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Representative sandstone samples from Mesohellenic Trough (NW Greece) were selected to investigate the geochemical reactions that occur when they come in contact with CO 2 under representative in-situ conditions (T = 70 °C, P = 150 bar, 6 months reaction in batch experiments). Those sandstones consisted of predominant calcite and quartz, with lesser amounts of feldspars, chlorite, ankerite, dolomite, kaolinite, montmorillonite and muscovite. After reaction with CO 2 , the brine became acidic and was enriched in cations as a result of mineral dissolution. Minor mineralogical changes were observed that involved: a) the dissolution of carbonate minerals and b) the incongruent dissolution of chlorite to form clays and silica. The results related to these, have been linked with geochemical modelling using the PHREEQC code. Simulation results for a 10 ka time period predicted that chlorite was expected to dissolve completely within 100 years, leading to boehmite growth and increasing the mass of dolomite. Feldspars were expected to react at a later stage in the reaction sequence. Sensitivity tests were run to access the effect of various adjustable parameters on the outcome results. The geochemical experiments and modelling lend support to the view that Pentalofos and Tsotyli sandstone formations of the Mesohellenic Trough are suitable for the long-term storage of CO 2 produced in the neighbouring lignite-fired power plants, at least in terms of mineralogy and geochemistry. [ABSTRACT FROM AUTHOR]

Storage of CO 2 into geological formations, such as deep saline aquifers and depleted oil/gas reservoirs, is being investigated to help reduce releases to the atmosphere. A critical issue is the long-term efficacy of engineered (man-made) hydrated cement seals that surround or plug boreholes. In order to investigate the impact of CO 2 interactions with hydrated cement, the present study focuses on the alteration processes that were observed in a hydrated cement core (based on Type-G Portland cement) after laboratory experimental reaction with a CO 2 -saturated brine for 6 months. The carbonated cement block consisted of an orange outer zone, an alteration rim, and the intact cement core. The PHREEQC geochemical code was used to simulate the experimental conditions and data using 1D reactive transport modeling. The first phases to dissolve were portlandite, CS and ettringite providing calcium to solution. Three CaCO 3 polymorphs were predicted to precipitate, but the less stable of these (aragonite, vaterite) were transformed to calcite over time. According to simulations the final product after 1000 years of reaction will be 68% calcite, 18% Friedel's salt and 14% Al-Fe-Si hydro/oxides. As the reaction front moved within the sample, porosity decreased due to the formation of amorphous phases and carbonates. The proposed model is a useful tool in describing longer-term hydrated cement alteration behavior during CO 2 geological storage and to compare their results with in situ observations from field experiments. [ABSTRACT FROM AUTHOR]

Underground coal gasification (UCG) is the in-situ conversion of deep underground coal to synthesis gas for heating, chemical manufacturing and power generation. UCG has been the subject of extensive pilot testing but technical and environmental concerns remain, not least its greenhouse gas emissions. An attractive solution is to combine UCG with CO 2 capture and storage (CCS) so that the CO 2 generated from the UCG and combustion of synthesis gas is re-injected back underground in the UCG cavities, adjacent unmineable coal seams and stressed strata. Thereby the emissions from UCG are eliminated and deep coal reserves become a new source of energy supply. This paper reviews the recent global development of UCG projects, the research progress of UCG technology and the technical developments and economic feasibility of UCG-CCS in recent EU projects. [ABSTRACT FROM AUTHOR]

CO 2 storage potential in Greece concerns mainly aquifers and a few hydrocarbon fields. The potential for CO 2 storage in oil and gas fields in Greece lies offshore, in the Prinos-Kavala basin, in NE Greece, whereas the biggest share of the point source CO 2 emissions come from NW Greece. Potential for storage also exists in lignite fields, which have been extensively mined for power generation. This paper presents an overview of the potential for CO 2 storage throughout various sites in Greece, including the Mesohellenic Trough (MT), located in Northwestern Greece. Geological model building of the MT allowed to make an assessment of the CO 2 storage potential of the trough and provided an estimation of the CO 2 storage capacity in the Pentalofos and Eptahori reservoirs. According to the geological model, characterized by horizontal maximum dimensions of 47 km by 100 km and covering a surface area of 3813 km 2 , the deepest point where we can store CO 2 corresponds to the base of the Tsarnos member, at -2544 m depth. We estimate that altogether we can store up to a maximum of 728 Gt of CO 2 in the Pentalofos Formation (Tsarnos and Kalloni Members) and Eptahori Formation. The location of the potential storage sites, relatively close to emission points, forms interesting combinations, which are briefly presented in this paper. The results presented here will serve as a basis for pursuing this worthwhile piece of research in order to determine the most reliable and most cost efficient ways of transporting and storing CO 2 in Greece. [ABSTRACT FROM AUTHOR]

Highlights: [•] Consistency, stability and confidence are three indicators of opinion quality. [•] We compare opinion quality after focus groups and information-choice questionnaires. [•] Information-choice questionnaires result in higher-quality opinions than focus groups. [Copyright &y& Elsevier]

Abstract: The energy balance of Greece is strongly dependent on imported oil. The rather late introduction of natural gas has increased the diversity of the energy mix while the share of renewable sources in primary energy supply still needs to increase according to the existing potential. Yet, Greece as one of the most of the EU developed countries encounters a serious task: the need to increase its electricity production of almost 5% per year but at the same time to reduce the CO2 emissions according with the National and International (20-20-20) regulations and allocation plans. Therefore reducing CO2 emissions has become a major priority for national government. In addition, from 2013, there will be the full implementation of the wholesale market in the European Trading Scheme (ETS) which is currently in the last stages of a transition phase.In Greece electricity is mainly generated from lignite, thus making the electricity sector one of the main contributors to GHG emissions with a level above 40% of the total country and higher than the corresponding average of the rest of the EU countries. The possible implementation of Carbon Capture and Storage (CCS) technologies would then become very decisive due to the large use of the lignite as fuel in the country electricity mix. CCS technology has the potential of increasing the flexibility on the achievement greenhouse gas emissions reduction by allowing to continue to use fossil fuels, which still guarantees feasibility in the energy sector. This work presents a roadmap with the modeling of the main technologies associated to the CCS and its implementation into the Greek energy system considering existing National and International Strategic energy plans under different scenarios. The implementation of CCS technologies would have a large influence on the national electrical power production, having the responsibility for large shares of the emissions reduction that can potentially achieved in this sector. For this purpose, TIMES (The Integrated MARKAL/EFOM System) has been chosen as the principal tool for building a techno-economic model of the Greek energy system and its possible evaluation over time (2040). [Copyright &y& Elsevier]

Abstract: The mobility of inorganic pollutants is of key concern for a range of industrial and engineering applications of fly ash produced during the combustion of lignite in power generation. This paper investigates the role that the geochemical features of lignite, the ash composition and the partitioning of elements during combustion play in determining leaching properties of lignite fired by-products. The work is based on surveys on three lignite-fired power plants in Greece. Calcium-rich ashes show a high abatement potential for SO2 and other gaseous pollutants. For most elements, the concentrations in the parent lignite and the ashes follow the same trend. Relative enrichments in Cd, Co, Cr, Cu, Mo, Ni, Pb, U, V, W, Zn fingerprint the regional and local geological settings of the lignite basins. The total and leachable concentrations of highly volatile elements are strongly influenced by the interaction with ubiquitous free lime. A broad array of elements is highly insoluble in alkaline ash, while a few oxyanionic-forming elements display substantial mobility. Their mode of occurrence in the parent lignite plays a primary role in the leaching of combustion ashes. The outcomes of this study may assist in addressing the impact of co-firing high ash or high Ca alternative fuels on the leaching properties of combustion by-products. [Copyright &y& Elsevier]

Abstract: The representative survey studies provide a comprehensive database on the public awareness and perception of CCS in six selected European countries. Our results provide insights into the public understanding and knowledge of energy related issues and CCS topics. The embedded experimental research provides insights into how information affects CCS perceptions. The results discuss implications for CCS communication methods. [Copyright &y& Elsevier]

Abstract: Previous research has shown that public knowledge and awareness of carbon dioxide capture and storage (CCS) is very limited. As a result, traditional surveys designed to collect public opinions about CCS do in fact assess so-called pseudo opinions. Pseudo-opinions are of very low quality because they are mostly unstable and inconsistent. Therefore, they are not predictive for actual and future public support for or opposition against CCS. As compared to pseudo opinions, opinions expressed after the public has been provided with factual information about CCS are likely to be of higher quality. Focus group discussions and Information-Choice Questionnaires (ICQs) are two research techniques frequently used in the CCS literature that aim to collect such informed public opinions. In this study, we examined which of these two research technique leads to the highest quality opinions (i.e., to opinions that are consistent, stable, and that people are confident about). Our results showed that ICQs yielded higher-quality opinions than focus group discussions. Practical implications and recommendations are discussed. [Copyright &y& Elsevier]

Abstract: Polish bituminous (PB) and South African (SA) coal fly ash (FA) samples, derived from pilot-scale circulated fluidized bed (CFB) combustion facilities, were utilized as raw materials for the synthesis of zeolitic products. The two FAs underwent a hydrothermal activation with 1M NaOH solution. Two different FA/NaOH solution/ratios (50, 100g/L) were applied for each sample and several zeolitic materials were formed. The experimental products were characterized by means of X-ray diffraction (XRD) and energy dispersive X-ray coupled–scanning electron microscope (EDX/SEM), while X-ray fluorescence (XRF) was applied for the determination of their chemical composition. The zeolitic products were also evaluated in terms of their cation exchange capacity (CEC), specific surface area (SSA), specific gravity (SG), particle size distribution (PSD), pH and the range of their micro- and macroporosity. Afterwards the hybrid materials were tested for their ability of adsorbing Cr, Pb, Ni, Cu, Cd and Zn from contaminated liquids. Main parameters for the precipitation of the heavy metals, as it was concluded from the experimental results, are the mineralogical composition of the initial fly ashes, as well as the type and the amount of the produced zeolite and specifically the mechanism by which the metals ions are hold on the substrate. [Copyright &y& Elsevier]

Abstract: The work aims at providing an initial estimation of CO2 transportation cost by means of pipelines. CO2 will be stored in geological formations in North Greece where the majority of the thermal power plants located. Particularly, it was examined the CO2 storage in saline aquifers and oil reservoir. The scenarios were developed taking into consideration factors such as the potential storage period, CO2 storage capacity of the geological media, the emissions. The transportation cost of CO2 was estimated using the methodology proposed by the IEAGHG. The results show that the transportation cost varies from 0.39 $/tn CO2 up to 0.45 $/tn CO2 (0.08 $/tn/100Km to 0.26 $/ton/100 Km). Additionally, the CO2 emissions that come from the fossil fueled power plants can be stored in the oil reservoir and saline aquifer of Prinos for 51 years while in saline aquifers of W. Thessaloniki and Pentalofos for 60 and 54 years respectively. Taking into account the abovementioned results, the recommended approach seems to be a quite attractive solution. [Copyright &y& Elsevier]

Abstract: The chemical and mineralogical composition of fly ash samples collected from different parts of a laboratory and a pilot scale CFB facility has been investigated. The fabric filter and the second cyclone of the two facilities were chosen as sampling points. The fuels used were Greek lignite (from the Florina basin), Polish coal and wood chips. Characterization of the fly ash samples was conducted by means of X-ray fluorescence (XRF), inductive coupled plasma-optical emission spectrometry (ICP-OES), thermogravimetric analysis (TGA), particle size distribution (PSD) and X-ray diffraction (XRD). According to the chemical analyses the produced fly ashes are rich in CaO. Moreover, SiO2 is the dominant oxide in fly ash with Al2O3 and Fe2O3 found in considerable quantities. Results obtained by XRD showed that the major mineral phase of fly ash is quartz, while other mineral phases that are occurred are maghemite, hematite, periclase, rutile, gehlenite and anhydrite. The ICP-OES analysis showed rather low levels of trace elements, especially for As and Cr, in many of the ashes included in this study compared to coal ash from fluidised bed combustion in general. [Copyright &y& Elsevier]

Abstract: In this paper the mineralogy and geochemistry of Greek and Chinese coal fly ash are examined. Annual production of fly ash in China is around 160Mt while in Greece lignite fly ash accounts around 10Mt. Even though the mineralogical and chemical composition of the fly ashes coming from these two countries differs, there are common questions on the utilization of this material. The variation of the Greek fly ash’ chemical composition, from Ca-poor to Ca-rich fly ash, has resulted to applications such as dam construction, use in cement and possibly in concrete and road construction. The Chinese fly ash, which is rich in mullite, is broadly applied for brick making. [Copyright &y& Elsevier]

A probabilistic geotechnical design optimization framework for large open pit excavations is proposed in the present work. An appropriate objective function is formulated in terms of normalized cost of excavation, while the overall slope angle constitutes the decision variable. Probability of slope's failure is computed via Monte Carlo simulations. Optimization curves identifying the optimum slope's angle are developed for different risk and volume factors. For illustrative purposes, a typical example of a surface lignite mine is analyzed and results are thoroughly discussed. The suggested methodology can be used as a complementary tool in the decision analysis process of similar projects. [ABSTRACT FROM AUTHOR]

Fly ash from two lignite-fed power stations in Greece (Megalopolis and Meliti) has been utilized to synthesize zeolitic materials with upgraded adsorption capacity. Two different siliceous fly ash samples were subjected to hydrothermal treatment at fixed solid/liquid ratio and constant temperature. The zeolitic products have been characterized for their microstructure, chemical, and mineralogical composition by means of SEM, AAS, and XRD, respectively. The primary zeolitic crystals identified were phillipsite and thomsonite, in Megalopolis and Meliti fly ash, respectively. In light of their prospective utilization as liquid-phase sorbents, the specific surface area and porosity of materials were also determined, by means of N 2 -porosimetry. The zeolitic samples were tested for their actual heavy metal-removal capacity by water sampled from active lignite mines in Northern Greece. Artificial aquatic samples with known concentration of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were also tested, showing that the synthetic zeolitic materials are good to uptake a wide variety of potential pollutants with up to 100% efficiency. The efficiency of the synthetic zeolitic materials was comparatively assessed, showing that the more intense the presence of phillipsite in the synthetic materials, the greater the uptake rates for certain groups of trace elements. [ABSTRACT FROM AUTHOR]

Abstract Carbonation of industrial wastes rich in earth-alkali oxides is found to have a significant potential for CO 2 sequestration. This process opens new perspectives not only for carbon dioxide mitigation, but also for the valorization and new applications of industrial waste materials from coal-burning power plants. In this study, mineral carbonation of high–calcium fly ash is investigated under dry and moist conditions in a continuous flow reactor during up to 2 h, at temperatures ranging from 160 to 290 °C and CO 2 pressures between 1 and 6 bar. A comprehensive characterization of treated and untreated samples was carried out before and after carbonation using X-ray diffraction, X-ray fluorescence spectroscopy, thermogravimetric analysis, infrared spectroscopy and scanning electron microscopy. The maximum sequestration capacity achieved was 117.7 g CO 2 /kg fly ash (48.14% carbonation efficiency) under dry conditions. Results showed that increasing the pressure and temperature enhances the process of carbonation, as well as the presence of moderate amounts of water vapor in the CO 2 gas flow. Newly formed carbonates were always present in the treated samples. This study shows that about 21% of all CO 2 emissions of a coal-burning power plant could potentially be sequestered as carbonates. Highlights • This work presents carbonation of high-calcium fly ashes in dry and moist conditions. • Results show that carbonation occurred both with and without water vapor presence. • Higher carbonation efficiency is achieved with temperature and pressure increase. • SEM analysis showed the fly ash cenospheres evolution with growing calcite. • Maximum carbonation efficiency achieved is 48.14%. [ABSTRACT FROM AUTHOR]

Phosphorus (P) recovery from wastewater is of great interest especially when the loaded adsorbent can be used in the agriculture as slow-release fertilizer. The application depends on environmental concerns related to the chemical modification of the adsorbent and the release of toxic compounds from the loaded material to the soil or the water during adsorption. The present work focused on the phosphate (PO 4 -P) removal from aqueous solutions under low P concentrations (0.5–10 mg/L) by using Ca(OH) 2 -pretreated natural zeolite (CaT-Z). As activation agent, Ca(OH) 2 presents benefits in terms of pretreatment costs and environmental impact of the applied adsorbent. The pretreatment of natural zeolite (clinoptilolite) with 0.25 mol/L Ca(OH) 2 led to an increase of P removal from 1.7 to 97.6% at initial P concentration of 10 mg/L, pH 7 and 298 K. Low residual concentrations of 81–238 μg P/L were achieved at 298 K rendering CaT-Z a promising sorbent for tertiary wastewater treatment. At 200 mg P/L, the adsorption capacity was 7.57 mg P/g CaT-Z. The P removal efficiency was pH-independent suggesting a beneficial use of CaT-Z under acidic and alkaline conditions. Adsorption was found to be an endothermic and slow process reaching equilibrium after 120 h, whereas the half of the PO 4 -P was adsorbed in the first 8 h. The applied kinetic models showed that both film and intraparticle diffusion contributed to phosphate removal. Phosphate sorption decreased in the presence of the anionic surfactant SDS, Fe 2+ , HCO 3 − , acetate and citrate anion. The predominant mechanisms of ligand exchange and Ca-P surface precipitation were confirmed by the IR-ATR and SEM-EDS analyses, respectively. [ABSTRACT FROM AUTHOR]