• Energy Research

The life-cycle environmental impacts of geothermal power generation are highly variable and depend on many site-specific conditions. The objective of this work is the identification of the most influential parameters for estimating the environmental impacts of geothermal electricity production. First, we developed a general model for computing the impacts of both conventional and enhanced geothermal technologies. The model is validated against selected literature studies for the climate change category. We then use Global Sensitivity Analysis (GSA) to evaluate the contribution of each parameter to the overall variance of the model's output. The results of the GSA suggest that i) the uncertainty of environmental impact estimates can be significantly reduced by obtaining more accurate values for a small number of key parameters, such as the installed capacity of the plant, operational emissions of CO2 and the depth and capacity of wells; and ii) the majority of parameters do not affect significantly the environmental impact estimates and therefore can be fixed anywhere within their range of variability. Finally, we discuss some of the limitations of the present study and propose approaches that could be implemented to overcome such limitations.

The transparent, flexible, and open-source Python library carculator_truck is introduced to perform the life cycle assessment of a series of medium- and heavy-duty trucks across different powertrain types, size classes, fuel pathways, and years in a European context. Unsurprisingly, greenhouse gas emissions per ton-km reduce as size and load factor increase. By 2040, battery and fuel cell electric trucks appear to be promising options to reduce greenhouse gas emissions per ton-km on long distance segments, even where the required range autonomy is high. This requires that various conditions are met, such as improvements at the energy storage level and a drastic reduction of the greenhouse gas intensity of the electricity used for battery charging and hydrogen production. Meanwhile, these options may be considered for urban and regional applications, where they have a competitive advantage thanks to their superior engine efficiency. Finally, these alternative options will have to compete against more mature combustion-based technologies which, despite lower drivetrain efficiencies, are expected to reduce their exhaust emissions via engine improvements, hybridization of their powertrain, as well as the use of biomass-based and synthetic fuels.

Abstract This paper outlines the approach to the evaluation of sustainability of current and future electricity supply options of interest for a major Swiss utility Axpo Holding AG. The motivation behind this effort has been to provide a solid basis for a state-of-the-art interdisciplinary assessment and use this framework within a dialog with a wide spectrum of stakeholders. The development and implementation of the methodology was coordinated by Axpo in co-operation with the Paul Scherrer Institut (PSI) and other scientific institutions. The evaluation covers environmental, social and economic dimensions of sustainability. Methods used include among others life cycle assessment (LCA), impact pathway approach (IPA) and probabilistic safety assessment (PSA). The associated databases developed by PSI have been extensively used, subject to major extensions necessary for analyzing the future technologies. Learning curves were employed for future cost estimates. Furthermore, particularly in the social area expert surveys were used. The results were aggregated using total (internal plus external) costs approach and multi-criteria decision analysis (MCDA). For MCDA a set of criteria and the associated indicators was established. In total 75 indicators were quantified, including 11 environmental, 33 social and 31 economic. Eighteen current and 18 future technologies have been analysed including nuclear as well as fossil and renewable technologies. Total costs were estimated for these technologies providing a clear ranking with nuclear having the lowest costs and some of the renewables showing remarkable cost reductions until 2030. This ranking is partially controversial mainly due to the limited representation of social aspects in the total costs. The results of MCDA-applications involving elicitation of preferences from a relatively homogeneous stakeholder group, i.e. 85 employees of the Axpo Group (including also NOK, EGL, CKW and Axpo IT), are summarized. In addition, sensitivity of technology ranking to preference profiles is demonstrated. Broader consideration of social factors favours renewables and depending on the specifics of preference profiles may lower the ranking of nuclear. Further applications of the MCDA-approach with various stakeholder groups are planned.

This work quantifies current and future costs as well as environmental burdens of large-scale hydrogen production systems on geographical islands, which exhibit high renewable energy potentials and could act as hydrogen export hubs.

Abstract Large-scale greenhouse gas (GHG) emission reductions are crucial for achieving the European goals for climate change mitigation. A frequently discussed option is carbon capture and storage (CCS), where CO 2 emissions from point sources are captured and stored in geologic structures. However, concerns about risks of leakages of CO 2 from geological storage have been raised. These risks could be avoided with ex situ mineral carbonation, where the captured CO 2 is stored in an inert and stable solid form after reacting with calcium and magnesium silicates. For a comprehensive assessment of the environmental and economic performance of this CO 2 storage option in fossil-fueled power generation chains, life cycle assessment (LCA) and levelized cost of electricity (LCoE) calculations are performed. The implementation of CCS using mineral carbonation leads to life cycle GHG emission reductions of 15–64% and LCoE increases of 90–370% on a per kWh el basis compared to a reference power plant without CCS. The life cycle GHG emission reduction achievable with mineral sequestration is less substantial than with geological storage of CO 2 due to significant energy and chemical additives requirements. Accordingly, LCA results for other environmental indicators are worse than those of the reference plant without CCS and the geological CO 2 storage option.

Life cycle inventories (LCI) of electricity generation and supply are among the main determining factors regarding life cycle assessment (LCA) results. Therefore, consistency and representativeness of these data are crucial. The electricity sector has been updated and substantially extended for ecoinvent version 3 (v3). This article provides an overview of the electricity production datasets and insights into key aspects of these v3 inventories, highlights changes and describes new features. Methods involved extraction of data and analysis from several publically accessible databases and statistics, as well as from the LCA literature. Depending on the power generation technology, either plant-specific or region-specific average data have been used for creating the new power generation inventories representing specific geographies. Whenever possible, the parent–child relationship was used between global and local activities. All datasets include a specific technology level in order to support marginal mixes used in the consequential version of ecoinvent. The use of parameters, variables and mathematical relations enhances transparency. The article focuses on documentation of LCI data on the unlinked unit process level and presents direct emission data of the electricity-generating activities. Datasets for electricity production in 71 geographic regions (geographies) covering 50 countries are available in ecoinvent v3. The number of geographies exceeds the number of countries due to partitioning of power generation in the USA and Canada into several regions. All important technologies representing fossil, renewable and nuclear power are modelled for all geographies. The new inventory data show significant geography-specific variations: thermal power plant efficiencies, direct air pollutant emissions as well as annual yields of photovoltaic and wind power plants will have significant impacts on cumulative inventories. In general, the power plants operating in the 18 newly implemented countries (compared to ecoinvent v2) are on a lower technology level with lower efficiencies and higher emissions. The importance of local datasets is once more highlighted. Inventories for average technology-specific electricity production in all globally important economies are now available with geography-specific technology datasets. This improved coverage of power generation representing 83 % of global electricity production in 2008 will increase the quality of and reduce uncertainties in LCA studies worldwide and contribute to a more accurate estimation of environmental burdens from global production chains. Future work on LCI of electricity production should focus on updates of the fuel chain and infrastructure datasets, on including new technologies as well as on refining of the local data.

Abstract For light-duty vehicles (LDVs), alternative powertrains and liquid fuels based on renewable electricity are competing options considered by policymakers and stakeholders for achieving necessary CO2 emission reductions in the transport sector. While the urgency of climate change and the need to reach mitigation targets are well understood, system-wide implications along other sustainability dimensions need further exploration. We integrate a detailed transport system model into an integrated assessment framework and couple it with prospective life cycle impact analysis. This allows to assess different technological pathways of the European LDV fleet until 2050 for a comprehensive set of environmental and resource depletion indicators. Results indicate that greenhouse gas emissions drop significantly in all mitigation scenarios. However, impacts increase in several non-climate change impact categories even with fully renewable electricity supply. Additional impacts arise from the production of battery and fuel-cell components, and from a significant rise in electricity demand, most prominently for synthetic fuels. We consequently find that changes in mobility life-styles and in the relevant industrial processes are paramount to reduce environmental impacts from a climate-friendly LDV fleet across all categories.

This review provides a perspective on how to conduct future Life Cycle Assessment (LCA) studies of carbon dioxide removal technologies in a consistent way avoiding common mistakes, which should be addressed to aid informed decision making.