Search results

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

Phosphorus fertilisation (eutrophication) is expanding oxygen depletion in coastal systems worldwide. Under low-oxygen bottom water conditions, phosphorus release from the sediment is elevated, which further stimulates primary production. It is commonly assumed that reoxygenation could break this “vicious cycle” by increasing the sedimentary phosphorus retention. Recently, a deepwater inflow into the Baltic Sea created a natural in situ experiment that allowed us to investigate if temporary reoxygenation stimulates sedimentary retention of dissolved inorganic phosphorus (DIP). Surprisingly, during this 3-year study, we observed a transient but considerable increase, rather than a decrease, in the sediment efflux of DIP and other dissolved biogenic compounds. This suggested that the oxygenated inflow elevated the organic matter degradation in the sediment, likely due to an increase in organic matter supply to the deeper basins, potentially combined with a transient stimulation of the mineralisation efficiency. As a result, the net sedimentary DIP release per m2 was 56 %–112% higher over the years following the re-oxygenation than before. In contrast to previous assumptions, our results show that inflows of oxygenated water to anoxic bottom waters can increase the sedimentary phosphorus release.

Background: Lake Tanganyika is the world’s second deepest lake. Its diverse cichlid assemblage offers a unique opportunity for studying a deep-water host-parasite model in freshwater. Low host specificity and a broad host range including representatives of the Bathybatini tribe in the only monogenean parasite described from this habitat, Cichlidogyrus casuarinus Pariselle, Muterezi Bukinga & Vanhove, 2015 suggest a link between lower specificity and lower host density. Conversely, high host specificity and species richness are reported for monogeneans of the lake’s littoral cichlids. We further investigated whether the deep-water environment in Lake Tanganyika is really monogenean species-depauperate by investigating the monogenean fauna of Trematocara unimaculatum (a representative of the tribe Trematocarini, the sister lineage of the Bathybatini) and Benthochromis horii, a member of the tribe Benthochromini, found in the same deep-water habitat as the already known hosts of C. casuarinus. Methods: Sclerotised structures of the collected monogenean individuals were characterised morphologically using light microscopy and morphometrics. Results: Both examined cichlid species are infected by a single monogenean species each, which are new to science. They are described as Cichlidogyrus brunnensis n. sp., infecting T. unimaculatum, and Cichlidogyrus attenboroughi n. sp., parasitising on B. horii. Diagnostic characteristics include the distal bifurcation of the accessory piece in C. brunnensis n. sp. and the combination of long auricles and no heel in C. attenboroughi n. sp. In addition C. brunnensis n. sp. does not resemble C. casuarinus, the only species of Cichlidogyrus thus far reported from the Bathybatini. Also Cichlidogyrus attenboroughi n. sp. does not resemble any of the monogenean species documented from the pelagic zone of the lake and is among the few described species of Cichlidogyrus without heel. Conclusions: As two new and non-resembling Cichlidogyrus species are described from T. unimaculatum and B. horii, colonisation of the deep-water habitat by more than one morphotype of Cichlidogyrus is evident. Based on morphological comparisons with previously described monogenean species, parasite transfers with the littoral zone are possible. Therefore, parasites of pelagic cichlids in the lake do not seem to only mirror host phylogeny and the evolutionary history of this host-parasite system merits further attention.

Windmills monitoring: outreach 2005-2015

Wind monitoring Activity report 2013-2014.

To date, only one mitogenome from an Antarctic amphipod has been published. Here, novel complete mitochondrial genomes (mitogenomes) of two morphospecies are assembled, namely, Charcotia amundseni and Eusirus giganteus. For the latter species, we have assembled two mitogenomes from different genetic clades of this species. The lengths of Eusirus and Charcotia mitogenomes range from 15,534 to 15,619 base pairs and their mitogenomes are composed of 13 protein coding genes, 22 transfer RNAs, 2 ribosomal RNAs, and 1 putative control region CR. Some tRNAs display aberrant structures suggesting that minimalization is also ongoing in amphipod mitogenomes. The novel mitogenomes of the two Antarctic species have features distinguishing them from other amphipod mitogenomes such as a lower AT-richness in the whole mitogenomes and a negative GC- skew in both strands of protein coding genes. The genetically most variable mitochondrial regions of amphipods are nad6 and atp8, while cox1 shows low nucleotide diversity among closely and more distantly related species. In comparison to the pancrustacean mitochondrial ground pattern, E. giganteus shows a translocation of the nad1 gene, while cytb and nad6 genes are translocated in C. amundseni. Phylogenetic analysis based on mitogenomes illustrates that Eusirus and Charcotia cluster together with other species belonging to the same amphipod superfamilies. In the absence of reference nuclear genomes, mitogenomes can be useful to develop markers for studying population genetics or evolutionary relationships at higher taxonomic levels.