decades in the fight against climate change has been to achieve net-zero emissions by mid-century. According to the US EPA (2016), in 2014, global anthropogenic emissions of carbon dioxide (CO2) accounted for ~64% of the greenhouse effect. Carbon dioxide capture and storage (CCS) plays an irreplaceable part as a mitigation technology that avoids CO2 emissions at their source and bridges the transition into a non-carbon-based energy future. The International Energy Agency (IEA) estimates that the need to store CO2 will grow from 40 Mt/y at present to more than 5000 Mt/y by 2050. Additionally, in the IEA’s Sustainable Development Scenario, which aims for global net-zero CO2 emissions from the energy sector by 2070, CCS needs to become a global industry supporting emissions reductions across the overall energy system. CCS technologies essentially consist of capturing and compressing the CO2 at the source and then transport it towards deep suitable rock formations where it is injected to be permanently stored. The key to successful and permanent CO2 storage is the proper analysis and characterization of the reservoir and seal formation. Among the types of reservoir suitable for CO2 storage are unmined coal beds, depleted oil and gas fields, EOR/EGR, saline aquifers, man-made caverns, and basaltic formations (IPCC, 2005). The storage capacity of any of these reservoirs is the subsurface commodity whose quantities and properties are assessed when existing data is provided. Capacity estimations bring their own level of uncertainty and complexity according to the scale at which they are addressed and the nature of the geological conditions of the reservoir. This degree of uncertainty should be accounted for in every estimation (Bradshaw et al., 2007) Resource classification systems (RCS) are frameworks that establish the principles and boundaries for each level of capacity assessment. By making use of these frameworks, it is possible to properly allocate the stage of development of a resource (United Nations, 2020). For every level of assessment, the principles of the estimation change and so do the scale and purpose. As the analysis moves forward, a prospective site develops and exhaustive information is acquired, initial estimations are adjusted, and uncertainty is likely to reduce. Additionally, different economic, technical, regulatory, environmental and societal factors are integrated into the assessment to bring the estimations under present conditions. For instance, if the storage capacity is to be matched with a CO2 source, detailed simulations and analyses regarding injectivity, supply rate, potential routes and economic distances must be performed to achieve a realistic estimation. However, an assessment where the main goal is to merely quantify the space available to store CO2 in a reservoir, does not consider the aforementioned limitations and will carry higher risk and uncertainty in its estimation (Bradshaw et al., 2007). Even though resource classification systems provide a solid foundation for CCS projects, they do not provide the input parameters and analyses needed to reach every level of assessment. This is why storage capacity estimation methodologies go hand in hand with RCS given that the former can give information related to the parameters and constraints considered in the estimation. No standard process has been proposed that can be followed from the starting level of a CO2 storage capacity assessment until a fully developed carbon storage resource; that is, a CO2 storage site ready to become fully operational. This paper aims to develop a methodology where the fundamental steps needed to go through every level of the resource classification systems are standardized. This methodology intends to serve as a general baseline that, regardless of the geological settings and techno-socio-economic conditions, can be adopted for any CCS assessment. The proposed methodology is built by reviewing the available capacity estimation methods for every level of assessment and identifying social, technical and economic aspects that come into play as the resource is being developed. Considering that capacity estimation methodologies can vary their approach even for the same level of assessment, the rationales behind them are expected to be determined. Such rationales can be related to in-place policy restrictions, geographical economic behavior, or the nature of the parameters contemplated. Additionally, PSS, an in-house developed tool that can assess CO2 storage reservoirs at different levels, will be proposed within the methodology. This tool is a bottom-up geotechnical and economic forecasting simulator that can generate source-sink matching for CCS projects, where technical, economic, and geological uncertainties are handled through a Monte Carlo approach for limited foresight (Welkenhuysen et al., 2016). Acknowledgements This research is carried out under the LEILAC2 project, which receives funding from the European Union’s Horizon 2020 research and innovation program under grant agreement number 884170. The LEILAC2 consortium consists of: Calix Europe SARL, HeidelbergCement AG, Ingenieurbüro Kühlerbau Neustad GmbH (IKN), Centre for Research and Technology Hellas (CERTH), Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Politecnico di Milano (POLIMI), Geological Survey of Belgium (RBINS-GSB), ENGIE Laborelec, Port of Rotterdam, Calix Limited, CIMPOR-Indústria de Cimentos SA and Lhoist Recherche et Development SA. References Bradshaw, J., Bachu, S., Bonijoly, D., Burruss, R., Holloway, S., Christensen, N. P., & Mathiassen, O. M. (2007). CO2 storage capacity estimation: Issues and development of standards. International Journal of Greenhouse Gas Control, 1(1), 62–68. https://doi.org/10.1016/S1750-5836(07)00027-8 IPCC. (2005). Carbon Dioxide Capture and Storage. https://www.ipcc.ch/report/carbon-dioxide-capture-and-storage/ United Nations. (2020). United Nations Framework Classification for Resources: Update 2019. UN. https://doi.org/10.18356/44105e2b-en US EPA. (2016). Global Greenhouse Gas Emissions Data. US EPA. https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-data Welkenhuysen, K., Brüstle, A.-K., Bottig, M., Ramírez, A., Swennen, R., & Piessens, K. (2016). A techno-economic approach for capacity assessment and ranking of potential options for geological storage of CO2 in Austria. Geologica Belgica. http://dx.doi.org/10.20341/gb.2016.012

Knowledge on the environmental impacts of geothermal energy is of major importance to understand the role this technology could play in the transition towards sustainable energy systems. Life cycle analysis (LCA) methodology is a widely used tool for assessing the environmental impacts of products and systems, which has been implemented numerous times on geothermal systems. Previous reviews on geothermal LCA studies identify large variability on the reported environmental impacts. In this work we aim to provide a more in-depth analysis to explain the variability across the different LCAs. We review 28 LCA studies on geothermal energy published between 2005 and 2020, following a four step reviewing sequence; in step 1 we identify the LCA methodological choices and the plant geo-technical characteristics, in step 2 we identify the LCA results and the LCI inputs, in step 3 we perform contribution analysis based on the reported results and in step 4 we investigate the sensitivity and scenario analysis performed in the studies. If the data is available we triangularly evaluate the reported impacts considering a) the plants’ geo-technical characteristics, b) the hotspot analyses results and c) the Life cycle inventory (LCI) inputs. We focus our analysis on the six most frequently assessed impact indicators (GWP, AP, HTP, FETP, CED, ADP)* and distinguish between the different energy conversion technologies used for geothermal energy exploitation. This way we aim to provide a more transparent picture on the variability of environmental impacts across the LCAs by focusing on the environmental hotspots and on the cause-effect relationships between geo-technical parameters and the environmental impacts. We also aim for drawing LCA guidelines for future LCA studies on geothermal systems and proposing methods for impact mitigation. The variability on the LCA results is caused by differences on the choices of the LCA practitioners, on the energy conversion technologies used, on geological parameters and on plant design parameters. Most studies focus on the GWP and AP impacts, while information for the rest of the impacts is much more limited. For flash and dry steam power plants the direct emissions of non-condensable gases (NCGs) emerging can cause high GWP, AP, FETP and HTP impacts depending on the geofluid’s composition. The CED and ADP impacts are dominated by the steel and diesel consumption during the development of the wells. Thus differences on the geo-technical parameters determining the power output and the total material and energy consumption cause the variability on the reported results. Direct emissions of NCGs do not emerge in plants utilizing binary technology. In these plants the development of the wells dominates the impacts and this phenomenon is more intense when EGS-binary plants are investigated due to the large depth drilled. Also the production of the working fluid used in the ORC and its annual leakage can highly affect the GWP impact in these plants depending on the type of working fluid used. In heating plants high amounts of grid-electricity are needed for the plant operation as no power is produced. Therefore differences in the fossil-fuel-intensity of the electricity mix supplying the plant can result in large variability. The choice of the LCA practitioner to include or not the heat distribution network in the boundaries of the system also affects the results, while a significant portion of the impacts is caused during the development of the wells. Combined heat and power plants using flash or binary technology present similar results. However the co-production of heat and power is expected to lead to some benefits. A direct correlation between the GHGs and the NH3/H2S direct emissions with the GWP and AC impacts, respectively, is observed for flash and dry steam power plants. Direct emissions are determined by the geofluid composition which highly varies between different reservoirs. For mitigating these impacts the installation of abatement systems shall be considered, while the identification of the geofluid composition and of the natural emissions emerging prior to the plant development is suggested for estimating the actual anthropogenic emissions. For plants utilizing binary technology and heating plants it is observed that higher capacity generally leads to lower GWP and AP impacts per functional unit. The capacity is a product function of the temperature and production flow. Similar observation can be extracted for the temperature while this is not the case for the flow. No clear correlation can be seen between the impacts and the depth. This is because larger depths lead –on the one hand– to higher impacts because of higher material and energy consumption which are compensated –on the other hand– to the increase on the fluid temperature and flow. For mitigating impacts caused during the construction phase the use of renewable energy sources for supplying the machinery used is suggested, while proper fluid re-injection should be designed for keeping the capacity constant during the operation. Also for binary plants the working fluid shall be selected such that its GWP impact is low, while for heating plants the installation of a small ORC unit shall be considered if the conditions are appropriate for meeting the pumping needs of the plant. The reviewed studies show that geothermal energy exploitation can lead to significant environmental benefits compared to fossil sources, as most of the times the impacts caused by geothermal plants are in the range of other renewable sources. Further research is needed on deep geothermal energy exploitation to better understand its environmental impacts. A significant portion of the impacts is caused during the operation of the plants regardless of the technology used (direct emissions, electricity consumption, working fluid losses, make-up well drilling). All of the LCA studies reviewed are static LCAs. Thus a dynamic LCA framework considering the time aspect is needed for better estimations of the environmental impacts. Also consequential LCAs on geothermal energy plants need to be conducted in order to assess how the global environmental impacts may change by the wider implementation of geothermal energy. In addition, future LCA studies shall also focus on environmental impacts other than the GWP as information regarding them is limited. Finally the sustainability of geothermal investments is to be further explored by investigating the social impacts of geothermal development and comparing them to other energy sources but also the financial aspect of such investments. Acknowledgments This research is carried out under the DESIGNATE project, which receives funding from the BELSPO BRAIN-be 2.0 research program under contract nr B2/191/P1/DESIGNATE. * GWP: Global Warming Potential, AP: Acidification Potential, HTP: Human Toxicity Potential, FETP: Freshwater EcoToxicity Potential, CED: Cumulative Energy Demand, ADP: Abiotic resources Depletion Potential

The development of geothermal energy is below the European National Renewable Energy Action Plans' anticipated trajectory. For deep geothermal energy projects in particular, multiple sources of uncertainty in combination with high upfront investment costs result in a major investment risk, hampering the mobilization of required capital (Compernolle et al., 2019). The uncertainty sources include market uncertainty, uncertainty regarding new technologies and uncertainty inherent to working with subsurface data. The objectives of the DESIGNATE project for deep geothermal systems in Belgium, including applications in abandoned mines are two folds. First, to create tools for integrated forecasts under uncertainty and second to set-up a methodological framework for territorial Life Cycle Analysis (LCA) considering surface and subsurface impacts. To do so, analytical reservoir models will be developed to assess the effect of uncertainties about geological data and concepts on the performance and impact of the geothermal applications. These will be coupled with a techno-economic analysis in combination with a territorial, environmental life cycle analysis. To evaluate the impact of different policy measures, the techno-economic analysis consists of a Monte Carlo simulation model that integrates both market and geological uncertainties and a project developers' option to wait or abandon the geothermal project development at different steps in the development of the project (Welkenhuysen et al., this conference). As a preliminary step, the influence of the rollout time of a heat network on the risk and on the profitability is investigated. At the start often only a part of the district heating network is in place at the time of commissioning and the geothermal plant operates at much lower capacity. Part of the capacity is foreseen for district heating networks linked to residential districts expected to be built or renovated in the near future. In this research, the change in income of a project considering a stepwise rollout of a district heating network compared to a full load from the start, in combination with a reduced maximum capacity of the geothermal plant compared to the expected output is calculated. This is done with a simplified spreadsheet techno-economic model, limiting variability to the rollout scenarios. For the calculation, data provided by the project developer HITA of the Turnhout NW geothermal project is used. In the next section the four cases used to evaluate the risk and profitability linked to the changes in the rollout time of a heat network are described. In the first case, the base case, the production plant is assumed to work at full capacity once the construction of the geothermal plant is achieved. Full capacity means that the production plant will be working at 100% during the heating season. Additional production for cooling or for heat storage in summertime are not taken into account. The second case considers that the maximum production capacity is 20% lower than in the first case due to lower-than-expected reservoir temperature or flow rate. In the third case, the full capacity is equal to the one of the base case but will be reached in three steps, simulating a growing demand by adding new district heating networks. The demand is expressed as a percentage of the expected maximum production capacity of the geothermal plant. At the start of production, the geothermal plant runs at 50%. After 5 years this is increased to 75% and after 10 years full capacity is reached. The fourth and last case is similar to the third case, with a stepwise increase of the demand, but the maximum production capacity is, as in second case, 20% lower. Because the demand is lower than the total capacity in the first 10 years, the production plant will however be able to supply the required energy. Only after 10 years when the demand rises to the expected maximum production capacity, only 80% of the required energy can be delivered without additional investments. As such, the income of the project will be the same the first 10 years compared to the third case. In a best-case scenario, demand and rollout of a district heating network will be fast and the production plant will run at full capacity during the heating season from the start (case 1). This is however unlikely and assuming this to be the base case will result in many projects not reaching predetermined targets, as the income of the project will be lower during the first years of production. In this respect, the third case or a similar scenario is a better option to use as a base case. This will put more stringent conditions on the expected output parameters of the production well to ensure an economic viable project, and hence provide a more realistic outlook. When using case 3 as the base case this also has the complementary benefit of reducing the risk related to the maximum production capacity. If the real maximum production capacity is lower than expected, the reduction of income will be lower than the decrease in the maximum production capacity. In other words, a reduction of 20% of the maximum production capacity will not lead to a reduction of 20% of the income, but will be between 0 and 20%, depending on the interest rate and on the time frame to reach full capacity. Acknowledgments This research is carried out under the DESIGNATE project, which receives funding from the BELSPO BRAIN-be 2.0 research programme under contract nr B2/191/P1/DESIGNATE. HITA kindly provided input for the development for this case study. References Compernolle, T., Welkenhuysen, K., Petitclerc, E., Maes, D. & Piessens, K., 2019. The impact of policy measures on geothermal energy investments. Energy Economics, 84, 104524. https://doi.org/10.1016/j.eneco.2019.104524 Welkenhuysen, K., Compernolle, T., Kaufmann, O., Laenen, B., Meyvis, B., Piessens, K., Gousis, S., Dupont, N., Harcouet-Menou, V. & Pogacnik, J., this conference. Decision support under uncertainty for geothermal applications: case selection and concept development.

In order to meet climate goals and provide energy security, geothermal energy can play an important part in Belgium’s energy production portfolio. The current implementation of geothermal energy in Belgium is very limited, making accurate forecasts about the economic potential difficult. In the DESIGNATE project, tools and workflows are developed to investigate the potential of deep geothermal energy and geothermal applications in abandoned mines in Belgium, considering uncertainties at reservoir, technology and economic level. The goal of this project is to make forecasts about the role of these geothermal applications in the Belgian energy portfolio and provide support for strategic planning of subsurface activities by: explicitly considering uncertainties in modelling non-standard geothermal resources; creating tools for integrated forecasts under uncertainty; setting up a methodological framework for territorial LCAs considering surface and subsurface impacts; and analysing interferences and their consequences for geothermal energy deployment in Belgium. These workflows will be developed for and applied to five real and theoretical case studies throughout Belgium, in different geological settings. A first case is the Balmatt deep geothermal project, a deep geothermal research project led by VITO in Mol, of which two wells are operational as a doublet. To allow for a realistic economic assessment, this case takes the basic structure and development of the Balmatt project, but as if it would be a commercial doublet project at the same location and in the same Carboniferous strata. A second case is a deep doublet system in NW Turnhout, currently under development by the geothermal development company HITA. This project allows supplying heat to part of the city of Turnhout’s residential and tertiary sector’s buildings. A third case involves the application of a novel single-well technology for geothermal heat extraction To compensate for the unknowns of the new technology, a more uniform and predictable reservoir type was chosen for this application: the Cretaceous deposits in the Campine Basin. The fourth case will investigate a new deep geothermal doublet in the Mons Basin, the Deep Mons project. At Porte de Nimy, close to a hospital, two wells of about 2.5km depth are planned to reach the Carboniferous. A fifth and last case is the application of an open geothermal system in former coal mine galleries. Preliminary, the Péronnes-lez-Binche coal mines were selected, as the structural separation of the galleries in a shallower colder part and a deeper warmer part allows for several applications such as seasonal use of heat and cold. Because a portfolio of methods will be developed to analyse different aspects of these projects, a solid common base is needed across all methods. These “project concepts” start from a decision tree, listing the major decision steps for each case, such as seismic exploration, well drilling, and the potential use cases. Additionally, options for waiting and abandoning the project are also included. Other data such as duration and cost are tied to this framework. Figure 1 shows a flow chart of such a decision tree for the Balmatt case. Because of their flexibility and speed, analytical solutions will be developed from numerical models for simulating the reservoir behavior and predict the evolution of temperature and pressure. The project uses an innovative approach by stepping away from simple well designs and homogeneous reservoirs, and introducing uncertainty. These analytical models will provide direct input for a geological techno-economic assessment (G-TEA), a territorial life cycle assessment (LCA), and a new version of the PSS simulator. Project development is simulated considering the analytical reservoir models as resource, the technical and economic aspects of project development, heat transport, energy demand, environmental impact, energy market and the policy framework. Acknowledgements This research is carried out under the DESIGNATE project, which receives funding from the BELSPO BRAIN-be 2.0 research programme under contract nr B2/191/P1/DESIGNATE.

In order to reach greenhouse gas emission reduction targets, atmospheric CO2 emissions from all industrial sectors need to be avoided. Globally, the cement production industry emits 2.4 Gt CO2 per year, or 7% of all CO2 emissions (IEA). While about a third of this could be reduced by using renewable energy sources, the remainder are process emissions from the calcination process. Lime or CaO is produced by heating limestone (CaCO3), emitting CO2. The Australian company Calix has developed a direct separation technology for capturing these process emissions; a pilot-scale installation is operational at the Lixhe cement plant in Belgium (Figure 1). The EU H2020-funded LEILAC2 project (Low Emission Intensity Lime and Cement 2: Demonstration Scale) upscaling and integrating a novel type of carbon capture technology. This technology aims to capture, at low cost, unavoidable process emissions from cement and lime plant. This large-scale capture plant will be installed at the Heidelberg Cement’s plant in Hannover, Germany, capturing 20% of a typical cement plant’s CO2 emission. Apart from the physical installation and operation of the capture unit, a business case will be developed for the downstream components of transport, use and geological storage for the captured CO2. In order to develop a business case, a very large number of options, combinations and scenarios for each these components need to be evaluated, taking into account the intricacies of for example dealing with geological data in economic calculations. The PSS suite of geo-techno-economic simulators has been developed by the Geological Survey of Belgium, specifically for creating forecasts on the deployment of CO2 capture and geological storage (CCS) technologies (Welkenhuysen et al., 2013). In PSS, investment decisions for the full CCS chain are simulated as a forecast in a non-deterministic way, considering uncertainty and flexibility. Especially for matching storage, these elements are essential. While capture in this demonstration project is a given, several scenarios will be analyzed: the current demo-scale, full-scale capture, and CO2-network integration. Due to its location, several CO2 transport options can be considered at the Hannover plant: from low-volume truck, railway or barge transport, up to ships and pipelines. Special attention is given to possible connections with ongoing and planned initiatives for infrastructure and hub development such as the Porthos project in the port of Rotterdam or the Northern Lights project offshore Norway. In the wider area around the capture location, North-Western Europe including the North Sea offshore area, there are many potential storage options available. Offshore storage options will be the primary targets for assessment, with many (nearly) depleted hydrocarbon fields and saline aquifers that are present in the southern North Sea. Storage aspects are treated as stochastic parameters, with for example storage capacity and injectivity of the reservoirs represented by probability density functions. In order to compare storage options, the degree of knowledge, uncertainty and economic and practical development feasibility of such a storage location needs to be assessed. An analysis of such storage classification systems is created by Tovar et al. (this conference). With the above-mentioned PSS method and CCS project development options, source-sink matching is performed to create forecasts on project and network development. Results will provide insight in the probability of preferred storage option development for steering exploration and development efforts, preferred transport modes and routes, the optimal timing of investments, and the influence of market parameters, such as the ETS price of CO2 emissions. Acknowledgments This research is carried out under the LEILAC2 project, which receives funding by the European Union’s Horizon 2020 research and innovation program under grant agreement number 884170. The LEILAC2 consortium consists of: Calix Europe SARL, HeidelbergCement AG, Ingenieurbüro Kühlerbau Neustad GmbH (IKN), Centre for Research and Technology Hellas (CERTH), Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Politecnico di Milano (POLIMI), Geological Survey of Belgium (RBINS-GSB), ENGIE Laborelec, Port of Rotterdam, Calix Limited, CIMPOR-Indústria de Cimentos SA and Lhoist Recherche et Development SA. References IEA, 2020. Energy Technology Perspectives 2020. https://www.iea.org/reports/energy-technology-perspectives-2020 Tovar, A., Piessens, K. & Welkenhuysen, K., this conference. Ranking CO2 storage capacities and identifying their technical, economic and regulatory constraints: A review of methods and screening criteria. Welkenhuysen K., Ramírez A., Swennen R. & Piessens K., 2013. Strategy for ranking potential CO2 storage reservoirs: A case study for Belgium. International Journal of Greenhouse Gas Control, 17, 431-449. http://dx.doi.org/10.1016/j.ijggc.2013.05.025