Browsing by Subject "Umweltbilanz"

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Life cycle assessment of perennial cultivation systems : advancing applicability and comprehensiveness
(2021) Lask, Jan; Lewandowski, Iris
Resource-efficient perennial cultivation systems are considered promising sources of sustainably produced biomass to meet the growing demand of a future European bioeconomy. They require fewer agricultural procedures than annual systems, contribute to an increase in soil carbon sequestration and can be productive on marginal land. In Europe, the C4 grass miscanthus is the most prominent and best researched perennial crop for lignocellulosic biomass production. Recently, wild plant mixtures (WPM) have been suggested as a more diverse alternative system. Perennial cultivation systems have already been the subject of multiple sustainability assessments, with life cycle assessment (LCA) being the method most commonly used. This method aims to provide a holistic depiction of the environmental performance of a system. However, two challenges are usually encountered. First, results of agricultural LCAs very much depend on site- and management-specific characteristics. Parameters such as biomass yield, quantity of fertiliser applied and carbon sequestered can vary considerably, impairing the applicability of the method. Second, most of these studies focus on greenhouse gas emissions only. Land use impacts on biodiversity are commonly neglected, casting doubt on the comprehensiveness that LCA is trying to achieve. This thesis aims to advance the applicability and comprehensiveness of LCA of perennial cultivation systems. For this purpose, it focuses on three aspects relevant to the assessment of such systems, each of which was addressed by a dedicated research question: 1) How can the conducting and application of LCAs of perennial cultivations systems be simplified? 2) Which methodological approaches are best suited for the consideration of carbon sequestration and storage in LCAs of perennial cultivation systems? 3) How can land use impacts of perennial cultivation systems on biodiversity best be incorporated into the LCA framework? These questions were answered by applying the LCA method to perennial cultivation systems in three case studies, using specific approaches for the inclusion of sensitivity analysis and the evaluation of carbon sequestration and storage. In addition, information on the biodiversity impacts of perennial crop cultivation was collated by means of a meta-analysis which compared species richness and abundance in annual and perennial crop cultivation systems. Due to the variability of agricultural systems, the life cycle inventory phase can be quite intricate. Thus, the conducting of an LCA can be substantially simplified by focusing on a few relevant inputs and outputs only. In this thesis a global sensitivity analysis was used to identify the most important inventory parameters in the greenhouse gas assessment of miscanthus cultivation: carbon sequestration, biomass yield, length of the cultivation period, nitrogen and potassium fertiliser application, and the distance over which the harvested biomass is transported. Focusing on these inventory parameters, a simplified model was developed. It allows farmers and SME active in miscanthus-based value chains easy access to customised LCA results. This thesis includes a detailed analysis of the relevance of carbon sequestration and storage in the sustainability assessment of perennial cultivation systems. It was found that the quantity and in particular the permanence of carbon sequestered through the cultivation of perennial crops are critical for their favourability in terms of global warming impacts. Two alternative methodological approaches for the quantification of carbon sequestered were tested within two of the case studies – a simple carbon model and an allometric approach. In addition, the handling of the uncertain permanence of the carbon storage was reflected upon. The approaches were compared with regard to their suitability for use by typical LCA practitioners. It was concluded that allometric models should be used for the quantification of carbon sequestered and the corresponding amount accounted for as delayed emissions. This combination provides a manageable approach for the accounting of benefits from carbon sequestration and storage, and also prevents their overestimation. Established impact assessment methods such as ReCiPe2016 suggest characterisation factors for the incorporation of land use impacts on biodiversity into LCA. These factors use relative species richness as an indicator and assume a higher species richness in perennial than annual cultivation systems. This thesis includes a critical review of these characterisation factors, drawing on the results of the meta-analysis comparison of species richness in annual arable crops and perennial rhizomatous grasses. The meta-study did not confirm a higher number of species in perennial rhizomatous grasses than in annual arable crops. It was concluded that LCA studies on perennial cultivation systems need to be cautious in their application of the land use characterisation factors suggested in present-day impact assessment methods. Criticisms of the approach include the application of one single characterisation factor for diverse perennial cultivation systems such as WPM and miscanthus and the sole focus on species richness. In future, LCA research should focus on context-specific adjustment options for land use characterisation factors to ensure an adequate representation of biodiversity impacts in agricultural LCAs. Finally, the current focus on species richness in biodiversity impact assessment needs to be reassessed.
Methodological approaches for assessing the environmental performance of perennial crop-based value chains
(2017) Wagner, Moritz; Lewandowski, Iris
In a developing bioeconomy, the demand for biomass for industrial purposes is expected to increase significantly. This demand needs to be met in a sustainable way and without compromising food security. With this goal in mind, resource-efficient lignocellulosic crops, such as perennial energy grasses, are often cited as a biomass source with low negative impacts on the environment. Under European conditions, miscanthus is the leading perennial energy grass because of its high biomass and energy yield potential. It is a C4 plant, which achieves dry matter biomass yields of up to 20 Mg ha−1 yr−1 when harvested in later winter, and up to 30 Mg ha−1 yr−1 when harvested green in October. Currently the main utilization route of miscanthus is direct combustion for heat generation, but the biomass can also be used for various other applications, such as biofuels and insulation material. Several studies have analysed the environmental performance of perennial crop-based value chains, but most of these only assessed the Global Warming Potential (GWP). However, the GWP alone is not an adequate indicator for the holistic assessment of the environmental performance of such value chains. In addition, these studies often used generic data and applied varying assumptions, which makes a comparison of different value chains difficult. The main goal of this thesis is to draw up recommendations for future assessments of the environmental performance of perennial crop-based value chains. For this purpose, five research objectives were formulated: 1) to identify the key parameters influencing the environmental performance of perennial crop-based value chains; 2) to analyse which impact categories are most relevant when assessing the environmental performance; 3) to assess the differences between various perennial-crop based value chains; 4) to assess the environmental performance of the utilization of marginal land to grow perennial crops for industrial purposes; and 5) to analyse and compare the environmental performance of annual and perennial crops in the example value chain ‘biogas production’. To achieve these research objectives, the environmental performance of several perennial crop-based value chains was analysed in various impact categories applying the same underlying assumptions and using field data obtained under ceteris paribus conditions. The analysis was carried out using the globally recognised Life Cycle Assessment (LCA) methodology, which is standardized by two ISO norms (14040/44). The results revealed that biomass yield is one of the most important parameters influencing the environmental performance of perennial crop-based value chains. An increase in yield of 50%, for instance, leads to an increase in carbon mitigation potential in a comparable range (46%). Furthermore, the marked influence on the environmental impact mitigation potential of both fertilizer-induced emissions and selection of the reference system was demonstrated. For example, if the reference system is changed from light fuel oil to natural gas, the substituting by heat generated from the combustion of miscanthus biomass increases the net impact in the category ‘particulate matter formation’ by 220%. The relevance of different impact categories was analysed for various perennial crop-based value chains using a normalisation approach. The results clearly indicated that a holistic assessment of the environmental performance of perennial crop-based value chains should at least include the impact categories ‘marine ecotoxicity’, ‘human toxicity’, ‘agricultural land occupation’, ‘freshwater eutrophication’ and ‘freshwater ecotoxicity’. In future assessments, it is recommended to include the impacts of land-use on both biodiversity (using species richness as an indicator) and soil quality (using SOM as an indicator). The comparison of the environmental performance of different perennial crop-based value chains revealed clear environmental advantages of the cascade use of biomass. An example is the production of miscanthus-based insulation material, which is first used as a building material and then incinerated to generate heat and electricity. The results also demonstrate that, despite low biomass yield on marginal land, miscanthus-based value chains have a substantial environmental impact mitigation potential when substituting a fossil-based reference system. Furthermore, the comparison of annual and perennials crops as biogas substrates showed that perennial crops, and in particular miscanthus, have a considerably better environmental performance in the impact categories ‘climate change’ (up to -73%), ‘fossil fuel depletion’ (up to -79%), ‘freshwater eutrophication’ (up to -69%), ‘marine eutrophication’ (up to -67%), and ‘terrestrial acidification’ (up to -26%). In all four studies included in this thesis, it was observed that the data used for the biomass cultivation in particular, such as yield and fertilizer-induced emissions, have a considerable influence on the environmental performance. This data is highly site- and crop-specific and is strongly dependent on the agricultural management system applied. Based on the results of this thesis, the common practice of using generic data in assessments of the environmental performance of perennial crop-based value chains should be rejected. In order to obtain realistic results, the use of site- and crop-specific data is highly recommended.
Die Ökobilanz zur Abschätzung von Umweltwirkungen in der Pflanzenproduktion - dargestellt anhand von Praxisversuchen zur konservierenden Bodenbearbeitung und von unterschiedlich intensiv wirtschaftenden konventionellen Betrieben
(2003) Arman, Beate; Claupein, Wilhelm
In the agricultural field difficulties in life-cycle assessment result from the fact that the methods of life-cycle assessment were developed in techno-industrial production. Agricultural production, however, differs from industrial production in that it depends more strongly on natural resources and, moreover, has a direct influence on them. Hence, apart from preparing data for the used production goods, the expansion of environmental impact categories to include specific effects from agriculture is focused on in the adaptation of ecobalances as an agricultural method. Among others deficiencies here include the balancing of effects in agriculturally utilized soil. The ecobalances at hand were carried out with two different goals in mind. For one, the impact of conventional and conservational cultivation methods were to be balanced. The goal of this ecobalance was to show whether life-cycle assessment have adequate selective power in order to be used as a decision criterion in the optimisation of cultural methods and their environmental impact. For another, the intensity of cultivation of three agricultural enterprises was compared. It was to be shown here whether life-cycle assessment can provide transparency as to the environmental effects of various production methods, which would enable the consumer to obtain information on the environmental relevance of these methods. A further goal of this work was the development of a method for the recording of effects on the soil in life-cycle assessment. The examined farms are situated in the Hohenlohe region and were integrated in the subproject "Conservation Tillage" of the "Cultural Landscape Hohenlohe" project group. In order to balance soil working methods, the three methods plow, cultivator and mulch sowing were examined. The data was obtained from two test fields with the same crop rotation on one of the farms. Balancing of the intensity of cultivation was carried out on three conventionally working farms using varying levels of fertilizer, crop protectants and tillage. The balanced crop rotation of the three farms did not vary (sugar-beets, winter wheat, winter barley). When developing methods for balancing environmental effects on agriculturally utilized soil three aspects were decisive in the selection of balanced effects: 1. What soil properties are there? 2. Which of these properties are influenced directly by cultivation measures? 3. For which properties are relevant negative effects caused by agriculture known? Based on the indicated methods the impact was assessed for the following soil properties: - Soil depth is influenced by soil loss. Soil loss was calculated with the universal soil loss equation. - Impact on the nutrient content was assessed with the help of a nutrient field balance, humus content with the help of a humus balance. - Variations in soil density caused by loading were assessed with the help of the weighted soil load. - Soil life is affected by pollutant input, modelling of the effect potential was carried out with the help of the Critical-Surface-Time model. All in all the results show that in order to differentiate between the tillage variants with respect to their environmental impact, it is necessary to also consider effects on the soil. Comparison of the farms showed that life-cycle assessment can reflect the environmental relevance of different cultivation intensities and can make them visible for the consumer.
On the interplay of local versus global environmental and economic performance of Swiss alpine dairy farms
(2017) Repar, Nina; Doluschitz, Reiner
This cumulative dissertation consists of a general introduction (Chapter 1), three scientific papers (Chapters 2, 3 and 4) and a general conclusion (Chapter 5). The first peer-reviewed paper presented in Chapter 2 is of a conceptual nature. Based on a comprehensive and systematic review of the farm-level environmental performance indicators found in scientific literature, it shows that several of these indicators are inconsistently defined and inappropriate for the purpose of farm environmental performance assessment. This is due to the lack of conceptual considerations behind their definition. In the second step, starting from the environmental sustainability concept at macro level, the paper develops conceptual considerations on how to implement this concept at farm level into theoretically sound and consistent indicators of farm environmental performance. Based on the environmental sustainability concept viewed from an ecological perspective and on the associated ecosystem’s carrying capacity (constraint) concept, it distinguishes between the carrying capacity of the global ecosystem and that of the local ecosystem. Relying on this distinction, it proposes to differentiate between the global and local environmental performance of a farm. Whereas farm global environmental performance relates the cradle-to-farm gate (i.e. off- and on-farm) environmental impacts to the biophysical farm output, farm local environmental performance focuses on local on-farm environmental impact generation and relates it to the local on-farm area. The second peer-reviewed paper (Chapter 3) consists in an empirical application of the framework developed in Chapter 2. This application was carried out for a sample of 56 Swiss dairy farms, for which very detailed and comprehensive cradle-to-farm gate life cycle assessments (LCAs) were conducted. Farm global environmental performance was assessed as the farm digestible energy output for humans per unit of cradle-to-farm gate environmental impact. Farm local environmental performance was measured by the on-farm land area per unit of on-farm environmental impact. The paper investigates the relationships within the environmental performance dimension (i.e. between farm global and local environmental performance), and between the environmental and economic performance dimensions. The results showed the complexity of the relationships between farm global and local environmental performance. Trade-offs occurred more frequently than synergies, implying that an improvement in farm global environmental performance regarding one environmental issue will likely lead to a deterioration in farm local environmental performance regarding at least one other issue, and vice versa. These trade-offs highlight the challenging and complex nature of the improvement of the environmental sustainability of farming and provide clear evidence that farm environmental performance cannot and should not be reduced to a single “one size fits all” indicator. Our work furthermore showed the existence of synergies between farm global environmental and economic performance. The third peer-reviewed paper (Chapter 4) relies on the same dataset as used in Chapter 3. It investigates different structural, farm management, socio-demographic, technological and natural-environment-related determinants of the economic and environmental performance of dairying. It aims to identify the factors with the potential to simultaneously improve farm global environmental, local environmental and economic performance. The results revealed the existence of some factors presenting synergies and several factors showing trade-offs in the enhancement of these three dimensions of the sustainable performance of a farm. Organic farming, higher agricultural education level of the farm manager, the production of silage-free milk, and also, however to a weaker extent, full-time farming, larger farm size and a lower intensity of cattle concentrates use were identified as factors that allow global environmental, local environmental and economic performance to be improved simultaneously. More generally, the promotion of farm global environmental performance and farm economic performance was shown to be synergetic whereas the enhancement of farm global and local environmental performance turned out to be mostly antinomic. The core implications and related recommendations derived from the findings of this work are twofold. First, the conceptually correct measurement of farm environmental performance imperatively requires (i) the separate implementation of global and local environmental performance indicators as proposed in the framework and (ii) the consideration of both global and local dimensions to avoid environmental problem shifting from local to global scale and vice versa. This is especially necessary as the empirical application for Swiss alpine dairy farming found several trade-offs between farm global and local environmental performance. This empirical finding has far-reaching implications, especially if it is to be confirmed for other types of farms and other countries. The second core finding of this dissertation relates to the possibilities for improving the environmental and economic sustainability of Swiss alpine dairy farming. This work showed that there are some factors, namely organic farming, higher agricultural education level of the farm manager, the production of silage-free milk, and also, however to a weaker extent, lower intensity of concentrates use, larger farm size and full-time farming, which allow farm global environmental, local environmental and economic performance to be improved simultaneously.
The potential of miscanthus as biogas feedstock
(2020) Kiesel, Andreas; Lewandowski, Iris
Of all renewable energy forms, biomass accounts for the by far largest proportion of gross inland energy consumption in Europe. As the biogas sector in particular can provide demand-driven electricity generation, energy storage and flexible utilization options including biofuels, it is likely to play an important role in future energy systems in future. In Germany, the largest biogas market in Europe, energy crops provide the highest proportion of biogas input substrates, with maize being the most dominant. The environmental impact of biogas production is mainly attributed to energy crop production, with the risks of maize cultivation being particularly criticized. Perennial biomass crops have the potential to reduce the environmental impact of the biogas sector and miscanthus is an especially promising candidate crop due to its high yields. However, preliminary observations have indicated that the green harvest of miscanthus necessary for biogas production leads to a strong yield depression in the subsequent year. The aim of this thesis was to determine and understand the mechanisms influencing the green-cut tolerance of miscanthus and to assess the potential of different green-harvest regimes for biogas production. Here, ‘green-cut tolerance’ is defined as the crop’s ability to regrow in the year after the green harvest is performed without yield depression. A further aim of this thesis was to investigate the environmental performance of miscanthus-based biogas production and to determine its energy efficiency compared to other utilization options. Field trials were conducted to assess the potential of miscanthus hybrids for biogas production, the green-cut tolerance of Miscanthus x giganteus (Mxg), and how both are influenced by management practices (harvest regime x nitrogen fertilization). A Life-Cycle Assessment was performed to evaluate the environmental impact of biogas production from perennial C4 grasses, including miscanthus, and to assess the optimization potential compared to the standard biogas crop maize. The suitability of miscanthus biomass was investigated for the utilization options bioethanol, biogas and combustion, and the energy efficiency of these was compared based on their net energy yield. The results revealed that Mxg harvested in October showed the highest average biomass yield, the highest methane yield (approx. 6000 m3 methane ha-1) of all harvest regimes, and a higher substrate-specific methane (SMY) yield than for biomass harvested after winter. An earlier green harvest (July, August) improved the SMY, but led to a sharp biomass and thus methane yield decline in the second year and was identified as unsuitable for Mxg. As increased nitrogen fertilization showed no effect on the yield in any of the harvest regimes, it can be disregarded as a management practice for improving green-cut tolerance. Instead, harvest date was found to have a strong influence on green-cut tolerance and sufficient time for relocation of carbohydrates needs to be allowed before a green cut is performed. This finding is crucial for the utilization of miscanthus biomass harvested green and also for the breeding of new varieties with improved green-cut tolerance. Breeding targets for optimized biogas varieties should include to increase the SMY and biomass yield and to widen the possible harvest window. Selecting genotypes that relocate carbohydrates to the rhizomes earlier would allow an earlier green harvest without yield decline the following year, but this may involve a trade-off with the SMY. The suitability of miscanthus for the utilization options assessed was found to be influenced by biomass composition, which in turn was affected by genotype and harvest date. Lignin content had a negative effect on biomass quality for biogas and bioethanol production and increased with later harvest dates. Hemicellulose had a positive effect on biomass quality for bioethanol production through the improvement of the saccharification potential. Low ash, potassium and chloride content enhanced biomass quality for combustion by increasing the ash melting temperatures and decreased with a delay in harvest to after winter. For the biogas and bioethanol utilization pathways, novel miscanthus varieties with low lignin content need to be developed, whereas for combustion varieties with a high lignin content are more favourable. The Life Cycle Assessment revealed that the use of miscanthus has a high potential to reduce the environmental impacts of biogas crop production and thus the biogas sector. Miscanthus had a more favourable performance than the annual biogas crop maize in each impact category considered and the highest reduction potential compared to the fossil reference in the impact categories climate change, fossil fuel depletion and marine eutrophication. The choice of biomass utilization pathway had a considerable effect on the energy yield per unit area, with combustion showing the overall highest energy yield potential for electricity production. However, for the combustion pathway, miscanthus is generally harvested after winter and this is accompanied by biomass yield losses of 35% compared to peak yield. In the biogas pathway, miscanthus can be harvested close to peak yield, leading to an only 10% lower energy yield than that of combustion. When considering the use of miscanthus for biofuel production, the highest area efficiency was found for the direct use of biomethane, followed by battery electric vehicles fuelled by electricity from biomass combustion, and the lowest for the direct use of bioethanol. However, the low conversion efficiency of bioethanol production did not consider energy generation from by-products. In this thesis it was determined that the green-cut tolerance of miscanthus is influenced by the carbohydrate relocation to the rhizomes and thus by harvest date. Miscanthus harvested in October shows a high potential as feedstock for biogas production due to its high yield and sufficient digestibility, can help improve the biogas sector’s environmental performance and contribute to an increase in greenhouse gas mitigation. The digestibility of miscanthus biomass for biogas production could be improved by breeding and selecting genotypes with low lignin contents and by applying suitable pretreatment methods. Increased digestibility could also help to overcome potential trade-offs between early carbohydrate relocation and SMY. The efficiency of biomass utilization greatly depends on the utilization option, with a high efficiency being identified for biomethane as a transportation fuel and for peak-load power generation. It was shown that miscanthus is a suitable crop for the provision of sustainably produced biomass as a feedstock for the growing European bioeconomy that provides additional ecosystem services, e.g. groundwater and surface water protection.
Verbesserung der Energie-, Stoff- und Emissionsbilanzen bei der Bioethanolproduktion aus nachwachsenden Rohstoffen
(2010) Fleischer, Sven; Senn, Thomas
In this thesis, a process was realized that uses starchy raw material (triticale) as well as lignocellulosic biomass (corn silage) in one ethanol production process. In contrast to other so called 2nd generation ethanol processes, which only use lignocellulosic material, the problem of the very low potential ethanol concentration (