Browsing by Subject "Bioenergie"

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Agrofuels, large-scale agricultural production, and rural development : the case of Jatropha in Madagascar
(2019) Bosch, Christine; Zeller, Manfred
Agrofuel production in marginal areas can contribute directly to creating employment and improving local livelihoods. Indirectly, through increasing household purchasing power and relaxing financial constraints of smallholder farmers, it can contribute to greater food production and/or food consumption and rural development. These benefits depend, however, largely on the feedstock crop and its processing, land and labour requirements, the business model, value chains and institutional frameworks. Jatropha, a feedstock crop with more benefits than first-generation energy crops like maize, experienced a spike in popularity in the early 2000s due to its value in the biofuel markets of industrialized countries. The majority of plantations and outgrower schemes could not survive what followed: disappointing yields, pests and disease, low oil prices, the 2007/2008 food price crisis, negative narratives, and inadequate funding for further research activities. Despite these challenges, large-scale land investments and new Jatropha projects continue to be undertaken. Madagascar is a country characterized by severely eroded and degraded pasturelands, low agricultural productivity, high vulnerability to climatic shocks, and overwhelming poverty and food insecurity rates. It is hypothesized that the use of marginal lands for labour-intensive agrofuel feedstock cultivation, in otherwise neglected areas, through both public and private investment, will have positive impacts through the provision of wage work in large-scale plantation schemes. Although a number of studies have investigated the rural livelihood impacts of participation in Jatropha cultivation, there is little evidence that quantifies the long-term and indirect effects on smallholder food production and household food security. Against this background, large-scale Jatropha cultivation lends itself well to studying the complex interplay between feedstock and food production, as well as the potential for agricultural and rural development. Such analysis would provide useful insights and implications for cost-effective rural development policies to target poor farmers in remote areas. Drawing on a conceptual framework that highlights the role of smallholder farmers’ livelihood strategies like off-farm employment and agricultural intensification, and livelihood outcomes like food security, this thesis explores the contribution of large-scale agrofuel feedstock cultivation on marginal land. Three important outcomes, namely household food security, information and innovation spillover effects, and agricultural input use, are studied empirically in three articles, using a comprehensive household panel data set. The data was collected in six survey rounds between 2008 and 2014, in three villages near a large-scale Jatropha project in the Haute Matsiatra region, located in Madagascar’s Southern Highlands. The first article examines the relationship between wage work for a Jatropha project and household food security. Jatropha cultivation on marginal land is labour intensive and does not compete with food production. Therefore, incomes earned can contribute to increased food security directly as well as indirectly through increased or diversified food production. Using five rounds of household panel data, results show that labour demand from the plantation declined substantially after the build-up phase and Jatropha incomes were mostly used for food and other necessities. Fixed effects models show that Jatropha work contributed significantly to an improved dietary diversity. Despite the possibility to earn income during the lean season, Jatropha work did not lead to a reduction in the more subjective lack of food and led to reduced rice stocks. Both food production and consumption were highly influenced by drought shocks and locust plagues, indicating that complementing income creation strategies with agricultural development strategies might have further positive effects on food security. To shed light on the impact pathway from Jatropha work to agricultural production, the second article explores information dissemination through social networks and through Jatropha workers who are more exposed to modern technologies than control households. In addition to institutional factors, a lack of knowledge and limited extension services for improved agricultural technologies are considered barriers to information dissemination. Using two rounds of the dataset, which contains rich information on social capital and networks as well as knowledge and innovations, determinants of production-relevant knowledge like extension services, credit and marketing opportunities are estimated. Accounting for potential endogeneity with lagged and instrumental variables, the relevance of this knowledge to the adoption of innovations and the cultivation of a formerly taboo legume, as an example of diversification, is tested. The results indicate limited access to information, little knowledge on investment and marketing opportunities, and low adoption of innovations. Knowledge is relevant for both innovation performance and the cultivation of the Bambara groundnut, highlighting the need to increase and improve public extension services and information dissemination in rural Madagascar. Adoption is not only encouraged by knowledge, but also directly motivated through informal social networks. Bambara groundnut spillovers from the biofuel project can be observed, relaxing some of the constraints farmers face concerning access to information, social learning, and cultural norms. The third article explores one specific hypothesized spillover: access to and use of agricultural inputs. Given the very low use of improved inputs in rural areas in Madagascar, this study explores whether improved seed and seed information distributed to farmers encourages farmers to cultivate the seed. The analysis is based on household data gathered between 2012 and 2014 from 390 households in three villages. To investigate the adoption of improved seed, as well as the diffusion of information regarding improved seed, a randomized control trial was applied in 2013. Half of the 390 households were randomly assigned to receive the improved lima bean seed (Phaseolus lunatus), which is specifically bred for dry regions. Of the seed-receiving households, half were randomly assigned to receive information on how to store, plant, and cultivate the improved seed, as the variety was unfamiliar in the region. The control group and the two treatment groups are compared with respect to baseline characteristics, bean cultivation, information exchange with other farmers, legume consumption, and willingness to pay (WTP) for improved bean seed. To account for non-compliance, contamination, and spillover effects, local average treatment effects (LATE) are estimated. Of the seed-receiving households, 54% cultivated the seed, reaping an average yield of 6.3 kg for each kilogram of seed obtained. Seed information did not lead to higher yields. A small significant positive impact of seed distribution on legume consumption is found. WTP is 171% of the local market price for bean seed; provision of free seeds and information did not result in a higher WTP. Based on these findings, this thesis contributes empirical evidence that large-scale agrofuel feedstock production on marginal land can enhance rural livelihoods by offering alternative livelihood strategies especially for poorer households and contributing to improved livelihood outcomes. Accounting for the indirect effects shows important impact pathways on the livelihood strategies of farmers in a remote area. The provision of incentives for private investors, complemented by more public intervention in rural areas, as well as more investment in agricultural research and extension to reduce agricultural production risks, might enhance these spillovers.
Biomass production for bioenergy as an interface between yield optimisation, ecology and human nutrition : a question of resource efficiency
(2012) Gauder, Martin; Claupein, Wilhelm
In this thesis, specific questions dealing with sustainability of bioenergy were analysed on regional scales. One focus was put on food security and the connections to bioenergy production. Therefore a study, based on the comprehensive range of information available, was conducted for ethanol production in Brazil. The second focus laid on Europe and the potentials and environmental risks which come along with bioenergy production. A study on interannual yield performance of long-term Miscanthus plantations was conducted to evaluate potentials and genotype diversities of Miscanthus cropping in Southwest Germany. To identify the possible contribution of by-products from agriculture, a third study dealt with amount and distribution of surplus straw in Southwest Germany. Environmental aspects were addressed in a field trial, which monitored trace gas fluxes from soils under different energy plants also in Southwest Germany. The last study examined the potential of establishing large-scale poplar plantations in Romania and how this could contribute to the regional energy security.
Biomethane production in an innovative two-phase pressurized anaerobic digestion system
(2015) Chen, Yuling; Jungbluth, Thomas
Generation of biogas from biomass through anaerobic digestion is receiving increasing attention. Over the past decade, the biogas industry has been developing rapidly in Germany, as well as the rest of the world. In Germany, biogas is generally used in a heat and power plant (CHP) for electricity and heat production. However, most biogas plants are located in a rural area, where heating demands are quite low. Except for biogas plant thermal control, a huge amount of cogenerated heat is often wasted. In order to increase the overall energy utilization efficiency, biogas can be alternatively converted to biomethane of natural gas quality and injected into existing gas grids. By making use of the mature gas transportation and storage systems, biogas production and end utilization can be temporally and spatially separated. Therefore, it is regarded as an efficient and flexible solution to energy issues. Nevertheless, in terms of this application, raw biogas requires, above all, gas purification and upgrading. Carbon dioxide content, in particular, must be reduced from 40–50% in the raw biogas to approximately 4% in the purified gas. Conventional technologies are generally expensive in investment and/or operation. Therefore, an economical option is desired. Within this research project, a two-phase pressurized anaerobic digestion system was developed. The innovative concept aimed to reduce the cost involved in biomethane conversion and injection into the natural gas grids by integration of biogas production, purification and compression in one system. It was expected that a great amount of carbon dioxide could be directly removed from the pressurized digester due to its high solubility. In addition, the methane-rich biogas could be produced at an elevated pressure which could meet the injection standard, and therefore could reduce or even avoid the expenses for further compression. In order to gain better understanding of two-phase pressurized anaerobic digestion, three major studies were conducted: - The pressure effects on two-phase anaerobic digestion - Effects of organic loading rate (OLR) on the performance of a pressurized anaerobic filter in two-phase anaerobic digestion - Effects of liquid circulation on two-phase pressurized anaerobic digestion By this means, the system performance could be examined and the technical feasibility and potential of the new concept could be explored. Moreover, an optimization of the process in a two-phase pressurized anaerobic digestion system could be realized. From both economic and ecological perspective, two-phase pressurized anaerobic digestion offers an interesting process option for biomethane production, making a great contribution to sustainable energy supply.
Comparative performance of annual and perennial energy cropping systems under different management regimes
(2007) Böhmel, Ute Constanze; Claupein, Wilhelm
The theme of this thesis was chosen against the background of the necessary substitution of fossil fuels and the need to reduce greenhouse gas emissions. One major solution for these topics may be the energy generation from domestically produced biomass. The overall aim of this thesis was the identification of one or more efficient energy cropping systems for Central Europe. The target was set to supply high quality biomass for existent and currently developing modern conversion technologies. Renewable energy production is thought to be environmentally benign and socially acceptable. The existence of diverse production environments necessitates further diversification and the identification of several energy crops and the development of energy cropping systems suited to those diverse environments. This thesis starts with an introductory essay (chapter 1), which provides the background for renewable energy production, its features, demands and potentials, and the scientific basis of this thesis. Chapters 2 to 6 consist of five manuscripts to be published in reviewed journals (Papers I, II, IV and V) or in a multi-author book (Paper III). Subsequently, the results from all papers are discussed in a general setting (chapter 7), from which a general conclusion is formulated (chapter 8). The basis of the research formed four field experiments, which were conducted at the experimental sites Ihinger Hof, Oberer Lindenhof and Goldener Acker of the University of Hohenheim, in south-western Germany. Paper I addresses the overall objective of this thesis. Selected cropping systems for this experiment were short rotation willow, miscanthus, switchgrass, energy maize and two different crop rotation systems including winter oilseed rape, winter wheat and winter triticale with either conventional tillage or no-till. The systems were cultivated with three different nitrogen fertilizer applications. An energy balance was calculated to evaluate the biomass and energy yields of the different cropping systems. Results indicate that perennial lignocellulosic crops combine high biomass and net energy yields with low input and potential ecological impacts. Switchgrass, which produced low yields at the study site, may better perform on marginal sites. Switchgrass is an example of the need to grow site-adapted energy crops. The annual energy crop maize required the highest input, but at the same time yielded the most. The two crop rotation systems did not differ in yield and energy input, but the system with no-till may be more environmentally benign as it has the potential to sequester carbon. The objective of Paper II was the optimization of crop cultivation through the differentiation of input parameters to enhance the quality of the energy crop triticale, without influencing the biomass yield. The intention was to minimize the content of combustion-disturbing elements (potassium and chlorine) and the ash residue of both aboveground plant parts (grain and straw). It was done through different straw and potassium fertilizer treatments. It could be shown that the removal of straw from the previously cultivated crop and no additional potassium fertilizer could reduce the amount of combustion-disturbing elements. A high influence must also be expected from site and weather conditions. Papers III to V address the supply of different high quality biomasses, with the focus on maize for anaerobic digestion. The objective of Paper III was the assessment of the requirements of biogas plants and biomass for anaerobic digestion. It introduces potential energy crops, along with their advantages and disadvantages. Alongside maize, many other biomass types, which are preserved as silage and are high in carbohydrates and low in lignocelluloses, can be anaerobically digested. The development of potential site-specific crop rotation systems for biomass production are discussed. The objective of Papers IV and V was the identification of suitable biomass and production systems for the anaerobic digestion. The focus lay on the determination of (i) suitable energy maize varieties for Central Europe, (ii) optimal growth periods of energy crops, (iii) the influence of crop management on quality parameters and (iv) environmentally benign crop rotation systems. Differently maturing maize varieties were grown in six different crop rotation systems (continuous maize with and without an undersown grass, maize as a main crop partially preceded by different winter catch crops and followed by winter wheat) and tested at two sites. Additional factors were sowing and/or harvest dates. Maize and cumulative biomass yields of the crop rotation systems were compared. Specific methane yield measurements were carried out to evaluate the energy performance of the tested crops. Quality was assessed either by measurements of the dry matter content or by using the near infrared reflectance spectroscopy for the determination of chemical composition. Results indicate that an environmentally benign crop rotation system requires nearly year-round soil cover to minimize nitrogen leaching. This can be achieved through the cultivation of undersown or catch crops and additional main crops alongside maize, such as winter wheat. Late maturing maize varieties can be cultivated at a site where the maize can build adequate dry matter contents due to a long growth period (late harvest date). The energy generation in terms of methane production was primarily dependent on high biomass yields. It could be further shown that the specific methane yield of maize increased with increasing starch content, digestibility and decreasing fiber content. To conclude, selected site-specific energy crops and crop rotation systems, with suitable crop management, (fertilizer and soil tillage) can produce high quality biomass and the highest net energy return. Lignocellulosic biomass can be optimized for combustion. Wet biomass is an optimal substrate for anaerobic digestion. Profitable energy production is characterized by a high land and energy use efficiency and especially high net energy yields.
Economy-wide policy modeling of the food-energy-water nexus : identifying synergies and tradeoffs on food, energy, and water security in Malawi
(2017) Schünemann, Franziska; Zeller, Manfred
Food, energy, and water are essential goods for human survival. The three goods are intrinsically connected through economic consumption and production linkages as well as ecological processes. All three are dependent on limited resources which are threatened by global drivers in the form of economic growth, population growth, and climate change that are particularly affecting developing countries. Therefore, a nexus perspective that simultaneously encompasses food, energy, and water has become crucial to avoid resource inefficiencies and to ensure the provision of the three goods for the most vulnerable people. This dissertation contributes to the research on the food-energy-water (FEW) nexus approach through first developing integrated modeling frameworks that capture the linkages between food, energy, and water, in order to secondly identify those policy measures that maximize the synergies for food, energy, and water security and minimize the tradeoffs. To this end, three studies analyze four policies – biofuels production, irrigation expansion, improved cookstoves and agroforestry – that directly affect food, energy, and water security and provide a large scope for realizing synergies. The empirical findings of this dissertation show that policy measures indeed produce some tradeoffs between FEW security, but that – if policies are designed correctly – the tradeoffs can be minimized while simultaneously maximizing the synergies. These findings are an essential contribution to the literature through proving that even in a world with enormous pressures on limited resources, prudent policy making can provide FEW security for all people. Finally, the results demonstrate that the development of integrated modeling frameworks is vital for quantitative analyses of policies that simultaneously affect the economic, social, and environmental spheres to identify the synergies and tradeoffs. This dissertation makes an important methodological contribution to integrated environmental-economic modeling of developing countries and may serve as a starting point for future research on linking the economy and the environment in models.
Fernerkundungsgestützte Analyse und Bewertung ökologischer Auswirkungen des Anbaus von Bioenergiepflanzen auf die Agro-Biodiversität anhand der Modellierung der Habitatansprüche der Feldlerche (Alauda arvensis)
(2017) Schlager, Patric; Schmieder, Klaus
For the first time in 2002, the transformation of the conventional energy system into a system based on renewable energies was politically and legally decided in Germany. On the regional level numerous communities and municipalities followed this decision by voicing their own political resolutions, addressing the coverage of energy consumption with renewable energies. Their implementation is accompanied by a spatial expansion of bioenergy crops which lead to a controversial discussion about food safety, biodiversity and landscape change. Framed by the above mentioned discussion, this study assesses potential changes of skylark (Alauda arvensis) occurrence caused by a spatial expansion of bioenergy crops in the municipality of Schwäbisch Hall, Germany. The skylark was selected due to the comprehensive state of research about skylarks, their endangerment (“Red list of German breeding birds”), and the status as umbrella species for open agricultural landscapes (skylarks typically avoid vertical structures like hedges or edges of forests). The latter emphasizes their role as representatives for other species which are potentially affected by an expansion of bioenergy crops. This study is based on a stratified bird monitoring scheme of Baden-Württemberg, which was developed during a project that aimed to set up an indicator for species richness and was financed by the Bundesministerium für Ernährung, Landwirtschaft und Verbraucherschutz (BMELV). From the bird monitoring scheme, the stratum, which covers the municipality of Schwäbisch Hall, was extracted and served as a base for the development of a Generalized Linear Habitat Model of the skylark. In order to assess potential habitat changes caused by an expansion of bioenergy crops, Schwäbisch Hall was mapped with an airborne remote sensing technology in 2011. The resulting aerial images were transformed into orthophotos and later classified (focusing on agricultural areas) with an object oriented image analysis approach. Based on the outcomes of the habitat association model and the land use classification, skylark territories were predicted for 1 km² plots covering Schwäbisch Hall. For an in-depth understanding of ecological impacts from expanded bioenergy cropping, a bioenergy scenario was developed considering § 17 BBodSchG (national soil protection act) and regional food security. Based on the scenario, skylark territories were predicted for 1 km² plots covering Schwäbisch Hall. The most reasonable habitat association model resulted in a negative binomial Generalized Linear Model with the predictors winter sown crops and mean patch size per plot. Model performance was assessed by Wald z-statistics with p-values, ANOVA, explained variance, theta, residuals, AIC, and independent field data. Field data was only available for one plot. Therefore, the field data only indicate model performance. The comparison of the model predictions with the field data resulted in an accuracy of 92.21%. The land use classification resulted in the following five classes: 1. winter sown crops (33985.78 ha), 2. maize (9621.36 ha), rapeseed (2952.36 ha), unidentified crops (7244.18 ha), and grassland (30720.88 ha). Grasslands were not mapped by remote sensing techniques, but taken from a digital landscape model. Accuracy assessment showed an overall accuracy of 89.16 % and 0.78 kappa statistics. Prediction of skylark territories based on the land use classification of 2011 resulted in 46269 territories, or a mean density of 8.4 territories per 10 ha on agricultural areas and 5.4 territories per 10 ha on agricultural and grassland combined areas. The scenario assumed a three partite crop rotation (maize, rapeseed, winter sown crops) and a mean value of 0.17 ha per inhabitant for food security. Areas for fodder production were considered in course of the calculation of food security because Schwäbisch Hall is characterized by many livestock farms, which made it necessary to avoid conflicts between potential bioenergy sites and areas for fodder production. Considering the above mentioned assumptions, Schwäbisch Hall has a bioenergy potential of 5955 ha for maize and 15033 ha for rapeseed cropping. The results of the bioenergy scenario were randomly distributed to the land use polygons which resulted from the remote sensing analysis. With that, prediction of skylark territories based on the bioenergy scenario was feasible. Skylark territories for the bioenergy scenario resulted in 36472 territories, or a mean value of 6.8 territories per 10 ha on agricultural areas and 4.3 territories per 10 ha on agricultural and grassland combined areas. Considering both land use options, skylark territories declined by 8797 in total numbers or by 19.43 % in relative numbers. In addition to the land use options described above, landscape structure and territory distribution were analyzed based on six landscape units (Naturräumliche Haupteinheiten) covering the municipality of Schwäbisch Hall. The analysis revealed an agriculturally dominated northwestern part, with high numbers and mean values of skylark territories, and a grassland/forest dominated southeastern part, with lower numbers and mean values of skylark territories. The relative decline of these territories between the two land use options within the landscape units resulted approximately in 22 % in the northwestern and approximately 11-15 % in the southeastern part. The results indicate that an expansion of bioenergy crops will have negative effects on breeding birds in open agricultural landscapes which already suffer from degraded habitat conditions. Based on the assumptions of this study, skylark territories will decline by approximately 20 % in comparison to 2011. Yet, considering the results of the indicator report of the German National Strategy on Biodiversity (BMU 2010) and the European Bird Census Council the baseline of 2011 already represents a degraded situation in terms of habitat quality for agricultural breeding birds.
How can miscanthus be integrated most efficiently into agricultural production systems?
(2019) Mangold, Anja; Lewandowski, Iris
The demand for biomass is increasing steadily, as fossil resources are gradually being replaced by biomass within the context of a developing bioeconomy. Plant-based feedstocks currently used for this replacement virtually all come from annual crops. However, perennial crops such as miscanthus are expected to be more environmentally benign due to their generally low-input requirements and high yield potential. Despite these advantages, the current cultivation area of miscanthus in Europe is quite low. One reason for this is that the cultivation and utilization of miscanthus faces several challenges. For example, the most common propagation method via rhizomes is very labour-intensive and thus expensive, leading to high establishment costs. Seed propagation is a promising option to reduce costs, but is not suitable for sterile genotypes. Another challenge to be overcome is the problem of re-integrating former miscanthus fields into crop rotations. The crop following miscanthus needs to be highly competitive in order not to be impaired by resprouting miscanthus shoots and thus able to achieve high yields. Additionally, there is only little information available on the effect of miscanthus cultivation and its subsequent removal on soil N content. This information is however crucial, for example to avoid environmental problems being caused by a potential nitrogen leaching after a miscanthus removal. If miscanthus is to be utilized as a biogas substrate, there are further challenges to be overcome. Firstly, the optimal harvest date needs to be defined with regard to the methane hectare yield and resilience of the crop to green cutting. Secondly, as a continuous supply of biomass throughout the year is necessary, ensiling will become a relevant topic. However, information is still required on the optimal harvest date to achieve a sufficient silage quality and the effects of ensiling on methane hectare yield. Finally, the suitability of miscanthus for biogas production is also influenced by biomass quality such as the proportions of leaf and stem. This has already been established for miscanthus utilization in combustion but has not yet been sufficiently investigated for anaerobic digestion. In summary, there are a number of uncertainties involved in miscanthus establishment, removal and utilization, which currently hamper its integration into agricultural production systems. From a bioeconomic point of view, this integration needs to be conducted as efficiently as possible in terms of nutrient-use, environmental and land-use efficiency. The aim of this study was to contribute to the filling of these knowledge gaps. To answer these knowledge gaps, several miscanthus field trials and laboratory experiments were conducted: a novel propagation method was tested; the re-integration of miscanthus fields into a crop rotation was analysed; and the effect of genotype, harvest date and ensiling on the digestibility and methane hectare yield was investigated. The results illustrate some possibilities of improving the nutrient-use, environmental and land-use efficiency of miscanthus biomass production along its supply chain: It was shown that miscanthus propagation via collars is feasible and a promising alternative to rhizome propagation, as the multiplication rate of collars is comparable to that of rhizome propagation. As the harvesting of collars is likely to be less labour-intensive and is less destructive for the mother field than rhizome propagation, this method is more favourable for both economic and ecological reasons. The re-integration of miscanthus into crop rotations revealed maize to be a suitable crop after miscanthus, as it coped with the prevailing soil conditions and suppressed resprouting miscanthus efficiently, resulting in satisfactory yields. The soil mineral nitrogen (Nmin) content was found to increase during the vegetation period following a miscanthus removal, but was generally on a low level (average: 17.3 kg Nmin ha-1). Additionally, it was found that, in Germany, miscanthus should be harvested in mid-October to maximize methane yields and nutrient recycling but minimize yield reduction. In addition, silage quality was best when miscanthus was harvested on this date. As leaf proportion correlated positively with substrate-specific methane yield (SMY) and thus genotypes with a higher leaf proportion were found to have a higher SMY, methane hectare yields could be increased even further by using genotypes with a high leaf proportion. In summary, the approaches developed in this study allow to considerably improve the ecological and economic performance of miscanthus production by increasing nutrient-use,environmental impact and land-use, and thus simplifying implementation into practice.
Nachhaltiger Anbau von Bioenergie : eine ökonomisch-ökologische Analyse für die Landwirtschaft in Baden-Württemberg
(2012) Konold, Angelika; Zeddies, Jürgen
The aim of this thesis is on the one hand to estimate the potential of energy crop production for CO2-sequestration in Baden-Württemberg. On the other hand the focus lies on the interactions that arise from the implementation of optimized na-ture conservation measures with the land management on regional level. For this the existing economic-ecological regional model EFEM (Economic Farm Emission Model), based on linear programming, is further developed. The calculations are made on farm level and are extrapolated on regional level. The model is calibrated on the database for the years 2001-2005 and the so modeled Reference_2003 than is projected to the year 2015 (BAU_2015), this to evaluate the model results without the influence of the great changes in agricultural policy in the last years. Based on the modeled situation for the year 2015 further scenarios are defined that differ in the expansion of energy cropping and nature conservation measures. In the ?biomass scenarios? only the legal nature requirements have to be met while in the corresponding ?conservation scenarios? restrictions that are optimal from a nature conservation point of view, must be considered. The sensitivity analyses for selected parameters proved that the model results have sufficient stability to make reliable statements about synergy effects and conflicts between the expansion of energy crop cultivation and requirements for natural conservation. Altogether it could be shown that with the used model approach interactions be-tween the cultivation of energy crops and nature conservation are represented sufficiently and the objectives of energy and climate policy are compatible.
Nitrogen-rich and lignocellulosic biomass for biogas production : methane yield potentials, process stability and nutrient management
(2023) Morozova, Ievgeniia; Lemmer, Andreas
A sustainable energy supply and bio-based economic processes are of central importance for the future development of many Eastern European countries. Due to the large agricultural potentials of these countries, bioenergy systems can make a significant contribution to sustainable electricity and heat production if they are reasonably integrated into an energy supply structure based on various renewable energy sources. This requires the use of regenerative starting products and the complete utilisation of all by-products of the overall process. With such a cradle-to-cradle approach, biogas technology can be a central component of future energy systems. The focus of this study is on Ukraine. In the future, bioenergy villages can make a decentralised contribution to a sustainable energy supply in this country. This study aims to determine the methane yield potential of various energy crops from Ukraine, investigate the process stability during fermentation in biogas plants and derive concepts for optimized digestate management. Seven different crops with a total of 22 varieties were investigated for their specific biomass yields, methane yields and areal methane yields. The crops were cultivated in Ukraine. The biogas production potential of the collected crop samples was determined using the Hohenheim Biogas Test in Germany. The Ukrainian variety “Osinnii zoretsvit” of miscanthus, “Giganteus” species, from the 8th year of vegetation, harvested at the stem elongation stage, resulted in the highest areal methane yield of 7404.55 ± 199.00 m3*ha-1 and the lowest N requirement per unit methane produced (23.41 ± 7.18 gN*m-3) among all the studied crops. The maize variety "Svitanok MV" (FAO 250) had the highest value of areal methane yield of 6365.67 ± 55.49 m3*ha-1 among the annual crops when harvested at the stage of wax maturity; remarkable was its unusually high specific methane yield of 0.41 ± 0.00 m3*kg-1VS. The Ukrainian sugar sorghum variety "Favoryt", harvested at the beginning of flowering, had an areal methane yield of 5968.90 ± 82.70 m3*ha-1, making it an attractive alternative energy crop for Ukraine. In the second part of the work, experimental investigations were carried out to test how N-rich substrates influence the stability and efficiency of the biogas process. For this purpose, different variants with various N-increase rates of the input materials at two initial concentrations were evaluated in the laboratory. The continuous trials were conducted over a period of 33 weeks. The modelling procedure was applied to evaluate the effects of TAN (total ammonia nitrogen) and FAN (free ammonia nitrogen) on the degree of methane production inhibition for all scenarios studied. It was concluded that the higher the N-increase rate in the feeding regime, the more methane production is inhibited. The maximum nitrogen concentration in the digestate achieved during stable fermentation processes in this study was 11.5 g*kg-1FM, which corresponded to the values of TAN and FAN of 9.07 g*kg-1FM and 0.85 g*kg-1FM, respectively. These values are much higher than those reported up to now in the literature. At the same time, process efficiency decreased with increasing nitrogen concentrations. As a final step, the technology for nutrients recovery from digestate was developed and tested in this work. First, the digestate separation with a screw press separator was carried out as a "benchmark" at the research biogas plant "Unterer Lindenhof" on a technical scale. Subsequently, a methodology for digestate separation at laboratory scale was developed based on a tincture press, which corresponds to the technology used in practice. The effect of pretreatment of digestate with various biocoal-based additives was studied. In this study, six variants of biocoals synthesized at either 350 °C or 600 °C and partially impregnated with Mg or Ca before pyrolysis were produced. Different reaction times and conditions between the biocoals and the digestate were tested. The results on nutrient removal showed that the biocoals impregnated with Mg prior to pyrolysis had a positive effect on nutrient removal efficiency. The Mg-impregnated biocoal synthesised at 600 °C showed removal efficiencies for NH4+, P and K of 56.04%, 66.66% and 51.77%, respectively. These values were much higher than those for the control variant and much higher than the values found up to now in the literature. By using the nutrient-rich solid fraction of the digestate as fertiliser to cultivate bioenergy crops for further use in biogas production, the production cycle is closed, and the cradle-to-cradle approach is achieved.
Ökonomische Bewertung regionaler Wettbewerbspotentiale verschiedener landwirtschaftlicher Biomassen im Rahmen der Bioökonomie unter besonderer Berücksichtigung Baden-Württembergs
(2020) Petig, Eckart; Bahrs, Enno
The finite nature of fossil resources and climate change pose major challenges to the global society and require a comprehensive transformation of the current economic system. One important aspect of this transformation, also known as bioeconomy, is the transition from a fossil-based to a bio-based supply of raw materials. In this context, agricultural production represents an important supplier of raw materials, which in Germany is already characterized by a strong competition for the scarce land. The scarce land is a major challenge of the expansion of the use of agricultural biomass for the bioeconomy. Accordingly, the derivation of the potential of agricultural biomass for bioeconomy requires consideration of the tradeoffs between various utilization paths. In this context, economic models can be valuable methods, which on one hand are able to depict the trade-offs of different value chains and can, on the other hand, incorporate the uncertainty by developing suitable scenarios. The aim of this thesis is the evaluation of the potential of different agricultural biomasses for the bioeconomy and to analyze the associated effects on agricultural production structures in Baden-Wuerttemberg. In chapter 2 the potential of grassland as a biogas substrate is evaluated, which might be important for the bioeconomy in the future. Due to the more complex harvesting process and partly unfavorable production conditions, grassland has higher production costs compared to arable biogas substrates. The consideration of iLUC Factors with high prices for GHG emissions could improve the competitiveness of grassland to such an extent that it is competitive with the production of biogas substrates on arable land. However, silage maize is often the more favorable biogas substrate in many respects, as chapter 3 shows by means of a site modeling for biogas plants in Baden-Wuerttemberg. In chapter 4 and 5 the potential of straw for energetic and material use is analyzed. These investigations are based on the combination of EFEM with the techno-economic location optimization model BIOLOCATE. The results clearly show the interaction between the economies of scale and the rising raw material supply costs. On the one hand, the average investment costs decrease with increasing plant size, but on the other hand the raw material costs increase, because the transport distances increase and an increasing demand for biomass results also in higher market prices. Additionally, the results show that straw can make a fundamental contribution to the bioeconomy by providing regional bioenergy and as feedstock for material value chains. However, even the use of by-products can have effects on cultivation structures and thus, reduce the production of agricultural biogas substrates, among other things. In Chapter 6 the effects of macroeconomic expansion paths of the bioeconomy on agricultural production structures in Baden-Wuerttemberg are investigated. For this purpose, the results of an iterative model coupling between the agricultural sector model ESIM and the energy sector model TIMES-PanEU of four bioeconomic scenarios are scaled down from national level to regional and farm level using EFEM. The results show different impacts on farm types and thus illustrate the advantages of a differentiated analysis of the expansion of the bioeconomy. Therefore, farms with mainly extensive production methods such as suckler cow husbandry do not profit from the expansion of the bioeconomy due to unfavorable production conditions, while especially large arable farms in fertile regions would benefit disproportional more than the average. Basically, the results reveal limits to the mobilization of additional biomass potential. The reason for this is the already high cultivation intensity of agricultural production in Germany, in which the expansion of one production restricts production of another due to competition for the limited agricultural land. For grassland, the results show that the decline in grassland-based cattle farming and unfavorable economic conditions can lead to a significant increase of unused grassland. Grassland thus presents itself as a promising resource for biomass production for the bioeconomy, as it can provide important ecosystem services (e.g. biodiversity) in addition to the provision of raw materials. However, a political framework has to be established that promotes ecological services accordingly. Finally, in chapter 7 additional research needs are identified, which include further development of the methodological approach. These comprise an extension of the analysis by macroeconomic models to integrate interactions with the material use in a more detailed way. Furthermore, an integration of ecological parameters is necessary for a holistic analysis in the context of bioeconomy.
Physiological and growth responses of Jatropha curca L. to water, nitrogen and salt stresses
(2012) Rajaona, Arisoa Mampionona; Asch, Folkard
This thesis provides necessary and complementary information for an improved understanding of jatropha growth to guide further research to evaluate the response of jatropha to abiotic stressors and for designing plantations adapted to the plants? requirements. Given the fact that jatropha is claimed to grow on marginal lands, we studied effects of water supply, salt stress, nitrogen and air humidity as major abiotic stressors on gas exchange parameters and biomass production followed by management options for pruning the trees to positively influence biomass productivity and to contribute to optimize resource use. The effects of water availability (rainfed versus irrigated) on growth and gas exchange parameters were investigated for 4-year old jatropha grown in a semi-arid environment at a plantation site in Madagascar in 2010. The results confirmed that 1250 mm water in addition to a 500 mm rainfall did not affect biomass production and instantaneous gas exchange. Nevertheless, leaf light responses of irrigated plants were higher than that of rainfed plants. The study showed to what extent salt stress affected water use, canopy water vapour conductance, leaf growth and Na and K concentrations of leaves of 3-year old and young jatropha plants. 3-year old plants were exposed to seven salt levels (0-300 mmol NaCl L-1) during 20 days and young plants to five salt levels (0-200 mmol NaCl L-1) during 6 days. In both experiments, plants responded rapidly to salt stress by reducing water loss. The threshold value of responses was between 0 and 5 dS m-1. Leaf area increment of young jatropha had a threshold value of 5 dS m-1 implying that jatropha is sensitive to external salt application in terms of canopy development, conductance and CO2 assimilation rate. Transpiration of plants in both experiments was reduced to 55% at EC values between 11 and 12 dS m-1 as compared to non-stressed plants. These findings indicate that jatropha responds sensitive to salt stress in terms of leaf elongation rate and consequently canopy development, and to immediate physiological responses. Leaf gas exchange characteristics of jatropha as affected by nitrogen supply and leaf age were intensively studied, as carbon assimilation is one of the central processes of plant growth and consequently a key process embedded in modelling approaches of plant productivity. This study showed that N supply effects on leaf gas exchange of jatropha leaves were small with only the treatment without nitrogen resulting in lower rates of CO2 assimilation rate and light saturated CO2 assimilation rate, nevertheless, effects of N supply on biomass formation were pronounced. Instantaneous rates of leaf gas exchange of different leaves subject to variable air humidity (atmospheric vapour pressure deficit (VPD)) were investigated. This study showed that CO2 assimilation rate (A) and stomatal conductance (gs) were correlated in a hyperbolic fashion, and that gs declined with increasing VPD. Maximal stomatal conductance of jatropha was in the range of 382 mmol m-2 s-1 and gs is predicted to be close to zero at 6 kPa. Effects of VPD, via stomatal conductance, by preventing high transpiration rates, have been demonstrated to be decisive on water use efficiency. Our findings are in this regard relevant for the estimation of water use efficiency of jatropha. The outcome further indicates favourable conditions at which stomatal opening is high and thereby allowing for biomass formation. This information should be considered in approaches which aim at quantifying leaf activity of field-grown bushes which are characterized by spatially highly diverse conditions in terms of microclimatic parameters. Microclimatic parameters can be modified by the tree structure. The reported field experiment on 4-year old jatropha indicated that the biomass production and canopy size depended mainly on primary branch length. A comparison of plants of different pruning types with regard to trunk height (43 versus 29 cm) and total length of primary branches (171 versus 310 cm), suggest that higher biomass production and greater leaf area projection was realized by trees with short trunks and long primary branches. Growth of twigs and leaves was positively correlated with total length of branches. Relative dry mass allocation to branches, twigs and leaves, length of twigs per cm of branches and specific leaf area were not affected by pruning and water supply. Trees with shorter branches had a higher leaf area density. As opposed to an allometric relationship between the average diameter of primary branches and total above ground biomass, our data suggest that these traits were not constantly correlated. Our data indicate that the length of newly formed twigs, where the leaves are attached to, can be related to the total length of already established branches. Leaf area density and relative dry mass allocation to leaves were not affected by the two pruning techniques, indicating that pruning differences in leaf area size were proportionally converted to corresponding pruning differences in the canopy volume exploited by plants. The results reported in this study are relevant for understanding jatropha growth. It helps farmers first for a better plantation management and researchers as well as contribution to future modelling purpose concerning jatropha growth under variable climatic conditions. Additionally, it should complement information for a better set of priorities in research, contribute indirectly to breeding programs and adjust agricultural policies in terms of encountering global change.
Sustainable bioenergy cropping concepts : optimizing biomass provision for different conversion routes
(2014) Mast, Benjamin; Claupein, Wilhelm
Today energy from biomass already contributes to a considerable share to the global energy consumption. In particular, certain modern bioenergy streams like biogas, biofuels for transportation etc., are of increasing relevance. However, several of the beneficial aspects, which were initially attributed to the utilization of today’s bioenergy, had to be relativized and the controversies regarding environmental and socio-economic drawbacks have, in the meanwhile, been on the rise. Alongside a shift to advanced conversion technologies, the improvement of bioenergy cropping systems towards a sustainable biomass provision is a key element of future bioenergy production. Against this background, the present thesis assessed various aspects in terms of biomass production, biomass provision and biomass conversion mainly addressing the two bioenergy streams – 2nd generation biofuels and biogas. For biogas, the thesis addresses aspects regarding the development of alternative cropping systems, the evaluation of novel crops for biogas purpose, and the assessment of regional biogas potentials using a crop growth model. The second focus of the thesis was set on biofuels while special attention was given to the production of microbial biodiesel, and the characterization and evaluation of potential feedstocks for this purpose.