• Energy Research
• Closed Access close

Abstract Rare earth permanent magnets are important components for modern (energy) technologies and are employed to reduce GHG emissions and combat climate change. The process of extracting these minerals from the ore has contentious economic, environmental and social implications. While the environmental impacts of their production have already been analyzed in several studies, the economic and the social perspective is still under-researched. The Social Life Cycle Assessment (S-LCA) approach employed in the present research explores whether there is a difference in social risks for rare earth permanent magnet production from three different rare earth ore production locations and the associated value chains. While one is located completely in China, another is composed of processes in Australia and Malaysia. The third process chain combines processes in the United States and Japan. The Product Social Impact Life Cycle Assessment (PSILCA) 2.0 database is used to assess the social implications. The analysis focuses on value chain actors, a stakeholder group of great interest to businesses but often underrepresented in S-LCA research. The impact categories describing this stakeholder group pertain to issues of social responsibility along the value chain, fair competition and corruption. Overall, the US value chain indicates the lowest level of social risk along the supply chain. However, in order to gain a deeper understanding of the social risks a sectoral and geographical analysis is conducted. Across all three cases, the mineral, fossil fuel and chemical sectors are shown to be problematic.

Abstract Microgrids integrating local renewable energy sources at low-voltage level show promising potentials in realizing a reliable, efficient, and clean supply of electricity. Further improvements are expected when such a microgrid is operated based on direct current (dc) instead of alternating current (ac) infrastructure for power distribution commonly in use today. Our study aims to systemically quantify the gap between environmental impacts of microgrids at building level using the case study of power distribution within office buildings. For this purpose, a scalable comparative life cycle assessment (LCA) is conducted based on a technical bottom-up analysis of differences between ac and dc microgrids. Particularly, our approach combines the micro-level assessment of required power electronic components with the macro-level requirements for daily operation derived from a generic grid model. The results indicate that the environmental impacts of employed power electronics are substantially reduced by operating a microgrid based on dc power distribution infrastructure. Our sensitivity analyses show that efficient dc microgrids particularly lead to savings in climate change impact emissions. In addition, our study shows that the state-of-the-art scaling rules of power electronics currently used in LCAs leads to inaccurate results. In contrast, the proposed methodology applies a more technical approach, which enables a detailed analysis of the environmental impacts of power electronic components at system level. Thus, it provides the foundation for an evaluation criterion for a comprehensive assessment of technological changes within the framework of energy policy objectives.

Abstract The controversial and highly emotional discussion about biofuels in recent years has shown that greenhouse gas2 (GHG) emissions can only be evaluated in an acceptable way by carrying out a full life cycle assessment (LCA) taking the overall life cycle including all necessary pre-chains into consideration. Against this background, the goal of this paper is it to analyse the overall life cycle of a hydrogen production and provision. A state of the art hydrogen refuelling station in Hamburg/Germany opened in February 2012 is therefore taken into consideration. Here at least 50% hydrogen from renewable sources of energy is produced on-site by water electrolysis based on surplus electricity from wind (mainly offshore wind parks) and water. The remaining other 50% of hydrogen to be sold by this station mainly to hydrogen-fuelled buses is provided by trucks from a large-scale production plant where hydrogen is produced from methane or glycerol as a by-product of the biodiesel production. These two pathways are compared within the following explanations with hydrogen production from biomass and from coal. The results show that – with the goal of reducing GHG emissions on a life cycle perspective – hydrogen production based on a water electrolysis fed by electricity from the German electricity mix should be avoided. Steam methane reforming is more promising in terms of GHG reduction but it is still based on a finite fossil fuel. For a climatic sound provision of hydrogen as a fuel electricity from renewable sources of energy like wind or biomass should be used.

The gasification of biomass and the subsequent conversion to electric power, heat, or synthetic natural gas (SNG) offers the possibility to produce different products in one process under minimizing potential losses. In a so called polygeneration approach, the operation of such a process may be linked to changing energy market situations to improve the economic viability. The integration of water electrolysis for hydrogen production enables the process to provide positive as well as negative controlling power; i.e. it can provide system service and contribute to the stability to the electricity grid. Against this background, the aim of this paper is the technical, economic and environmental analysis of a polygeneration approach based on biomass gasification processes for the provision of SNG, heat and power taking the current electricity spot market into consideration. Therefore, several processes schemes are developed and analysed in terms of process efficiency (exergetic efficiency), economic viability (SNG production costs) as well as environmental performance (specific greenhouse gas emissions). For comparison, a biogas-based polygeneration approach for the production of biomethane, heat and power is analysed as well. In case of an operating mode optimised for SNG production, the exergetic efficiency results between 65.4 and 67.2 % for the gasification-based processes and 55.6 to 63.3 % for the biogas-based processes. If primarily electric power is provided in case of high spot market prices, the operation mode is optimised for power production; this results in significantly lower exergetic efficiencies of 48.0 to 44.9 % for the gasification-based processes and 38.0 to 41.2 % for the biogas-based processes. The production costs are calculated depending on the full load operating hours for maximizing SNG production and maximised power production, respectively. The results show a clear dependency of SNG production costs from the operating hours for all processes. The GHG emissions for maximum SNG production range between 43.4 and 95.1 gCO2-eq/kWhMethane. If more power is produced, the emissions rise to values between 55.4 and 127.6 gCO2-eq/kWhMethane. Lower emissions can be achieved by SNG production via gasification than via biogas.

Abstract Renewably produced hydrogen offers a solution for mobility via fuel cell electric vehicles without emissions during driving. However, the hydrogen supply chain, from hydrogen production to the fueling station – incorporating seasonal storage and transport – varies in economic and environmental aspects depending on the technology used, as well as individual conditions, such as the distance between production and demand. Previous studies have focused on the economic aspects of varying technologies and elaborated application areas of each technology, while environmental issues were not specifically considered. To address this shortcoming, this paper presents a life cycle assessment of three supply chain architectures: (a) Liquid Organic Hydrogen Carriers (LOHCs hereinafter) for transport and storage; as well as (b) compressed hydrogen storage in salt caverns, together with pipelines; and (c) pressurized gas truck transport. The results of this study show that the pipeline solution has the least environmental impact with respect to most of the impact categories for all analyzed cases. Only for short distances, i.e., 100 km, is truck transport better in a few impact categories. When considering truck transport scenarios, LOHCs have higher environmental impacts than pressurized gas in seven out of 14 impact categories. Nevertheless, for longer distances, the difference is decreasing. The seasonal storage of hydrogen has almost no environmental influence, independent of the impact category, transport distance or hydrogen demand. In particular, strong scaling effects underlie the good performance of pipeline networks.

Abstract One option to transport hydrogen over longer distances in the future is via Liquid Organic Hydrogen Carriers (LOHC). They can store 6.2 wt% hydrogen by hydrogenation. The most promising LOHCs are toluene and dibenzyltoluene. However, for the dehydrogenation of the LOHCs – to release the hydrogen again – temperatures above 300 °C are needed, leading to a high energy demand. Therefore, a Life Cycle Assessment (LCA) and Life Cycle Costing are conducted. Both assessments concentrate on the whole life cycle rather than just direct emissions and investments. In total five different systems are analysed with the major comparison between conventional transport of hydrogen in a liquefied state of matter and LOHCs. Variations include electricity supply for liquefaction, heat supply for dehydrogenation and the actual LOHC compound. The results show that from an economic point of view transport via LOHCs is favourable while from an environmental point of view transport of liquid hydrogen is favourable.

Abstract This paper presents a review of 32 Life Cycle Assessment studies on Power-to-X. Due to their multiplicity, different Power-to-X chains are compared and influencing factors on environmental impacts are identified. Besides technological specifications, methodological choices of the publications are assessed. The majority of studies consider Power-to-Gas or Power-to-Transport. Additionally, six publications assess Power-to-Power, Power-to-Liquids or Power-to-Chemicals. Climate change is the most analyzed environmental impact category. Further impacts are assessed in 14 publications. The electricity source and the methodological concept of carbon dioxide consideration are crucial drivers of environmental impacts. The review reveals a lack of transparency on technological as well as on methodological level. Specifications like the multi-functionality approach used or in case of Power-to-Transport chains the life time mileage of vehicles are missing in most publications and hinder their comparability.

The goal of this work was to study the assessment of the life cycle of hydrogen production from biomass for transportation purposes concerning greenhouse gas emissions, emissions with an acidification potential and the fossil energy demand. As feedstocks woody biomass from forestry or short rotation coppice, herbaceous biomass (i.e., straw), energy crops (mainly maize and grain), bio-waste and organic by-products (e.g., glycerol) were considered and their potential in Germany assessed. The results showed that hydrogen produced from woody biomass emitted the least emissions due to the low emissions caused by the provision of the biomass. Regarding the cumulative fossil energy demand biomass from short rotation coppice showed the lowest values. The highest biomass potential for hydrogen production could be identified for woody biomass from forests as well as from short rotation coppice.

Implementing hydrogen as a transportation fuel in an environmentally sound way necessarily requires a sustainable concept for the provision of the hydrogen used as a fuel. However, there are various possibilities for generating hydrogen from renewable and fossil sources of energy. For example, hydrogen production from wind energy or solar radiation via electrolysis or from biogas via steam methane reforming are methods currently under discussion. However, there are many other provision chains, and the environmental performance of such chains is significantly influenced by their design, that is, the location and type of hydrogen production, the distances involved, and the pressure for hydrogen transportation. Therefore, the overall goal of this chapter is to assess different possible hydrogen supply chains for greenhouse gas (GHG) emissions from a life cycle perspective. Additionally, the sensitivity of the GHG emissions to the design of the provision chain (e.g., transportation distances, location of the production facility) will be assessed. Different framework conditions, such as electricity or feedstock provision, are also analyzed. Based on these variations, promising hydrogen provision chains with minimized GHG emissions will be identified for the mobility sector.