hohPublica :: Browsing by Subject "Effizienz"

Browsing by Subject "Effizienz"

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A full-scale study on efficiency and emissions of an agricultural biogas plant
(2013) Nägele, Hans-Joachim; Jungbluth, Thomas
In this study we focused on process engineering for the conversion of biomass, and utilization of the gas obtained by fermentation. Several topics regarding efficiency and emissions have been addressed by conducting intensive and long-term measurements. In detail, our objectives were (1) to conduct long-term measurements of the electric energy consumption of the biogas plant and its individual components and examination of energy-saving potentials; (2) to develop a method to measure mixing quality in the digester and to examine the mixing quality by measuring nutrient distribution in the digester with different agitator setups; (3) measure the influence of maintenance strategies on efficiency and emissions at long-term operation in practical application; (4) examine the efficiency of an external biological desulfurization plant under practical conditions to enhance biogas fuel quality. The results of electric energy measurement over a period of two years showed that a percentage of 8.5% (in 2010) and 8.7% (in 2011) of the produced electric energy was required to operate the biogas plant. The consumer unit agitators with 4.3% (in 2010) and 4.0% (in 2011) and the CHP unit with 2.5% (in 2010 and 2011) accounted for the highest electrical power demand, in relation to the electric energy produced by the CHP unit. Calculations show that the agitators consumed 51% (in 2010) and 46% (in 2011) of the total electric energy demand. The results stress the need for further research in the fields of substrate homogenization in biogas plants in order to reduce the demand for electric energy. Based on the results of electric energy consumption, follow-up studies have been conducted on nutrient distribution, which depends on agitator type and agitator regime. The investigation showed that significant differences in local concentrations of organic acids, which are not correlated to DM content, are found in dependence on agitator type and agitation regime. Measurements on electric energy consumption of the different agitator types verified that, depending on the agitator type, the saving potential rises up to 70%. The results for emissions and efficiency of the CHP unit confirm the fact that after readjustment of the air-fuel ratio (Lambda value), the emission values for NOx decline while CO increases. However, the emission-optimized operation mode leads to lower engine efficiency. The permanent measurements proved their legitimacy showing various emission deviations from the limiting values prior and post maintenance. In addition, the results show that by monitoring the lubricating oil quality, the oil change intervals can be maximized, while ensuring that engine performance is not endangered. This allows the operator to reduce maintenance expenditures while minimizing wear. To increase engine efficiency, the reduction of the lambda value combined with exhaust gas scrubbing and exhaust gas power generation is a promising approach. However, that would presuppose a permanent and almost total removal of H2S from the biogas. The fourth part of the study examined the technical and economic feasibility of a Fixed Bed Trickling Bioreactor (FBTB) for external biological desulfurization of biogas. In contrast to well-established biological methods to oxidize H2S, the FBTB allows removal of these from the biogas process, thus ensuring a constant low H2S concentration in the biogas. The FBTB showed H2S removal efficiencies (RE) of 98% at temperatures between 30-40°C. A major decline in RE in a range of 21-45% was observed when temperature in the FBTB dropped to a range of 5-25°C. The results revealed that different pH values of the percolation fluid and air ratios have little effect on RE. The practical use of the investigated FBTB system is an interesting technological alternative as disadvantages of internal biological desulfurization methods are being avoided. Due to high expenditures for operation resources and maintenance for FBTB operation during the research, a technical optimization is necessary to ensure economical operation. The results presented in this thesis show that the scientific instrument ?research biogas plant? is the ideal supplement to methods such as laboratory scale research and measuring programs. Research at full scale offers an entirely new opportunity to determine the interaction of process technique and process biology and to conduct long-term studies of gas utilization. Compared to measuring programs at commercial biogas plants, the research biogas plant has the advantage of being significantly better equipped with measurement technologies and that economic success is not the overall goal.
Agricultural education in Honduras : return on investment, quality, and efficiency
(2020) Flores Rios, Maria Delfina; Knierim, Andrea
The Agri-food sector, like any other economic sector, requires competent workers and entrepreneurs able to maximize productivity and cope with the various challenges the sector is facing. Agricultural education prepares these actors to acquire knowledge, identify options that optimize their productivity, and adapt to changing environments. However, the importance of agricultural education is declining in education policies, and nowadays, it is no longer an attractive field of study for the youth. There is a need to re-invent agricultural careers to the new demands of the agri-food and labor market sectors. As there is a limited number of studies available that analyze agricultural education in Latin-American and other developing countries, this research provides new insights by examining the determinants for return to investment, quality, and efficiency of agricultural education, taking Honduras as a case study. The present dissertation encompasses three interrelated studies. The first study addresses the research question on how the educational attainment on agricultural education, years of experience, age, sex, geographical region of residence, and work sector, affect the graduates earnings. This study computes the return to agricultural education by educational level, using several econometric techniques, such as the instrumental variables, Heckman’s two-step procedure, and the multinomial logit to tackle endogeneity of education, sample selection bias, and selection bias for choosing this field of study, respectively. The results show that regardless of the economic activity in which the individuals work, graduates from agricultural educational programs receive positive returns on their investment in education. High school graduates from these programs, have higher earnings within the economic activity of agriculture than non-graduates. At the university level, the graduates competencies are better paid in economic activities outside agriculture than inside, for example, in fields of manufacturing, public administration, and education. The second study addresses the question of what competencies employers require from graduates of agricultural education programs. Interviews and workshops were conducted, addressing employers from agricultural value chains, purposely selected, and using maximum variation sampling. The results show that graduates perform at an intermediate level in technical competencies. Of the 20 competencies identified, graduates perform poorly in at least six areas of competence, which requires immediate action. Although the analysis of academic curricula shows that the competencies included are relevant for employers to cope with the challenges faced by the agri-food sector, there is room for improvement. Finally, the third study addressed the question about the level of efficiency of the public institutions delivering agricultural educational programs, and the factors influencing it. This study computes the efficiency using the non-parametric approach data envelopment analysis (DEA). The model used is output-oriented, variable return to scale, and two-stage where controllable and non-controllable inputs are included in the first and second stages, respectively. This study follows a double bootstrapping procedure to avoid the caveats of the conventional DEA analysis. The evidence showed that none of the agriculture education centers in the sample is considered a full efficient entity. However, there is a potential to improve the usage of the current resources. It is possible by expanding the outcomes in a range of 1% to 50% without changing the existing resources. In summary, the findings of this dissertation provide compelling evidence that each additional level of agricultural education in Honduras is a worthwhile investment, and that graduates from both education levels, secondary and tertiary levels, are necessary to support Honduras economy. Nevertheless, improvements should be made in terms of the quality and the resources used in the provision of agricultural education. Based on the research findings, it is recommended to revise the academic curricula, with the aim of better matching education and labor market requirements. Secondly, a closer analysis of the implementation of the educational processes is necessary in order to enhance the competencies requested and identify better management of the resources available. Finally, setting formal collaboration mechanisms between the education centers, authorities, and the private sector could strongly improve agricultural education systems’ contribution to the performance of the sector. To further refine this research, it would be beneficial to increase the sample sizes to expand further the techniques used.
Development and evaluation of methods for assessing the efficiency of biogas plants
(2022) Hülsemann, Benedikt Werner; Müller, Joachim
Biogas is a renewable energy source with main advantages compared to other renewable energy sources. The advantages include the use of organic waste as a substrate, local power and heat production, rural job creation, the possibility of a flexible gas production and a product which can easily stored and transported in a gas grid or on the roof of a digester. However, the development of the biogas sector is highly dependent on the costs of producing gas, electricity and heat. The production costs are higher than the costs for other energy sources. Growth of the biogas sector is therefore only possible if there is political promotion for biogas as there was in Germany through the EEG. Nowadays, due to the reduction of bonus payments in the EEG 2017 and EEG 2021 in Germany as well as the lack of policy promotion in several other countries, lower production costs based on a higher efficiency are essential to help the biogas sector grow further. In order to achieve higher efficiency and to tap the full potential of biogas, the efficiency has to be determined, which is done in this thesis. The input methane potential is determined using 6 different methods. These methods are compared on the basis of an investigation of 33 German agricultural BPs as well as one German and one US BP using food waste as feedstock. The four methods based on the batch test show a high sensitivity. Unfortunately, they also show efficiencies greater than 100% for most BPs, clearly indicating an underestimation of the degradable potential. Only for the US BP can an efficiency less than 70% be reported. This result is probably based on the lack of heating system corresponding to the lack of promotion of heat recovery in the US. The CE according to the BMP method also reveals an average efficiency of 95% for the German BPs. The values of the two gross calorific value-based methods show efficiencies below 100%, but with low sensitivity. The results of these methods can be used to determine the further potential of a bioeconomic process and to compare the biogas process with other industrial processes. There are several impact factors that affect the accuracy of the efficiency measurements. The installed meters are not frequently calibrated at most BPs. Also, some meters are almost completely missing, as only few BPs in Germany have a gas flow meter. Thus, assumptions and calculations are required to determine the efficiency. In the developed method, the gas flow must be calculated from the amount of the power production, the calorific value, the gas quality, the CHP unit efficiency and the conversion loss at the transformer. The last two values must be assumed, even if the database is small. Another important parameter is the feeding mass. It is measured by the German BPs, but in some cases, the data quality is low. For example, different crops are mixed in the silos and measurement of each substrate is not possible. This leads to measurement errors shown by the organic dry matter mass balance, which has a residual value of up to 24%, while only 11% can be occur based on water incorporation into the ODM. Another factor having an impact is the sampling. The results of a monthly sampling throughout the year show a fluctuation in the DM/ODM values. To investigate the accuracy of the methods used to determine the SMP of the substrate, the biochemical methane potential test is examined in detail. The BMP consists of the used inoculum, the substrate, the digestion system and the calculation. The impact of the used inoculum and the digestion system is investigated by using different inocula in one digestion system as well as by using the same inoculum in multiple digestion systems. The inocula used in this thesis are well-known and have been used in interlaboratory tests for several years. Thus, outliners were excluded. A CV of 4.8% can be reported between the different inocula, which is lower than reported in most other publications before. The use of different digestion systems shows a higher CV of up to 12.8%. For the inoculum and the digestion system, the deviation varies strongly and no clear correlation can be identified. Therefore, a correction of this effect is not possible. The biological yield efficiency of 21 of the investigated BPs is in the range of 100 ± 12.8%. This reveals the need of stricter rules for the digestion system. All digestion systems used in this thesis are described in the German guideline VDI 4630. The calculations were also done according to the German guideline VDI 4630. An influence can be neglected. However, if the results of a measurement with already dried gas are compared with the results of a calculation according to VDI 4630, which is based on the measurement with wet gas, a discrepancy can be found. Although, the CV using only one digestion system and one inoculum is only 1-7%. A comparison of the efficiency of different BPs by using the same inoculum and digestion system is hence recommended.
Efficiency of selected fiscal policy instruments
(2017) Dekker, Vincent; Dwenger, Nadja
The thesis at hand intends to contribute to the understanding of behavioural responses to taxation by dedicating each chapter to the analysis of a different fiscal policy instrument. Chapter 2 focusses on the individual tax system in the Netherlands that exhibits tax brackets, as opposed to a smooth progressive tax system. The aim is to uncover the extent of behavioural responses to the kinks in the budget set that are created by the non-linear increases in the marginal tax rates at the tax brackets cut-off points. From the analysis it becomes evident that individuals react to jumps in the marginal tax rate. First, an extension to the classical bunching approach introduced by Saez (2010) and extended by Chetty et al. (2011) is provided. Because individuals face optimisation frictions, perfect bunching at the kink as predicted by theory is not observable. Rather, a window around the kink, known as the bunching window, is used in the analysis. Where prior research had relied on visual inspection to determine the size of the bunching window, a data-driven procedure is proposed instead, which is shown to be robust to variations in various parameters and takes away the researchers discretion in that matter. Thus, a methodological contribution to a comparably young, but growing field of research is made. Chapter 3 discusses the implications of the introduction of transfer pricing regulations (TPR) on intermediate goods trade. The chapter thus analyses an anti-avoidance measure implemented by many governments in recent years and evaluates the consequences for allocative and distributional efficiency. The empirical literature has shown that multinational enterprises (MNEs) utilise transfer prices to shift profits into (out of) low-tax (high-tax) jurisdictions. Evidence was given in prior literature that MNEs react sensitively to the introduction of TPR in reducing (increasing) their prices when they were overvalued (undervalued) before the implementation of regulations. Surprisingly, a reaction in quantities, i.e. shifts in production and trade flows, had not been analysed in the literature before. The results indicate a substantial quantity reaction and also a pricing reaction, which is shown to be in line with the literature. This suggests that before the introduction of TPR, firms shift more exports to low tax countries and less exports to high tax countries for tax optimising purposes. Following the introduction of TPR, especially the reduction in quantities traded with low tax countries is identified. Chapter 4 deals with a recently developed tax incentive for research and development (R&D), namely the intellectual property box (IP-Box). Said to foster innovation by the implementing governments, critics accuse the IP-Box regimes of providing yet another profit shifting opportunity for multinational enterprises (MNEs). The study assesses the implications that the introduction of IP-Box regimes has on innovation and shifting behaviour, in order to judge on the efficiency and effectiveness of such a policy instrument. Whilst most R&D incentives are ex ante tax incentives, i.e. incentives that act during the innovation process and before the innovative product was developed, IP-Boxes are an ex post tax incentive, thus only benefiting successful R&D. The analysis attempts to explore whether IP-Boxes are a local innovation enhancing device, as propagated by the countries implementing IP-Boxes, or merely facilitate profit shifting for MNEs by offering a substantially lower tax rate on income from intellectual property. The results clearly show that the shifting channel dominates the home innovation channel. Some evidence is found that home developed patents were crowded out by foreign developed and subsequently shifted patents. The total number of patents does not seem to react to the introduction of IP-Boxes, thus even questioning the global innovation enhancing effect of IP-Boxes. Given the nature of the country level data, it is not possible to investigate the different designs of IP-Boxes more thoroughly, although the implementation of a development condition should be part of every IP-Box regime. This ensures that, at least from a global or even European perspective, innovation must take place somewhere.
Ethical banking and finance : a theoretical and empirical framework for the cross-country and inter-bank analysis of efficiency, productivity, and financial performance
(2012) Abu-Alkheil, Ahmad; Burghof, Hans-Peter
Islamic banking is a growing worldwide phenomenon involving a variety of institutions and instruments. Previously, Islamic banks? transactions made up a small part of the total banking industry. Recently, Islamic banks have significantly expanded their network, and have been able to mobilize a large amount of funds and upgrade many economic ventures. Given the unique behavior of Islamic banks and their involvement in both social and economic activities, there has always been a question about their long run financial sustainability, particularly in adverse market conditions. Thus, a reliable and unbiased estimation of Islamic banks?efficiency and productivity performance is essential for the evaluation of Islamic banking operations within and outside its traditional borders of Muslim economies. Due to the short history of Islamic banking in Europe, and consequently the lack of sufficient data, empirical researches on the financial performance of Islamic banking have concentrated primarily in Muslim-majority countries and focused on the theoretical issues and descriptive statistics rather than rigorous statistical and econometric estimation. The main purpose of our analysis is to bridge this gap in the global and cross-country literature and to contribute to the ongoing debate regarding the performance of Islamic banking. Therefore, the orientation of this thesis is chiefly quantitative in nature. The aim of this thesis is primarily to shed some light on the emergence and the continual global growth of Islamic banking all over the world. It also tries to assess, for the first time, the relative performance of Islamic commercial and investment banks operating in Europe against counterparties-conventional banks in Europe and also against Islamic banks from Muslim-majority countries. Our methodology in this academic work clearly differs from the literature researches. This thesis is, basically, divided into two main parts. In first part, we specifically discuss the basic features and principles of the Islamic banking and finance. We then reviewed several in-depth market analysis results concerning Islamic banking and finance that were performed by well-known specialized financial institutions. In the second part, we primarily utilize different empirical approaches to examine the performance of our sample banks which shows a great variety, ranging from large active banks to new and small banks. More specifically, we use the Data Envelopment Analysis (DEA) method to calculate the commercial banks? efficiency scores and investment banks (cost)-X-efficiency levels; the DEA-based Malmq- uist Productivity Index (MPI) to estimate the banks productivity indices; the common financial ratios to measure the banks financial performance; the T-Test to determine the differences of investment bank's performance pre- and post- the financial crisis that hit the world?s economy in 2007; the Ordinary Least Squares (OLS)-regression to determine the impact of internal and external factors on bank's efficiency and also to check the robustness of the overall results obtained from DEA scores; Spearman's rho correlation to investigate the association of the DEA-efficiency scores with the traditional accounting ratios; and eventually the efficiency?profitability matrix in order to determine the characterization of the banks' performance and the factors that influence efficiency. Our analysis is carried out, primarily, over the period from 2005 to 2008. This indeed helps to account for the impact of the recent financial crisis on the efficiency and productivity performance of the selected banks. The preliminary review of the market surveys-based analysis shows that the Islamic finance and banking is one of the fastest growing sectors in the financial world. Islamic financial products and services are increasingly being regarded as a viable investment opportunity, making them very attractive for Muslims and non-Muslims alike. Leading Islamic banks from Muslim countries are expanding their network. Several European banks have directly involved in providing Islamic financial products in order to satisfy the special needs for Muslim customers and the non-Muslims who seek ethical financial and investment solutions. Eventually, European governments have also started to amend their legal, tax, and regulatory systems to allow the establishment of Islamic banks. Most importantly, from an empirical point of view, our presented results suggest that the Islamic commercial banks in Europe are found to be relatively technically inefficient. They have also, on average, poor financial performance and under-performing practices. Moreover, Islamic banks in Europe actually suffer from significant productivity losses over the sample years driven, to a large extent, by the regress in banks? technology innovations. By and large, the bank?s inefficiency stems from both the sub-optimal size of operations and the lack of management knowledge and skills. Findings suggest that the optimal size for Islamic banks to achieve better levels of performance is neither large nor small rather medium. Therefore, increasing banks size through mergers and acquisition will substantially enhance their technical efficiency and productivity progress. The period prior to the current financial crisis was marked by the most stable economic environment for generations. Our results illustrate that Islamic banks lag relatively, before the emergence of the crisis, behind their conventional peers in terms of estimated efficiency scores and productivity changes. Strikingly, conventional banks gradually lose their superiority over Islamic banks in subsequent years, but remain, on average, a head of Islamic banks. Islamic banks are, indeed, less vulnerable to the effects of the crisis as compared with counterparties-conventional banks. They exhibit only slight inefficiency and productivity regress during this severe crisis and therefore, produce a consistent and remarkable positive trend in technical efficiency, productivity performance, and financial profitability. This might be because of the beliefs in the power of petro-dollars in the Gulf region, the fact that the Islamic banks are relatively small and young at present, and could also be due to the religious financial constraints. Such factors might have played an important role in preventing Islamic banks from being severely affected by the crisis. Overall, results suggest that the small and new Islamic banks in Europe can be as efficient and productive as large and old Islamic and conventional banks. They also have long run sustainability, substantial room for improvements, and a great potential in the banking industry to sustain their competitive edge not only in Muslim countries but also in the European financial system. The estimated findings pertaining to the performance of Islamic investment banks in Europe suggest that these banks experience low (cost)-x-efficiency and poor allocative-efficiency compared with counterparties-conventional banks. Bank?s inefficiency is caused largely by the under-utilization of inputs, the bank's diseconomies of scale, and also appears to be due to the regulations not controlled by management due to fluctuations and instability in factor prices. Islamic investment banks additionally show a clear paradox between their high calculated efficiency scores and low achieved profitability ratios. They are also less risky, more solvent, and operate with lower use of debt. Nevertheless, Islamic investment banks suffer a gradual deterioration in liquidity position. The banks' supply of Murabaha (cost-plus loans) financing appears to be most dominant and has increased significantly in importance. Overall, findings seem to reveal that the banks that are technically more efficient are larger in size (total assets), financially more profitable, have greater loans intensity, acquire lower levels of debt, invests more in appropriate human skills, have a lower market share (total deposits), and operate in countries with higher GDP-per capita. Such results reflect the strong and high association between the DEA-efficiency measures and the standard accounting measures, suggesting that the DEA approach can be adopted separately or concurrently along with financial ratios to make comparisons of Islamic banks performance more robust.
Fertilizer quality and its impacts on technical efficiency and use intensity in the North China Plain
(2014) Khor, Ling Yee; Zeller, Manfred
There has been a significant increase in agricultural output in the past 50 years. A major factor of this growth is the rise in input use such as fertilizer, especially during the beginning of this period. However, the trend is not uniform throughout the world. Even though there are still regions where fertilizer can contribute greatly to the increase in yield, this input is so overused in some other places that its marginal productivity is no longer significant. In this case, not only is it a waste of valuable resources, it also leads to environmental degradation and pollution that is detrimental to human health. To make matters worse, the quality of the agricultural input itself has been of increasing concern lately. It includes problems such as normal seed being sold as hybrid seed, pesticide that is mixed with less effective chemicals, or fertilizer which contains less nutrient than that labeled on the package. We focus our research on the North China Plain, a region with both fertilizer overuse and fertilizer quality problems. The issue of low fertilizer quality is however not confined to this region only, as recent news reports have indicated that substandard or fake agricultural input is a problem in other countries as well, for example Bangladesh, Cambodia, Nigeria, Tanzania, and Vietnam. In addition, although the analysis presented in this dissertation concentrates on fertilizer, some of the methodology can also be extended to examine the impact of other agricultural inputs with questionable quality, such as seed and pesticide. The main theme of our study is split into three subtopics: efficiency, wealth effect, and use intensity, with each of them focusing on a different aspect of the impact from low quality fertilizer. The main contribution of this dissertation is that despite the widespread problem of fertilizer quality, we believe we are the first to examine its impact both theoretically and empirically on efficiency and use intensity. The theoretical contribution includes deriving the bias that exists if one were to ignore the quality aspect in the estimation of production functions and technical efficiency, especially if the research area is located at one of the places with fertilizer quality problems, such as China and the other affected countries. We also provide a theoretical framework that reconciles the different findings in the literature on the direction of wealth effect on fertilizer use. It offers a consistent explanation on why the wealth effect can be different when we are looking at regions or farmers of different wealth levels. Empirically, the dissertation quantifies the magnitude of estimation bias in input elasticity and technical efficiency in our research region of North China Plain. It also supports our theoretical derivation and shows that the direction of wealth effect is not fixed across farmers of different wealth levels. Finally, the integration of fertilizer testing into a household survey allows us to look closer at the link between perceived and true fertilizer quality, as well as how they affect the fertilizer use intensity of the farmers. The worsening fertilizer quality issue in the North China Plain is of great concern because - as this dissertation research shows - it leads to an increase in fertilizer use, which is already excessive in the area. This is not only a waste of valuable resources reducing economic efficiency but also causes environmental and health problems, e.g. through pollution of ground water. The currently implemented policy of subsidizing the fertilizer manufacturers is a double whammy in this regard because by keeping the price of the product low, it encourages the usage of an input that is already overused. It also makes the quality control of the fertilizer in the market more difficult, with the presence of so many small scale producers that are inefficient. In view of these deficiencies, it would be better to shift the policy focus from price reduction to quality improvement. A suggestion is to facilitate the award of quality labels to satisfactory products with regular third-party testing of the fertilizer to ensure that its quality does not deteriorate after receiving the label. The honest producers in the industry could also help set up a sector-wide monitoring body to prevent their image from being tarnished by the less responsible manufacturers. An additional recommendation is to increase the resources and staff available to extension service in order to increase the information flow between policymakers and farmers.
Potential impacts of iron biofortification in India
(2006) Bhutta, Zulfiqar A.; Stein, Alexander J.; Qaim, Matin; Meenakshi, J. V.; Nestel, Penelope; Sachdev, H. P. S.
Iron deficiency is a widespread nutritional problem in developing countries, causing impaired physical activity and cognitive development, as well as maternal mortality. Although food fortification and supplementation programmes have been effective in some countries, their overall success remains limited. Biofortification, that is, breeding crops for higher micronutrient content, is a relatively new approach. We propose a methodology for ex-ante impact assessment of iron biofortification, which builds on disability-adjusted life years (DALYs) and a large household data set. Our analysis of iron-rich rice and wheat in India indicates sizeable potential health benefits. The cost-effectiveness of iron biofortification compares favourably with other interventions.
Sorghum breeding strategies for phosphorus-limited environments in Western Africa : from field to genome level
(2014) Leiser, Willmar Lukas; Haussmann, Bettina
A growing world population juxtaposed with dwindling phosphorus (P) resources present new challenges to current and future global agricultural production. The burden of depleting phosphorus resources is particularly felt in sub-Saharan Africa (SSA). The expected doubling of its population by 2050 and the widespread poor soil fertility will pose an enormous task to future food security in SSA. Plant breeding can be considered as one major factor to improve agricultural production under these harsh low-input conditions. Nevertheless, until recently there have been no thorough breeding efforts to enhance crop production for low-P soil conditions in SSA. Sorghum (Sorghum bicolor L. Moench) is the world’s fifth and Africa’s second most grown cereal crop. Sorghum is a staple crop of SSA and is mostly grown in resource poor regions under low-input cropping conditions, with the largest share in West Africa (WA). Its good adaptation to harsh environmental conditions makes it an important crop for the arid and semi-arid regions, hence a crop vital for food security and increasingly farm income in WA. Breeding sorghum specifically targeting P-limited soils is considered as one of the major challenges for future food production and can serve millions of smallholder farmers in WA. Nevertheless, plant breeders are mostly reluctant to conduct breeding experiments under low-input conditions due to a higher spatial variability of soil properties leading to a lower response to selection. In an unprecedented large scale multi-environment experiment from 2006-2012 in three WA countries, namely Mali, Senegal and Niger, 187 WA sorghum genotypes were evaluated for their performance under P-sufficient and P-deficient conditions. The main goal of this study was to establish a breeding strategy for sorghum targeting P-limited environments. In order to establish such a strategy, the following objectives were defined: (I) to evaluate the impact of spatial models on genotypic selection in low-input field trials, (II) to develop a selection strategy for sorghum targeting P-limited environments, based on quantitative genetic parameters and (III) to identify genomic regions influencing sorghum performance in P-limited environments using modern genomic tools. The major findings of this study can be summarized as follows: Spatial models can increase the precision and efficiency especially of low-input field trials and may lead to different genotype rankings. Hence spatial models and/or adequate field designs are necessary tools for efficient genotype selection under low-input conditions and must be considered in a breeding program targeting P-limited conditions. Sorghum performance is severely impeded by low-P soil conditions and shows large grain yield and plant height reductions and delayed flowering. Nevertheless, WA sorghum is generally well adapted to low-P soil conditions and shows a large exploitable genetic variation for P efficiency. Direct selection under low-P conditions is feasible, necessary and more efficient than indirect selection under high-P conditions and should be pursued in a breeding program targeting P-limited environments. Landrace genotypes are more specifically adapted to low-P conditions and show a higher P acquisition capacity, Durra and Guinea race sorghums show a similar specific low-P adaptation, hence these genotype groups are very promising source germplasm for further breeding efforts. Photoperiod sensitive genotypes show less delay in heading, a higher P acquisition rate and a specific low-P adaptation, hence should be considered for climate and low-P resilience breeding. Selection for low P concentration of grain can be used to enhance internal P use efficiency, therefore decreasing further soil P mining. WA sorghum shows a large genetic diversity, hence providing a valuable source for genetic studies examining the underlying genetics of low-P adaptation. There are many genomic regions involved in sorghum adaptation to low-P soil conditions. Nevertheless, some regions could be identified as major contributors, showing large effects on and strong associations to genotypic performance. Molecular markers in sorghum homologs of the major P efficiency gene PSTOL1 from rice stably enhanced P uptake and crop performance through an increased root growth of sorghum under low-P soil conditions and can be used in marker assisted selection for grain yield production under P-limited conditions. Furthermore, it was observed that grain yield production under P-limited conditions and Al-tolerance are pleiotropically regulated by the same genomic region and most probably the same gene SbMATE. Molecular markers of this region and within the gene SbMATE should be used for marker assisted selection to simultaneously enhance the tolerance to two of the most serious abiotic stresses for sorghum in WA, Al toxicity and P deficiency. WA Guinea race sorghums are an excellent source not only for low-P specific alleles, but also for Al-tolerance and represent therefore an excellent source germplasm for allele mining and marker assisted selection. Genomic selection appears to be a very promising approach to further increase the response to selection. But methods giving more weight to single molecular markers linked to Al-tolerance should be considered. The laid out results show that breeding sorghum specifically targeting P-limited conditions is necessary and feasible using advanced statistical models and modern genetic tools, and should be pursued as a major selection criterion in WA sorghum breeding programs. Nevertheless, only by combining agronomic and socio-economic measures with plant breeding efforts, millions of WA smallholder farmers can be reached and major yield increases can be expected in the near future.
Strategies for selecting high-yielding and broadly adapted maize hybrids for the target environment in Eastern and Southern Africa
(2012) Windhausen, Sandra Vanessa; Melchinger, Albrecht E.
Maize is a major food crop in Africa and primarily grown by small-holder farmers under rain-fed conditions with low fertilizer input. Projections of decreasing precipitation and increasing fertilizer prices accentuate the need to provide farmers with maize varieties tolerant to random abiotic stress, especially drought and N deficiency. Genetic improvement for the target environment in Eastern and Southern Africa can be achieved by: (i) direct selection of grain yield in random abiotic stress environments, (ii) indirect selection for a secondary trait or grain yield in optimal, low-N and/or managed stress environments, or (iii) index selection using information from all test environments. At present, the maize hybrid testing programs of the International Maize and Wheat Improvement Center (CIMMYT) select primarily for grain yield under managed stress and optimal environments and subdivide the target environment according to geographic and climatic differences. It is not known to what extend the current strategy contributes to selection gains. The same holds true for genomic prediction, a strategy that is not yet implemented into the CIMMYT maize breeding program but that may accelerate breeding progress and reduce cycle length by predicting genotype performance based on molecular markers. Regarding the different strategies mentioned for selecting high-yielding and broadly adapted maize hybrids, the breeder needs to decide which of them are most promising to increase genetic gains. Consequently, the objectives of my thesis were to (1) evaluate the potential of leaf and canopy spectral reflectance as novel secondary traits to predict grain yield across different environments, (2) estimate to what extent indirect selection in managed drought and low-N stress environments is predictive of grain yield in random abiotic stress environments, (3) investigate whether subdividing the target environment into climate, altitude, geographic, yield level or country subregions is likely to increase rates of genetic gain, and (4) evaluate the prospects of genomic prediction in the presence of population structure. The measurement of spectral reflectance (495 ? 1853 nm) of both leaves and canopy at anthesis and milk grain stage explained less than 40% of the genetic variation in grain yield after validation. Consequently, selection based on predicted grain yield is only suitable for pre-screening, while final yield evaluation will still be necessary. Nevertheless, the prospect of developing inexpensive and easy to handle devices that can provide, at anthesis, precise estimates of final grain yield warrants further research. Based on a retrospective analysis across 9 years, more than 600 trials and 448 maize hybrids, it was shown that maize hybrids were broadly adapted to climate, altitude, geographic and country subregions in Eastern and Southern Africa. Consequently, I recommend that the maize breeding programs of CIMMYT in the region should be consolidated. Within the consolidated breeding programs, genotypes should be selected for performance in low- and high yielding environments as the genotype-by-yield level interaction variance was high relative to the genetic variance and genetic correlations between low- and high-yielding environments were moderate. Genetic gains were maximized by index selection, considering the yield-level effect as fixed and appropriately weighting information from all trials. To allow better allocation of resources, locations with high occurrence of random abiotic stress need to be identified. Heritability in trials conducted at these locations may be increased by the use of row- and column designs and/or spatial adjustment. Furthermore, resources invested into managed drought trials should be maintained during early breeding stages but shifted to the conduct of low-N trials at later breeding stages. Investments in a larger number of low-N trials may increase selection gain, because performance under low-N and random abiotic stress was highly correlated and genotypes can be easily selected under different levels of soil N. Prospects are promising to accelerate breeding cycles by the use of genomic prediction. Based on two large data sets on the performance of eight breeding populations, it was shown that prediction accuracy resulted primarily from differences in mean performance of these populations. Genomic prediction may be implemented into the CIMMYT maize breeding program to predict the performance of lines from a diversity panel, segregating lines from the same or related crosses, and progenies from closed populations within a recurrent selection program. The breeding scenarios in which genomic prediction is most promising still need to be defined. Generally, the construction of larger training sets with strong relationship to the validation set and a detailed analysis of the population structure within the training and validation sets are required. In conclusion, combining index and genomic selection is the most promising strategy for providing high-yielding and broadly adapted maize genotypes for the target environments in Eastern and Southern Africa.
Untersuchungen zur Verwertbarkeit von Pferdemist im Biogasprozess
(2014) Mönch-Tegeder, Matthias; Jungbluth, Thomas
The increasing use of energy crops as the main feedstock and the resulting occupancy of arable land is the central point of criticism of the population in biogas production. Although waste and residues provide significant energy potentials, the conversion of these materials in the biogas process has not been established to date. Significant barriers are the widely varying composition of these materials and their substrate properties. In general, the residues contain a high percentage of fiber, which rises great challenges for the existing process technology. This work aimed to address these challenges by investigating the suitability and usability of the fiber-rich substrate horse manure for biogas production in continuously operated agricultural biogas plants. The study was divided into three consecutive 1. Investigation of the composition and usability of horse manure with different bedding materials and determination of the specific methane yields also taking into account the aging process degradation of horse manure; 2. Determination of the impact of mechanical pretreatment of the substrate with the cross-flow grinder on the specific methane yield and degradation kinetics of commonly used energy crops and horse manure in laboratory-scale; 3. Studies on the feasibility of horse manure in full-scale biogas processes and the effects of mechanical treatment at the research biogas plant "Unterer Lindenhof”. The use of straw-based horse manure in the biogas process is feasible. However, contaminations with alternative bedding materials due to their low degradability must be avoided. Furthermore, a substantial loss of methane potential could be detected due to the storage and meanwhile aerobic degradation. As a result of the high dry matter content and low levels of essential micro- and macro-nutrients, horse manure should only be utilized in biogas plants with suitable co - substrates. The mechanical treatment of silage and horse manure with the cross-flow grinder resulted in a significant reduction in particle size and increased substrate surface. However, no significant changes in the specific methane yield of the investigated silages were observed. Due to the increase of the substrate surface the degradation rate of the grass silage and whole crop silage accelerates. The mechanical disintegration of horse manure resulted in a significant increase of the specific methane yield and a significant improvement of the degradation kinetics. When considering the energy balance of the disintegration, a positive result could only be obtained for the processing of the fiber-rich substrates. Accordingly a previous disintegration of silage for biogas production is not recommended. The results from the investigation of the usability of untreated and disintegrated horse manure in the full-scale biogas process show that the use of horse manure without previous treatment causes serious procedural problems and results in insufficient degrees of degradation. The mechanical pretreatment guarantees a plant operation without failures during this trial. Additionally a complete substrate utilization can be achieved due to the treatment. The additional energy expenditure for the operation of the cross flow grinder was overcompensated by the higher gas yield. The results of this study show, that with a suitable treatment technology, the use of straw based horse manure and other high fiber structural materials in agricultural biogas plants is possible. A complete conversion of straw based horse manure provides an energy equivalent of up to 156,000 ha of maize. Thus, this study helps to improve the sustainability and profitability of biogas production and the achievement of the energy policy objectives.
Vorbehandlung lignocellulosehaltiger Substrate zur Steigerung des Biogasertrages
(2019) Baumkötter, Daniel; Jungbluth, Thomas
There are various approaches for the optimization in biogas technology. One possibility is the pretreatment of the used substrates in order to achieve higher biogas yields, open up new substrates and increase the overall economic viability of biogas plants. For this pretreatment, mechanical treatment technologies are used, which are very different in construction. Therefore, a systematic investigation of the mechanical pretreatment by means of impact with regard to particle size distribution, biogas yield and power consumption for different substrates was carried out for the first time. The aim of this thesis was thus to optimize and eva¬luate the technology “impact reactor” for pretreatment of lignocellulosic substrates for use in an agricultural biogas plant. Substrates with a model character were selected for the experiments, which allow the results to be transferred to comparable substrates. These were triticale straw, oat whole crop silage, maize straw and horse manure. In addition, the substrate mixture of a biogas plant, in which an impact reactor is also used for pretreatment, with a high proportion of grass silage (53 % grass silage, 40 % maize silage and 7 % cattle and horse manure) was examined. Pretreatment of all substrates showed a reduction in particle size. As expected, finer particle sizes also required more effort and therefore higher power consumption. However, no direct correlation could be established between a finer particle size and an increased methane yield. Therefore, an increase in the processing intensity does not necessarily lead to an increase in microbial degradation. In addition to the use of alternative substrates, the main objective of substrate pretreatment was to increase biogas yields. Mechanical pretreatment of triticale straw made it possible to increase methane yield by up to 16 %, horse manure by up to 14 % and substrate mixture by up to 10 %. In contrast, no additional methane yields were recorded for oat whole crop silage and maize straw. Apparently short chopped silages are already sufficiently broken down by the silage. To avoid possible losses due to aerobic degradation, the pretreated substrates must be fed directly into the fermenter. Therefore, the pretreatment should ideally be integrated into the process engineering of the biogas plant between storage and the feed system. In order to classify the results with the impact reactor, additional treatment experiments were carried out with an extruder on a laboratory scale. In principle, the extruder was also suitable for all substrates examined, but liquid had to be added to substrates with a high dry substance content (straw). The results for increasing methane yields were comparable. Besides the investment costs, power consumption had the greatest influence on the costs of pretreatment. These varied significantly depending on the selected settings at the impact reactor. With the help of the determined optimal settings, power consumption of 12.9 kWhel/tFM for triticale and maize straw, 2.6 kWhel/tFM for oat whole crop silage, 10.8 kWhel/tFM for horse manure and 6.1 kWhel/tFM for the substrate mixture could be determined. After combining the results on power consumption and additional methane yield, the mechanical pretreatment of triticale straw, horse manure and the substrate mixture resulted in a gain after energetic balancing. From an economic point of view, horse manure and maize straw showed their potential as an alternative substrate compared to silage maize. Due to their residual material character and the associated lack of market value, these two substrates are economically interesting. By contrast, the market value of cereal straw makes triticale straw more economical than silage maize. However, the results may vary depending on substrate quality and biogas plant, which is why an individual consideration is required for each project. The impact reactor as a method of mechanical pretreatment is basically suitable for various substrates. The pretreatment process increases the biogas yield and opens up previously unused residues for the biogas process, which also improves economic efficiency.

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