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    Item type:Publication, Access status: with files ,
    Hydrogen supply chains for mobility : environmental and economic assessment
    (Multidisciplinary Digital Publishing Institute (MDPI), 2018-05-23)
    Wulf, Christina
    ;
    Kaltschmitt, Martin
    Hydrogen mobility is one option for reducing local emissions, avoiding greenhouse gas (GHG) emissions, and moving away from a mainly oil-based transport system towards a diversification of energy sources. As hydrogen production can be based on a broad variety of technologies already existing or under development, a comprehensive assessment of the different supply chains is necessary regarding not only costs but also diverse environmental impacts. Therefore, in this paper, a broad variety of hydrogen production technologies using different energy sources, renewable and fossil, are exemplarily assessed with the help of a Life Cycle Assessment and a cost assessment for Germany. As environmental impacts, along with the impact category Climate change, five more advanced impact categories are assessed. The results show that from an environmental point of view, PEM and alkaline electrolysis are characterized by the lowest results in five out of six impact categories. Supply chains using fossil fuels, in contrast, have the lowest supply costs; this is true, e.g., for steam methane reforming. Solar powered hydrogen production shows low impacts during hydrogen production but high impacts for transport and distribution to Germany. There is no single supply chain that is the most promising for every aspect assessed here. Either costs have to be lowered further or supply chains with selected environmental impacts have to be modified.
    Publicationtype: Journal Article
    Scopus© Citations 75  662  621
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    Item type:Publication, Access status: without files ,
    Assessment of selected hydrogen supply chains-factors determining the overall GHG emissions
    (Elsevier, 2018-01-01)
    Rödl, Anne
    ;
    Wulf, Christina
    ;
    Kaltschmitt, Martin
    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.
    Publicationtype: Book Part
      55
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    Item type:Publication, Access status: without files ,
      208
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    Item type:Publication, Access status: without files ,
    Polygeneration of SNG, heat and power based on biomass gasification and water electrolysis—concepts and their assessment
    (2015)
    Wagner, Hannes
    ;
    Wulf, Christina
    ;
    Kaltschmitt, Martin
    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.
    Publicationtype: Journal Article
      62
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    Life cycle assessment of biohydrogen production as a transportation fuel in Germany
    (Elsevier, 2013-08-30)
    Wulf, Christina
    ;
    Kaltschmitt, Martin
    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.
    Publicationtype: Journal Article
    Scopus© Citations 55  65