Browsing by Subject "Methan"

Now showing 1 - 12 of 12
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    Auswirkungen der flexiblen Biogasproduktion auf die Effizienz von landwirtschaftlichen Biogasanlagen
    (2020) Kress, Philipp; Jungbluth, Thomas
    In future energy systems based on renewable energies, biogas plants can make a significant contribution to stabilizing the electricity grids. However, this requires demand-flexible and load-driven electricity production, which is only made possible by flexible biogas production with extremely versatile feed management. From the process engineering and process biology point of view, this demand-flexible operation represents a major challenge for the operation of biogas plants. Technically, this demand-flexible biogas production requires a complete utilization of the existing fermenter volume, which in turn requires an optimal mixing of the substrates in the fermenter. Similarly, a continuous high-resolution monitoring of the produced biogas composition is also necessary to detect process disturbances or overloads that begin at an early stage. The objective of this work was to test and optimize new measuring methods for the flow velocity measurement and the mixing quality in the biogas reactor. Furthermore, to achieve a high-resolution gas quality measurement, practical scale tests were conducted. From these results, conclusions about possibilities and limitations of a flexibilisation of the biogas production shall be derived. Stirring is one of the most important processes in biogas production. The power input was intended to generate turbulent flows and thus ensure uniform distribution of nutrients and homogeneous temperatures throughout the reactor and avoid sinking and floating layers. In order to be able to assess and optimize these mixing processes, investigations of flow velocities in the fermenter were carried out using a magnetic-inductive measuring system. Additionally, flow profiles were created as a function of the DM content and the viscosity of the fermentation substrate. At a DM content of 9.45% in the fermenter, the average flow velocity measured was 87.5 cm/s. The DM content and the viscosity of the fermenting substrate were also taken into account. This dropped to 0.96 cm/s with a DM content of 9.95%. For the further description of the mixing quality, spatially dissolved nutrient samples were taken from the entire fermenter to determine the biological parameters. It was proven that the punctual input of the solid biomass via the solid input leads to a locally increased DM content and increased concentrations of organic acids in the vicinity of the input. In contrast to the laboratory tests using the process tomography method, no zone was found in the fermenter at which process disturbances were present. Furthermore, in contrast to laboratory tests, no biologically inactive zones could be detected in the fermenter of the research biogas plant. In further investigations, a photoacoustic sensor with a newly developed measuring system for determining the methane and carbon dioxide concentrations of the biogas was installed, tested and optimized for the first time in a biogas plant in the field. The basic applicability of such a system in biogas plants could be demonstrated. The achieved data density was significantly higher than that of conventional devices with a very high precision of the measured values. Using this innovative measuring technique, a flexible substrate supply and its influence on the product gas quality was subsequently evaluated. Substrates with different degradation behavior and different specific methane yields were fed to the fermenter. The influence of the specific substrate used in biogas production was reflected in the biogas quality. In particular, the relation between the relative change in gas quantity and quality makes it possible to detect process changes at an early stage. The presented studies have created a basis that enables a demand-oriented biogas production: Even with high substrate quantities that are fed to the fermenter, a high mixing quality can be achieved in the fermenter with an appropriate design of the agitators, which also prevents local process overloads. The investigations prove that, despite very low flow rates, there is sufficient nutrient supply for the microorganisms. The newly developed sensors for determining the biogas composition provide measured values with high precision and high temporal resolution, so that possible process disturbances can be detected very early. The investigations contribute to optimizing future demand-oriented electricity production on the basis of demand-flexible feeding in biogas plants. As a result, biogas plants can fulfil an important system service in a renewable energy based grid by decentrally stabilizing the electricity supply.
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    Demand-driven biogas production in anaerobic filters
    (2017) Krümpel, Johannes; Jungbluth, Thomas
    Fluctuating energy sources, namely wind turbines and photovoltaic, will be the mayor contributors to the increase in share of renewable energies. The intermittent energy supply by these sources poses challenges for the power grid and need to be counter balanced. A demand-driven energy supply by weather independent biomass conversion can offer these grid services. Flexible energy production from biogas has been identified as a vital approach to provide the grid with positive and negative balancing power. The two-staged anaerobic digestion may be especially suitable for demand orientated gas production due to the advantages of the anaerobic FIlters to withstand high organic loading rates and shock loading. Two staged anaerobic digestion is characterized by a spatio-temporal separation of acidification and methane production. A liquid rich in soluble products, such as volatile fatty acids, alcohols and sugars is produced in the first stage and and is subsequently converted to biogas in the second stage. The methanation stage as the main gas producing unit in such a system is in the focus of this research.The ability to react to sudden changes in demand might be influenced by substrate composition and controlled hydrolysis towards certain intermediates could improve the reaction times towards increased demand. It is therefore one focus of this research work to examine intrinsic methane production kinetics of common intermediates of anaerobic digestion. Other major questions are how fast the methane production can be adapted to sudden changes in demand and to what extent these adaptions are reproducible. It was therefore of interest to demonstrate the feasibility, reproducibility and the possible extent of demand-driven biogas production in anaerobic filters, with respect to changing substrate composition. Furthermore the evaluation of the process effciency based on carbon fluxes should be examined to unfold effects resulting from changing operational conditions. With a newly developed methodology, introduced in the publication "Kinetics of Biogas Production in Anaerobic Filters" kinetic parameters of methane production for individual volatile fatty acids (VFA) could be determined. The bandwidth of tested intermediates was broadened in the second research paper "Intrinsic Gas Production Kinetics of Selected Intermediates in Anaerobic Filters for Demand Orientated Energy Supply". It has been found that intermediates could be ordered according to their half-lives of methane production. The apparent order, beginning with the fastest was acetic acid >ethanol >butyric acid >iso-butyric acid> valeric acid> propionic acid> propanediol> lactic acid. However the mixture of these individual components administered as a naturally produced hydrolysate revealed the fastest methane production kinetics. Differences in the absolute values of determined kinetic parameters between the two experiments can be attributed to variations in organic loading rate (OLR), since degradation rates of a specific substrate are determined by substrate concentration. But also other parameters influence the absolute rate at which methane is produced, such as the concentration of products or unionized substrate itself, pH, nutrient availability, bioenergetics, temperature, inhibition, mass transfer and microbial population. In the third research paper "Demand-Driven Biogas Production in Anaerobic Filters "the previous findings have been put to the test by applying changes in OLR throughout the day and examining different substrate compositions with respect to the methane production rates. As demonstrated, the gas production followed the applied OLR with a distinctive expression of each change in the OLR. That marks the process as highly predictable and defined boundaries within safe operation of AD, in terms of VFA accumulation,can possibly be satisfied by process control. The inclusion of three reactors in the analysis emphasizes the repeatability and therefore the predictability of such an approach of operation. Feasibility and reproducibility of demand-driven biogas production by anaerobic filters could thus be demonstrated. It has been found that the hydrolysate composition has no significant influence on methane production kinetics for demand orientated gas production, since the maximum rate is limited by acetoclastic methanogenesis. The control of the hydrolysis should focus on high overall degradation, rather than towards the production of specific intermediates. A key factor in order to prevent large fluctuation in gas composition is alkalinity, specifically the provision of nitrogenous compounds is vital to maintain stable conditions. Anaerobic filters or attached biomass reactors in general seem to exhibit superior performance towards shock loading and are therefore especially suited for demand orientated gas production as they recover quickly from overloading.Formation of soluble microbial products (SMP) and extracellular polymeric substances (EPS) may be influenced or exaggerated by constantly changing HRT and OLR. Further research in order to evaluate the limits of safe operation is recommended as more extreme scenarios than the ones examined in this work are imaginable in practice.
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    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.
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    Effects of monensin and tannin extract supplementation on methane production and other criteria of rumen fermentation in vitro and in long-term studies with sheep
    (2013) Wischer, Gerald; Rodehutscord, Markus
    Ruminants increasingly attract public concern due to their methane release and contribution to the greenhouse effect. One strategy to reduce the release of methane is to modify microbial fermentation in the rumen by the use of feed additives such as monensin and tannin extracts. However, other characteristics of fermentation including the synthesis of microbial protein may also be affected. The aim of the present studies was to provide a comprehensive evaluation of the effects of monensin and tannin extracts on ruminal fermentation and methane production. The ionophore monensin is known to increase feed efficiency in ruminants. Although the use of silages is common practice in cattle feeding, the effects of monensin on the fermentation of silages in the rumen and microbial protein synthesis are lacking. Monensin has often been described to have indirect effects on methane production resulting from its effects on feed intake, protozoa and Gram-positive bacteria. It has rarely been studied whether monensin can reduce methane production without adverse effects on other criteria of rumen fermentation. The first objective therefore was to investigate the effects of different dosages of monensin on methane production and microbial protein synthesis when supplemented to different silages in two in vitro systems (Study 1). In Experiment 1 of Study 1, 15 g of oven-dried grass silage alone or combined with a concentrate was incubated in a rumen simulation (Rusitec) over a period of 13 d to examine the effects of monensin supplementation (2 or 4 mg/d, n = 4) on the production of total gas, methane, volatile fatty acids (VFA), degradation of nutrients and microbial protein synthesis. In Experiment 2 of Study 1, different dosages of monensin (0.5, 1, 2, 6 and 10 µg) were supplemented to syringes containing 120 mg of grass silage alone, grass silage combined with concentrates, or maize silage alone. After 24 h of incubation the effects of monensin on total gas, methane and VFA production were determined. In Experiment 1 monensin inclusion to grass silage and grass silage combined with concentrate resulted in a decreased total gas, methane and acetate production, while propionate production was increased. Along with a decreased degradation of crude protein, ammonia concentration in the system was reduced. While microbial protein originating from solid associated microbes decreased with monensin inclusion, microbial protein from liquid associated microbes was increased, resulting in an increase in total microbial protein synthesis. In Experiment 2, different dosages of monensin reduced methane production in grass silage (17%), grass silage combined with concentrate (10%) and maize silage (13%) without adverse effects on total gas production. Based on these two in vitro experiments it was concluded that monensin is able to reduce methane production without a major decrease in total gas and VFA production and degradation of organic matter. Although microbial fractions were differently affected, the total microbial protein synthesis was increased upon monensin supplementation. Tannins are secondary plant compounds that are known to complex with feed and microbial proteins. Several products from this heterogeneous group have shown potential to affect rumen fermentation in vivo and, even more, in vitro, but are often accompanied by negative effects on digestibility, feed intake and microbial protein synthesis. In Study 2 of the present work, ten tannin extracts (chestnut, mimosa, myrabolan, quebracho, sumach, tara, valonea, oak, cocoa and grape seed) and four monomers of rapeseed tannin (pelargonidin, catechin, cyanidin and sinapinic acid) were screened in grass silage based diets in successive runs using the Hohenheim Gas Test. The objective was to determine the optimal dosage of each tannin extract to cause a maximal methane reduction without negative effects on total gas production. Whereas the supplementation of pelargonidin and cyanidin to grass silage did not reduce methane production; catechin and sinapinic acid reduced methane production without affecting total gas production. Except tara extract, all tannin extracts reduced methane production by 8 to 28% without adverse effects on total gas production. Based on these results, chestnut, grape seed, myrabolan, sumach and valonea extract were investigated in a second step in a Rusitec to determine their effects on degradation of nutrients, VFA and ammonia production, and particularly on microbial protein synthesis. All tannin extracts were supplemented at similar dosages of 1.5 g to 15 g of grass silage. The supplementation of chestnut resulted in the greatest decrease in methane production (63%), followed by valonea (35%), grape seed (23%), sumach (18%), and myrabolan (7%; not significantly different from the control). While chestnut extract reduced acetate production by 19%, supplementation with grape seed or myrabolan extract increased acetate production; however, degradation of fibre fractions was reduced in all tannin treatments. Degradation of dry and organic matter was reduced by all tannin extracts, but there were no differences between tannin treatments. Crude protein degradation and ammonia production were also reduced by tannin extract supplementation. Microbial protein synthesis and its efficiency were not affected by tannin supplementation, which indicates that a reduction in methane production due to tannin extract supplementation is possible without negatively affecting microbial protein synthesis. Chestnut and valonea extract had the greatest potential in reducing methane production without negative effects on rumen fermentation of grass silage and microbial protein synthesis. Therefore, these tannin extracts were investigated for their long-term effects in sheep (Study 3). In Experiment 1 of Study 3, sheep receiving the control, chestnut or valonea treatment (each n = 4) were fed 842 g/d of hay (fresh weight). The animals on the control treatment also received 464 g/d of concentrate, and animals on the tannin treatments received the same amount of concentrate but were also fed 20 g of the respective tannin extract. Following initiation of tannin feeding, methane release from sheep was measured in 23.5 h intervals in respiration chambers on day 1, 8, 15, 29, 57, 85, 113, 148, and 190. In three balances periods faeces and urine were collected for 6 and 3 days, respectively. Effects on nutrient digestibility, nitrogen and energy metabolism were evaluated, with microbial protein synthesis estimated from the urinary excretion of purine derivatives. Based on the results of Experiment 1, a second experiment was conducted four month after the start of Experiment 1. Experiment 2 had the same study design and data collected, but the dosage of tannin extracts was doubled compared to Experiment 1 (0.9 vs. 1.7 g tannin extract/kg body weight) and the duration was shorter (85 days). Hay and concentrates used in both experiments were also evaluated using the Hohenheim Gas for their effects on total gas and methane production. In both experiments, methane release was not significantly reduced by tannin extract supplementation when analysed over the whole experimental period. In Experiment 1 the supplementation of chestnut extract on day 190 resulted in a reduced methane release. In both experiments, on day 1 a numeric reduction in methane release for the tannin treatments was observed, with a greater reduction recorded for the higher dosage used in Experiment 2. This trend disappeared by day 57. In the third balance period of Experiment 1, digestibility of dry and organic matter was reduced by tannin supplementation. The digestibility of crude protein was reduced in both experiments, whereas the digestibility of fibre fractions was not influenced. In both experiments a long-lasting shift in nitrogen excretion from urine to faeces was observed, which occurred to a greater extent in Experiment 2. The urinary excretion of purine derivatives was not significantly affected by tannin supplementation, indicating that the microbial protein synthesis was not altered in either experiment. The in vitro methane production was reduced for concentrates containing tannin extracts, but it was not significantly affected when concentrates were incubated with hay. It is concluded that monensin added to different silages caused a decrease in methane production without affecting total gas production but with an increased microbial protein synthesis. Nine of the ten considered tannin extracts and two tannin monomers decreased methane production without affecting total gas production. The Rusitec study confirmed the great potential of chestnut and valonea extract to reduce methane production without negative effects on microbial protein synthesis. However, neither chestnut nor valonea extract reduced the methane release in sheep when fed over a longer period of time. It is assumed, that rumen microbes adapted to the tannin dosages in terms of methane release but not nitrogen metabolism, as there were long-lasting effects on nitrogen excretion. The shift in nitrogen excretion can have a positive effect on the environment due to the reduced potential of ammonia emission from the urine. Both in vitro systems used in the present studies showed effects of tannin extracts that were considerably different from those observed in sheep. The monomers investigated in the present study are the basic units of condensed tannins, whereas the tannin extracts selected in vitro only contain hydrolysable tannins. It is possible that monomers of chestnut and valonea extract may reduce methane production, whereas higher dosages of these tannin extracts cause negative effects on feed intake, digestibility and microbial protein synthesis. Further investigations should focus systematically on the transfer of in vitro studies to estimate in vivo responses. Therefore, a parallel implementation of different in vitro and respiration studies would be of great value.
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    Effects of nitrification inhibitors and application technique on trace gas fluxes from a maize field after cattle slurry fertilization
    (2019) Herr, Christina; Müller, Torsten
    In a time of climate change and against the background of intensive animal husbandry and biogas production in Germany, strategies for mitigation of greenhouse gas (GHG) release and Nitrogen (N) losses from silage maize production become increasingly important, especially for organic fertilizers. Consequently, the main objective of this study was to determine the height of GHG release from silage maize production on a medium textured soil which is typical for this region in Southwest Germany and to evaluate useful fertilization opportunities to mitigate carbon dioxide (CO2) footprint per yield unit. To identify management factors improving GHG budget from silage maize, annual nitrous oxide (N2O) and methane (CH4) measurements were carried out during maize growth and subsequent black fallow at least weekly. Investigations were conducted over two years on two adjacent fields (one for each study year). Amounts of ammonia (NH3) volatilizations after fertilization and nitrate (NO3-) leaching losses were also included in GHG balances. In dependence on available data, determined or estimated values were used. Additionally, yield and N removal from maize plants were quantified. The basic treatments of this study which investigated impact of fertilizer form and application techniques, were an unfertilized control (CON), a mineral fertilization (MIN), a banded cattle slurry application by trailing hose and subsequent incorporation (INC) and a cattle slurry injection (INJ). As confirmed repeatedly, in contrast to broadcast slurry incorporation, slurry injection efficiently reduced the risk of NH3 losses by direct slurry placement into the soil, but simultaneously provoked N2O formation more strongly, probably due to the anaerobic conditions in the injection slot favoring denitrification. For reducing N2O release from slurry injection, the applicability of six single or combined nitrification inhibitors (NIs) concerning potential GHG reduction were investigated. This N2O reduction should be reached through the desynchronized availability of carbon (C) and NO3-, derived from nitrified slurry ammonium (NH4+). Thus, in the period after slurry application, N2O losses from denitrification as well as from nitrification should be reduced through NIs. For final evaluation, collection of measured and estimated data (including direct and indirect N2O losses (NH3, NO3-), CH4 budget, pre-chain emissions from mineral fertilizer and fuel consumption) were converted into CO2 equivalents and summarized as area- or yield-related GHG balances. Except for one of the INJ treatments with NI (exclusively investigated in the first year) and one INC treatment with NI (exclusively investigated in the second year), all remaining treatments were tested in both experimental years. The height of NH3 emissions from INC treatment (12-23 % of applied NH4+-N) was more weather-dependent than those from INJ treatment (12-15 % of applied NH4+-N). In mean over both years, cumulative N2O emission from INJ treatment (13.8 kg N2O-N ha-1 yr-1), was significantly higher than from CON, MIN, and INC which recorded 2.8, 4.7, and 4.4 kg N2O-N ha-1 yr-1. NIs decreased the fertilization-induced N2O emissions from injection by 36 % (mean over all NIs and years) by an order of magnitude comparable to slurry incorporation. The NIs investigated tended to be categorized in inhibitors with prior and delayed inhibitory maximum. Whether low persistence, or poor biological degradability was an advantage, depended on environmental conditions. A combination of two NIs, one with putative prior and one with delayed release behavior reached the highest N2O reduction. In the additional INC treatment, this NI combination tended to reduce annual N2O release by 20 % in comparison to incorporation without inhibitor. Beside the potential of reducing fertilization-induced N2O emissions, NIs might also help to improve CH4 budgets in silage maize production. In general, CON, MIN and INC were net CH4 sinks in both years with mean uptakes of 460, 127, and 793 g CH4-C ha-1 yr-1, respectively. Conversely, slurry injection resulted in net CH4 emissions of 3144 g CH4-C ha-1 yr-1 (mean over both years). However, NIs tended to reduce CH4 emissions from injection by around 48 % and increased CH4 consumption from slurry incorporation by 20 %. Across all treatments and years, direct N2O emissions were the major contributor to total GHG balance. Yield-related GHG budgets from both years were lowest for CON, followed by INC or MIN treatment and significantly highest for sole slurry injection. NIs decreased fertilization-induced GHG release from injection in mean over both years by order of magnitude comparable with slurry incorporation. Consequently, alongside slurry incorporation and broadcast mineral fertilization, slurry injection combined with recommended NIs was evaluated as an equally appropriate fertilization strategy in terms of the atmospheric burden for livestock farmers.
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    Greenhouse gas emissions from rice production in the Vietnamese Mekong River Delta as affected by varietal selection and water management
    (2023) Vo, Thi Bach Thuong; Asch, Folkard
    The topic of this dissertation deals with rice production, the predominant source of daily nourishment for more than half of the worlds population. Rice production is directly affected by global climate change through aggravating climatic conditions, but is also one of the major sources of greenhouse gases (GHG) in the agricultural sector. The latter aspect is investigated in 4 publications by assessing the factors contributing to emissions, the quantification of GHG emissions across different scales, and possible mitigation of GHG emissions. In totality, these studies aim at bridging the gap between field measurements to national extrapolations in view of both GHG inventories and future mitigation programs. In terms of methodologies, the publications compiled in the following chapters represent a broad spectrum ranging from field measurements to meta-analysis, but they all deal with the emission of methane (CH4) which is generated in rice fields due to the unique feature of ‘semi-aquatic’ soils. The publications based on newly conducted field measurements also a nitrous oxide (N2O) which is a potent GHG emitted typically emitted from rice fields in low quantities. Chapter 2 (Vo et al. 2018) compiles field measurements from the Vietnamese Mekong River Delta (MRD) which accounts for more than 50% of the country’s rice production. Emission factors (EFs) are used to estimate total emissions associated with the area of rice production. The Intergovernmental Panel on Climate Change (IPCC) has given the default EFs that are based on global averages as Tier 1 approach. However, the IPCC guidelines encourage national reporting institutions to conduct field measurements of GHG emissions and to determine country-specific EFs as the basis of the Tier 2 approach. Tier 2 further accounts for the fact that emissions may also be highly variable within a given country by requesting for disaggregation of EF at a sub-national scale. Therefore, the most recent GHG inventories for Vietnam are based on region-specific EFs under the IPCC Tier 2 approach, which is implemented using national activity data (i.e., national average cultivation period of rice and harvested area). In Chapter 2, we developed the specific EFs for different hydrological sub-zones and growing seasons in the MRD to achieve disaggregated EFs that could be used for the National Communications submitted to the United Nations Framework Convention on Climate Change (UNFCCC). Due to the distinct bio-physical condition and cropping cycle, the results show the lowest emissions in the saline sub-zone. While alluvial, acid sulfate soils had intermediate levels, the highest emissions were found in the deep flood sub-zone. In Chapter 3 (Vo e al. 2018), we expanded the geographical scope of the GHG assessment to the entire country. This meta-analysis of CH4 data covers 73 cropping seasons at 36 field sites across the rice-growing areas of Vietnam under the IPCC’s baseline conditions (i.e., continuously flooded, no organic amendments) in the three main cropping seasons. As an output of this study, a structured database contained the location and season of each measurement as well as site-specific bio-physical factors and crop management at the site scale. In the next step, we developed disaggregated EFs for different zones and cropping seasons across the country that can be used for future reporting commitments of Vietnam as part of a more accurate Tier 2 assessment. The calculated EFs were generally higher than the IPCC defaults and the values used for Vietnam’s 3rd National Communications for the North, Central, and South Vietnam. Chapter 4 (Vo et al. 2023) has to be seen in the context of Vietnam’s climate change policy that aims at reducing GHG emissions from rice production. Mitigation in rice production will be crucial for Vietnam because CH4 from rice accounts for about 15 % of the national GHG which is more than the entire transport sector even without considering CO2 and N2O emissions along the rice value chain. Previous studies have assessed the potential practices by changes in farming practices, namely water, nutrient, and straw management, and almost uniformly concluded that Alternate Wetting and Drying (AWD) is the most promising strategy for achieving a sizable mitigation of GHG emissions. Given the intense rainy season in southeast Asia, however, the precipitation is often too high to implement this water regime and will not provide any economic benefit from water saving. In turn, it is important to consider other mitigation strategies such as the selection of low-emitting cultivars. We conducted a field screening of 20 rice varieties that was expanded by assessing the interactive effect of variety selection and AWD. An experimental layout with 120 plots (based on 3 replicates) was required to assess this interaction of variety and water management in the field using the closed chamber method to collect air samples followed by lab analysis (using a gas chromatograph) to quantify the CH4 and N2O concentrations. The results of this study confirmed that GHG emissions from rice fields are dominated by CH4 emissions whereas N2O emissions were negligible. Compared with IPCC default values, the data set from two dry seasons yielded higher emissions under a baseline of continuous flooding (EF = 2.96 kg CH4 ha-1 d-1) and lower Scaling Factors (SF) of AWD (SF = 0.4). Chapter 5 (Asch et al. 2023) deals with the agronomic aspects of both AWD and variety selection and their implications on the economic viability of future mitigation efforts. While AWD is more efficient in reducing CH4 emissions than variety selection, this water management practice resulted in a slight yield decrease in our field study. Given the limited applicability of AWD, the selection of varieties is a much more adaptable approach and is also beneficial in terms of farmers’ adoption because it does not require any crop management changes. However, this strategy could also impact profits since the lowest-emitting variety may not have the highest rice yields. In the context of future mitigation programs in the MRD, the dry season allows good control of the water table, so AWD should be the core of any mitigation effort. Variety selection on the other hand should be targeted in those seasons and locations that do not allow draining the fields. In turn, low-emitting varieties should become an integral part of future mitigation programs to supplement AWD within a systematic out scaling. In terms of economic trade-offs for the farmers, we assumed a scenario with compensation derived from the still premature carbon markets. The potential profit increments are very low and not attractive if distributed to farmers directly, but may collectively be used for investments in rural development by government agencies for benefitting farmers indirectly, e.g. by improving the irrigation infrastructure.
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    Optimierung der primären Gärung bei zweistufigen Biogasanlagen
    (2016) Lindner, Jonas Philipp; Jungbluth, Thomas
    The microbial conversion of biomass into biogas generally comprises several steps. These steps, are divided in accordance to the involved microorganisms and are often referred to as primary fermentation, secondary fermentation and methane formation. In contrast to single-stage, two-stage biogas system performs primary fermentation spatially separated from the methanogenesis in order to provide optimal milieu conditions for each group of microorganisms. There are many different reactor settings outlined in scientific literature for two-stage biogas production. For the digestion of energy crops or biowaste, discontinuously charged leach-bed reactors are often combined with anaerobic filters. The main disadvantage of this setup is the impossibility of regulating the pH-value in the first step, thus leading to fluctuating acid and gas production rates. To avoid this, new approaches aim to use continuous flow stirred-tank reactors for the process of primary fermentation, using chemical additives for the pH regulation. In the framework of this research, a process automation for a continuous two-stage system was developed and implemented in two lab scale plants at the State Institute of Agricultural Engineering and Bioenergy. Each laboratory plant comprised of a continuous stirred-tank reactor with an integrated filtration for solid-liquid separation and an anaerobic filter. In the primary fermentation stage, the adjustment of the pH-value was made by an indicatorbased return of alkaline effluent from the anaerobic filter. In order to evaluate and optimize the newly developed and completely automated pH-regulation system, this study investigated the (I) influence of the substrate characteristics on the degree of degradation and the biogas yields, (II) optimal pH-value for biomass degradation in the primary fermentation and (III) the possibility of enhancing methane yields by combined mechanical and enzymatic treatment of digestates with a subsequent refeeding into the process. The results of the investigations clearly showed the suitability of the system for a highprecision pH-regulation in primary fermentation for the tested pH-values 5.5, 6.0, 7.0 and 7.5. This unique technique enabled the continuous formation of organic acids and biogenic gases. Hay/straw, maize silage and sugar beet silage were digested at a pH-value of 5.75 in order to investigate the influence of different substrates on the two-stage system performance. Compared to the determined potential biogas yields, the recorded methane yields were 70.6 % lower for the hay/straw substrate and 31.3 % lower for maize silage in the two-stage system. Contrary to this, for sugar beet silage no difference in the gas yields between the batchtest and the two-stage system could be detected. Further investigations on the influence of pH-value on the degradation rate of lignocellulosic substrates showed an optimum pH between 7 and 8. The mechanical treatment of the digestates with the ball mill exhibited no losses of volatile solids through warming. The application of this procedure enhanced the specific methane yield from 9 to 17 % for maize silage digestate and hay/straw digestate respectively from the described laboratory plant. The treatment of the digestate obtained from a full-scale plant permitted a triplication of the specific methane yield at very low level. The combined mechanical and enzymatic treatment through the aerobic fungi “lentinula edodes” resulted in losses of volatile solids between 58.2 and 86.4 % for the hay/straw digestate and between 10.8 and 18.4 % for the substrate from the full-scale biogas plant depending on the incubation time. Furthermore, the investigations determined an increase in the lignin content of the hay/straw digestate by the combined treatment. Overall, using the digestate of the two-stage system, the mechanical/enzymatic treatment attributed to a methane yield loss by 86.4 %. In contrast, an increase of methane production by 134.5 % was observed with the full-scale digestates. This study has revealed that two-stage biogas systems are favorable only for easily degradable substrates. The phase separation was not beneficial for fiber rich substrates. Based on the results, a reactor cascade consisting of a continuous stirred-tank reactor and an anaerobic filter with similar milieu conditions seems to be well suited for the digestion of organic wastes. Due to the extraordinary high process stability, flexibility and high load capacity this system is very suitable for the treatment of substrates with extremely varying compositions. Moreover, within the study essential basics for the application of innovative fermentation procedures (e.g. pressure fermentation) were investigated. The combined mechanical and enzymatic treatment of digestates seems to be an interesting alternative to the established substrate pretreatment systems and it can be recommended also for single-stage biogas plants.
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    Production of lactic acid and methane from renewable resources : an innovative green biorefinery concept for biogas process chains
    (2015) Haag, Nicola Leonard; Jungbluth, Thomas
    The increasing demands of world’s growing population for food, energy and products, the effects of climate change and the depletion of fossil resources forces the development of sustainable industries. Based on renewable resources, state-of-the-art processes have to be transformed to eco-friendly production sequences to lead the industry to a new, bio-based economy. An essential part of the bio-based economy will be biorefineries, as they enable the production of goods and energy from bio-based resources. The aim of this study was to establish an innovative green biorefinery concept to optimize biogas process chains. The green biorefinery concept was set up to both utilize and add value to green biomass, as well as other common raw substrates used in biogas processing, by producing platform chemicals and biogas. New ensiling techniques were applied, in order to increase the amount of valuable ingredients in the silage with a special focus on lactic acid. After solid-liquid separation of the silage to exploit organic acids, the solid residue was used for anaerobic digestion. In particular the objectives were: (1) to clarify which valuable chemicals can be increased in significant amounts, depending on the raw substrate, (2) to examine the technical, chemical and biological parameters affecting the increase of valuable products in the silage and (3) to investigate the methane formation potential of the residual biomass and the fresh silage to identify potential methane losses. Lactic acid was the most promising chemical, increased to highest amounts during the ensiling process. The addition of carbonated lime was the most effective treatment to increase the amount of lactic acid, requiring a high fermentability coefficient of the utilized raw substrate. Additional lactic acid producing bacteria can help to stabilize the silage and promote the growth of lactic acid contents. Supplying the lactic acid bacteria with additional trace elements (manganese) showed no effect on lactic acid production. The comparison of specific methane yields of the fresh silages with the corresponding solid residues always yielded higher values for the fresh silage (not always significant), due to the loss of volatile solids during the fractionating. Furthermore, there is a loss of overall methane production, due to the reduction of mass while fractionating. An initial economic assessment revealed that selected variations of the treated raw substrates maize and grass offer a huge potential for the presented biorefinery concept, as the increase in lactic acid contents was immense while simultaneously having no significant losses in specific methane yields. Crucial importance for the economic feasibility lies on the downstream process of lactic acid. Future research has to be focused on establishing adequate extraction techniques, as the extraction and purity of lactic acid is the primary challenge for the economic viability of the concept. In the context of adding value to existing biogas process chains, the presented green biorefinery concept is an alternative conversion path of biomass and will likely be of monetary interest in the near future. Moreover, the improved silages can be beneficial in other applications, such as the production of middle chain fatty acids for further processing. The presented biorefinery concept is of high value for numerous applications and shows an improved method of green biorefining, which can contribute to leading our society and industry to a sustainable and multifaceted future.
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    Die Rolle des Porenraums im Kohlenstoffhaushalt anthropogen beeinflusster Niedermoore des Donaurieds
    (2007) Höll, Bettina; Stahr, Karl
    The use of peatlands in Central Europe for hundreds of years has led to their degradation (loss of organic matter) due to intensive mineralisation. Re-wetting of formerly drained peat aereas has been a popular method of retaining existing peatlands. The effect of re-wetting of degraded fens on their C-pools and C-fluxes is unknown. The protection of these natural resources combined with the creation of biological C-sinks might render the protection and conservation of peatland ecosystems more attractive. Water-logging leads to the accumulation of water in previously air-filled soil pores, something that might increase the C-pool of the soil. It is unknown whether the pore space, which possibly accounts for up to 90% of peatlands, contains carbon components that are similar to those found in the solid soil substance. It is also unknown how much the utilisation of peatlands affects the composition of C-components of the pore space. The major objectives of the present study were (1) to assess the temporal and spatial variability of the C-components in the pore space in fens undergoing different anthropogenic use (drainage, re-wetting) and (2) to assess the role of the pore space in the C-budget. In a Southern German area known as the Schwäbisches Donaumoos, carbon components of the gaseous phase (CO2, CH4) and the liquid phase (CO2/DIC, CH4, DOC, POC) were collected at different depths (5, 10, 20, 40, 60, 80 cm) from different drained (deep, moderately) fen sites and from a long-term re-wetted fen site. Sampling was done at weekly intervals between April 2004 and April 2006. The samples of the water phase and gas phase were collected at the respective sites using slotted PVC tubes and soil-air probes. Gas was analysed using a gas chromatograph and dissolved organic carbon was analysed using a TC water analyser. The fen sites were characterised by selected static parameters of the solid substance and dynamic parameters such as redox potentials, temperature, water level, soil-moisture tension and pH value. The specific use of the fens, which is closely related to the water budget of the area, was a decisive determinant of the amounts of carbon in pore space. Although the solid soil substance in fen sites accounted for less of 10% of the total substance (solid + pores), it still contained a higher amount of carbon (60 -152 kg C m-3) than the pore space. Furthermore the amount of time that the carbon remains is eventually longer in the solid soil substance than in the pore water. Assuming the pore water works only as a short time reservoir. Filling of the pore space with either air or water had a decisive effect on the amount of C. The investigations showed that the amount of C in the air-filled pore space contained an annual average of 15 g C m-3 (deep-drained area), whereas the water-filled pore space contained on average 263 g C m-3 (re-wetted area). The variable anthropogenic effects on fens led to area-specific situations (e.g. groundwater level) that not only affected the amount of C but also had a significant effect on the composition of C components. Dissolved inorganic carbon (DIC), with an average proportion of 55-72%, accounted for the largest proportion of dissolved carbon. Particulate organic carbon (POC) had similar concentrations to dissolved organic carbon (DOC), whereas dissolved methane (CH4) only accounted for a minor proportion (< 0.1%) of the entire carbon of the liquid phase. The DIC concentration was highest in the water from the pores of re-wetted fen. Independent from the use of the fens, different DIC isotope signatures of the ground, karst and spring waters (-11.7‰ to -14.3‰) in comparison to the pore waters (-16.7‰ to -18.4‰) were observed. The further differentiation into the 13C ratios of CO2 contained in the gaseous phase (-23.0‰ to -26.6‰) suggests that DIC ‘accumulated’ in the pore water by way of biogenic CO2. DOC concentrations were lowest in the re-wetted fen. The temporal variability of DOC was related to changes in the bioavailability of DOC. This was also observed in the moderately drained area. The low degree of aromatisation (= higher bioavailability) associated with higher DOC concentrations led to significantly lower values in the re-wetted area compared to the moderately drained area. The microbially easily available DOC proportion was not only temporally but also spatially limited and had a significant effect on the CO2 and CH4 concentrations. At similar depths, CO2 values 10- to 1000-fold higher than CH4 levels could be measured in the gaseous phase (2.7-67 mg CO2-C l-1 vs. < 5.3 mg CH4-C l-1). The highest concentrations were measured in the re-wetted fen. The CO2-C/CH4-C ratios rarely achieved ratios of below 100:1. Due to the higher concentrations of CO2, it can be assumed that the carbon dioxide could compensate for the effect of methane on the climate, on the condition that comparable CO2-C/CH4-C ratios are found in the emissions. The protection of fens as natural resources could be related to carbon uptake (results of the gas exchange to the atmosphere) and higher carbon amounts in the pore space. The amount of time that the carbon remains in the pore waters is correlated to carbon turnover and hydrological conditions. The latter are also important when assessing the indirect emissions, playing an important role in drained fens and rounding out carbon balances.
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    The role of Phragmites australis in carbon, water and energy fluxes from a fen in southwest Germany
    (2019) van den Berg, Merit; Streck, Thilo
    The global carbon emission from peat soils adds up to 0.1 Gt-C per year. Under anaerobic conditions, organic material is decomposed to methane (CH4). Over a 100-year cycle, methane is a 28 times stronger greenhouse gas than carbon dioxide and is an important factor for climate change. Therefore, there is a great interest to get a better understanding of the carbon flows in peatlands. Phragmites peatlands are particularly interesting due to the global abundance of this wetland plant (Phragmites australis, common reed) and the highly efficient internal gas transport mechanism. This is a humidity-induced convective flow (HIC) to transport oxygen (O2) to the roots and rhizomes, with the effect that simultaneously soil gases (CH4 and CO2) can be transported to the atmosphere via the plant. Thereby, Phragmites is expected to have a high evapotranspiration (ET) rate due to the large leaf area, open water habitat and high aerodynamic roughness. This ET could highly influence the hydrology of the system. Because he accumulation of organic material occurs because of limiting oxygen levels, hydrological processes are fundamental in the development of peatlands. The research aims were: 1) to clarify the effect of plant-mediated gas transport on CH4 emission, 2) to find out whether Phragmites peatlands are a net source or sink of greenhouse gases, and 3) to evaluate ET in perspective of surface energy partitioning and compare results with FAO’s Penman-Monteith equation. CO2, CH4 and latent and sensible energy fluxes were measured with the eddy covariance (EC) technique within a Phragmites-dominated fen in southwest Germany in 2013, 2014 and 2016. In 2016, a field experiment was set up to quantify the contribution of plant-mediated CH4 transport to the overall CH4 flux and how it influences ebullition. One year of EC flux data (March 2013–February 2014) shows very clear diurnal and seasonal patterns for both CO2 and CH4. The diurnal pattern of CH4 fluxes was only visible when living green reed was present. This diurnal cycle had the highest correlation with global radiation, which suggests a high influence of HIC on CH4 emission. But if the cause were HIC, relative humidity should correlate stronger with CH4 flux. Therefore, we conclude that in addition to HIC at least one other mechanism must have been involved in the creation of the convective flow within the Phragmites plants. We quantified the influence of pressurized flow within Phragmites on total CH4 emission in a field experiment (see chapter 3) and found between 23% and 45% lower total CH4 flux when pressurized flow was excluded (by cutting or cutting and sealing the reed). The gas transport pathways from the soil to the atmosphere changed as well. Relative contribution of ebullition to the total flux increased from 2% in intact Phragmites to 24-37% in cut vegetation. This increase in ebullition in cut vegetation, obviously, did not compensate the excluded pathway via the pressurized air flow at our site. It also means that the effect of CH4 bypassing the oxic water layer by plant transport on CH4 emission is much larger than the effect of O2 transport through the plants on CH4 oxidation and production in the rhizosphere. Overall, the fen was a sink for carbon and greenhouse gases in the measured year, with a total carbon uptake of 221 g C m-2 yr-1 (26% of the total assimilated carbon). The net uptake of greenhouse gases was 52 g CO2 eq.m-2 yr-1, which is obtained from an uptake of CO2 of 894 g CO2 m-2 yr-1 and a release of CH4 of 842 g CO2 eq.m-2 yr-1. Compared to the long term uptake of carbon by northern peatlands (20–50 g C m-2 yr-1) 212 g C yr-1 is therefore very high. One year of measurements is not enough to draw hard conclusions about the climate change impact of this peatland. The measured ET at our site was lower than other Phragmites wetlands in temperate regions. ET was half the amount of precipitation (see chapter 4). Therefore, the risk of the wetland to dry out is not realistic. ET was especially low when there was little plant activity (May and October). Then, the dominant turbulent energy flux was sensible heat not latent heat. This can be explained by the high density of dead reed in these months. the reed heats up causing a high sensible heat flux. Evaporation was low due to the shading of the water layer below the canopy and low wind velocities near the surface. FAO’s Penman-Monteith equation was a good estimator of measured ET with crop factors from the regression model of Zhou and Zhou (2009) (see chapter 4). Especially the day-to-day variation was modeled very well. Their model had air temperature, relative humidity and net radiation as input variables. This is likely related to stomatal resistance, which depends on the same variables. Therefore, the model of Zhou and Zhou (2009) is an interesting tool for calculating daily crop factors and it is probably robust enough to be used also in different regions.
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    Two-stage high pressure anaerobic digestion for biomethane production
    (2017) Merkle, Wolfgang; Jungbluth, Thomas
    The use of natural gas for power and heat generation in the EU has become particularly prominent since the 1990s. As a result, the whole natural gas infrastructure has been continuously expanded and today has a total length of 2.15 million km and a storage capacity of about 108.3 billion m³. The production of biomethane in the EU and its distribution by natural gas network offers an interesting alternative for the reconfiguration of EU’s energy supply system. Up to now, biomethane is obtained by purifying and upgrading raw biogas in a complex process. In this study, a novel two-stage high pressure anaerobic digestion system was developed. This innovative concept aims to integrate biogas production, purification and pressure boosting within one system. The process is based on the enhanced water solubility of carbon dioxide compared to methane. By operating the methane reactor for biogas production at increased pressures, high amounts of dissolved carbon dioxide can be removed with the liquid effluent from the reactor, resulting in a high-calorific biogas. In batch experiments at pressures up to 30 bar, a significant influence of pressure on the pH-value in the reactor was observed, due to the augmented formation of carbon hydroxide. The study on the effect of a rapid pressure increase up to 100 bar showed no inhibition of the microorganisms in the batch-rigs too, although the microorganisms were not adapted to these environmental conditions. Furthermore, a continuously operated methane reactor was run at pressures up to 50 bar for the first time. The experiments showed that a stable anaerobic digestion process could be run at these pressures nearly without any problems and methane contents above 90% could be achieved. The promising results showed that this technology has great potential in producing on-site high calorific gas also in smaller units. In addition, the costs of post-production gas purification can be significantly reduced, due to the fact that the size of a subsequent gas purification unit can be decreased. Furthermore, the produced gas can be injected into the transnational gas grids without post pressurization or can be used in the transportation sector.
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    Untersuchungen zum Emissionsgeschehen von Ammoniak und Methan in der Mastschweinehaltung
    (2017) Gronow-Schubert, Stephanie; Gallmann, Eva
    The growing of feed crops, the production of farm livestock and the processing of livestock products, along with the associated use of farmland for this entire production chain, all engender greenhouse gases on a worldwide scale. In this respect, ammonia and methane emissions are directly associated with livestock farming including the feeding of pigs for slaughter. The main aim of the work presented in this thesis was investigation of emissions produced in this way, and into selected strategies applied for reducing ammonia and methane release, particularly in management of liquid manure inside a fattening unit. In this context, the paper focusses on the three approaches – measuring, analysing and modelling - which are accordingly established as the following part-targets: • Applying emission reduction strategies as part of liquid manure management in a conventional fattening unit and comparing the resultant emissions with those from a reference system where no emission reduction actions had been taken. The selected emission reduction strategies should be practicable and sustainably applicable in existing livestock housing systems. • Analysing the main factors of influence on emissions throughout the fattening period during different seasons of the year, with special consideration of time series effects and regressions. • Examining the possibilities of substance flow modelling, application to own measurement data rather or for assessing the potential of emission reduction methods as well as evaluation of the selected approach for substance flow modelling. In-barn liquid manure management with fattening pigs markedly influences ammonia and methane emissions whereby the concrete reduction potentials are not yet sufficiently clarified. Within this study, a first work package compares, through a case control approach, the liquid manure management strategies - weekly emptying of the liquid manure channel as well as covering of the underfloor stored liquid manure surface as well as the addition of Effective Microorganisms to the liquid manure – with the strategies tested for emission reduction potential and compared over a feeding cycle in each case with the stored manure method as reference. The pig housing used in the trial was divided into two compartments (experimental and reference compartment) each holding 50 animals. In quasi-continuous measurement, incoming air, compartment and exhaust air ammonia and methane concentrations, temperatures of incoming air, compartment and exhaust air, and the temperature and pH of the liquid manure, were all recorded. Additionally, liquid manure samples were analysed in 14-day rhythm and the level of liquid manure measured as well as the degree of dirtiness of pen floors. Also recorded were pig weights and performance or feeding data. No further differences in terms of feeding, ventilation or management existed between trial and reference compartments. The applied reduction strategies were able to partially reduce ammonia and methane emissions (weekly emptying of liquid manure channel: methane emission rates reduced by 39 % based on emission rate in grams per day and livestock unit; liquid manure cover: 13.8 % ammonia emission rates reduction in grams per day and livestock unit), had in part no effect, or even a negative influence on the emissions (weekly emptying of the liquid manure channel: no effect on ammonia emissions; liquid manure cover: 119.9 % rise in methane emission rates in terms of grams per day and livestock unit). The selected interval of one week between emptying the liquid manure channel was not sufficient as a reduction strategy. With covering of the liquid manure surface underfloor, it is important to consider that the almost airtight sealing of the liquid manure surface delivered favourable conditions for methanogenesis. The influence of the addition of Effective Microorganisms to the liquid manure on the emissions of ammonia and methane was marginal. The emissions of ammonia increased of 8.3 % and the emissions of methane of 5.9 %. The evaluations (time series and regression analyses) of the data from the reference compartments from a total of four feeding cycles (two summer and two winter cycles) comprised the second work package. The time series analysis enabled insight into the relationships between the ammonia and methane emissions in terms of time, and insights into the influential factors affecting release and transport of the gases. For example, the time-related influences of high temperatures on the system “fattening unit” and on the release of emissions, could be graphically shown. The time series analysis gave indications as to how dynamic, or how stable, climatic conditions can be in pig housing. The regression analyses clearly showed that the emission process, with ammonia as well as with methane, is influenced particularly through the amount of liquid manure involved, the temperature and the air volume flow. In the same way, the distance between the liquid manure surface and the slatted flooring (‘headspace’) was found to have direct influence on the release of ammonia and methane from the liquid manure. A larger ‘headspace‘ correlated with reduced emissions and vice versa. Following recording and statistical evaluation of the emission data, the contribution that can be made through substance flow modelling of ammonia emissions towards increasing knowledge on the emission process and on methods for its reduction within pig housing was examined as a third work package. This involved the transfer of selected recorded data into the substance flow model. Serving as basis was the model from CORTUS et al. (2010a) adapted in three steps to take account of the conditions in the pig housing being used. The constructional outline of the trial livestock housing served as system limit. Berkeley Madonna 8.3.18 software was used for numerical integration of the differential equation system. Own data was applied for calibration and validation, in each case taken from the reference compartment of two different feeding cycles. In principle, the adapted model was capable of modelling ammonia concentrations and emissions. In addition, the influence of the liquid manure temperature and pH value of the liquid manure could be depicted. However, the model generally reacted sensitively to temperature and pH values. Because of this, the model underestimated and overestimated recorded values, in part substantially. An important influence on the model accuracy appeared to be related to the submodel considering urine puddles. For the purposes of own modelling, this submodel was cut out of the main model during its adaptation according to the recorded data. Compared to recordings, modelling of gas concentrations and emissions offers the advantage of cost-efficient and time-saving estimations of emission potential for different housing systems, e.g. for feeding pig production. Calibration and validation, as well as adaptation to suit the type of application requires, however, particular care and expertise. Through the various methods for measurement, analysis and modelling that were applied, the work reported here contributes to better understanding of the emission process and the reduction of emissions, particularly in the case of liquid manure management in feeding pig production.