Agricultural Engineering Research, Volume 6 (2000)

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Possibilities and Limits of the Use of Thermography for the Examination of Horticultural Products
(2000) Linke, Manfred; Beuche, Horst; Geyer, Martin; Hellebrand, Hans Jürgen
As a result of complicated heat- and substance exchange processes be- tween the produce and the environment after harvest, the temperature on the surface of fruit and vegetables is generally lower than the air tem- perature. Infrared thermography systems allow the distribution of these surface temperatures to be measured. Temperature differences are made visible in the form of colour differences and evaluated with methods of computer image analysis. The present contribution shows the possibili- ties and limits of the use of thermal imaging systems for examinations of quality changes of horticultural produce at the postharvest stage. In principle, such thermal imaging systems are able to measure produce properties connected with thermal processes (transpiration, respiration). They may lead to qualitatively new insights and thus make a contribution towards quality maintenance. When interpreting the results, the interrelation between the produce and its environment must always be taken into account.
Environmentally Compatible Fattening Pig Husbandry I - Sensitivity of Emission Measurements
(2000) Gallmann, Eva; Hartung, Eberhard; Jungbluth, Thomas
At the Institute of Agricultural Engineering of the University of Hohen- heim, a swine housing system with fully slatted floor (FSF) and a freely ventilated kennel housing system (KHS) are being compared as part of continuous emission measurements with the goal of assessing the envi- ronmental impact of fattening pig husbandry systems. To secure the re- liability of the data, it is first necessary to examine the quality of the measurement, the methodological approach, and the execution of the tri- al. Subsequently, the criteria for data selection are determined taking the sensitivity of the emission measurements into account before the data are used for a comparison of the emission rates. When measuring the gas concentrations of ammonia (NH3 ) and methane (CH4 ), a water vapour cross sensitivity of the measuring instruments of 0.23 and 0.65 ppm/g H2 O/kg of air respectively must be taken into ac- count. Especially in the case of CH4 , this closely restricts the usability and significance of low concentration values if the water content of the sample air ranges between 10 and 20 g/kg of air. A comparison of the carbon dioxide (CO 2 ) concentration at two heights with the background concentration allows currents of leaking air at the air inlet of the natu- rally ventilated housing system to be detected with high temporal reso- lution. For these periods, it is impossible to determine the emission ra- tes. When the course of the gas concentrations in the slurry store is con- sidered, the kennel housing system shows an influence of the inlet air temperature on the air exchange through the slatted floor. The CO 2 con- centrations observed in both systems indicate that, as compared with the animal-specific portion, conversion processes in the excrement are re- sponsible for a larger part of the gas release than previously assumed.
Simulation of Threshing and Separation Processes in Threshing Units
(2000) Miu, Petre I.; Kutzbach, Heinz Dieter
For a better understanding of threshing and separating processes and for further increase of the performance of modern combine harvesters two universal stochastic mathematical models quantifying the grain and material other-than-grain (MOG) in the threshing and separation processes in both tangential and axial threshing units are presented. One model describes the percentages of unthreshed grain, free grain and se- parated grain over the length of threshing space: concave or rotor length. Threshing loss and separation loss can also be predicted. For axial threshing units have been developed generalized functions that al- low to predict the influence of crop properties and functional and design parameters on the above-mentioned process indices. The second model quantifies the cumulative percentages of separated MOG, separable MOG and unfragmented MOG (stems). Very good agreement of predic- ted and experimental data showed the validation of presented models.
A DGPS-Based Safety System for Agricultural Machinery
(2000) Klee, Ulrich; Hofmann, Lutz
When DGPS technology for the localization and navigation of vehicles became available, investigations were initiated at the Institute of Agri- cultural Engineering and Land Improvement of the Martin-Luther Uni- versity Halle-Wittenberg in order to extend automatic tractor steering which had been developed as of the beginning of the nineties to comprise safety-relevant tasks. The goal of the first development step is the timely recognition of given field boundaries, natural obstacles, and freely chosen blocked areas, which are noticed in time during the field ride due to the combination of automatic steering with a Differential Global Positioning System (DGPS) and can warn the driver by triggering optical and/or acoustic signals before a critical position is reached. The intended hard- and software-based connection of these two different technical systems in a „safety system for agricultural machinery“, which has a modular design and works independently of the driver, is to make a contribution towards improved ergonomic process design and to create the necessary prerequisites for greater process security.
The Modelling of Odour Dispersion with Time-Resolved Models
(2000) Boeker, Peter; Wallenfang, Oliver; Koster, Frank; Croce, Roberto; Diekmann, Bernd; Griebel, Michael; Schulze Lammers, Peter
In connection with the methods used so far, this contribution describes a new approach for the modelling of odour dispersion. Using the aid of example cases, the methodology of odour prognosis with different approaches is explained, and their advantages and dis- advantages as well as their limitations are discussed. Particular attention is given to close-range dispersion from odour emis- sion sources with low source heights and a complex fluidic environment. Typical examples of such cases are agricultural sources or biological processing plants (composting, sewage treatment plants). The new dispersion model is a further development of the NaSt3D model with two variants of improved dispersion modelling, an advection- diffusion approach (Euler model) and a Lagrange-particle model. This model is able to conduct time-resolved calculations of flows and disper- sion and hence allows the question of concentration fluctuation, which is important for odour phenomena, to be integrated into the model. The parallelizing of the computer code enables terrain- and source configu- rations which have been too complex thus far to be calculated in a fine division of the calculation grid. At present, computer clusters and high- performance computers can be used for this purpose in anticipation of the fast further development of efficient personal computers. The consistently analytical approach avoids empirical model supple- ments with adaptation parameters, such as the otherwise necessary mo- dels of exceeding probability, and can thus be calibrated on a physical basis.
Monitoring Odour Emissions from Agriculture - Use of Chemical Sensor Arrays
(2000) Maier, Barbara; Riess, Gisbert; Zeisig, Hans-Dieter; Gronauer, Andreas
For a wide variety of reasons, odour is causing more and more problems because it disturbs residents who live close to farms. Due to the growing sensitivity of the population, the measurement of undesirable odours has become a problem that may no longer be neglected. In this contribution, results of a comparison of different ventilation sy- stems gained with a multisensor array are documented. The big advan- tage of multisensor array measurements over olfactometry lies in the continuous registration of measurement values in contrast to the few random samples taken during olfactometric measurements.
Solar Drinking Water Supply on the Pasture
(2000) Scholz, Volkhard; Daries, Werner
Agriculture opens up various possibilities for the use of photovoltaic sy- stems, especially for the supply of water to plants and animals at loca- tions which are far from the mains. Practical examinations lasting se- veral years show that photovoltaic pump systems on pastures remote from the mains can guarantee the supply of water to cattle reliably and even economically. However, this requires that the performance para- meters of the pump and the water consumption of the animals are known and well coordinated, i.e. that the system is optimally dimensioned. In the following contribution, the results of several years of pump tests and measurements of the water consumption of grazing cattle are pre- sented, and conclusions with regard to the dimensioning of photovoltaic pasture drinkers are drawn. Under the climatic conditions in Central Europe, an installed power of only 1 to 2 watts per head of non-lactating cattle and per metre of height difference is required during the summer months. Furthermore, operational experiences and costs of PV drinkers for cattle used in practice are reported on. Optimally dimensioned PV pasture drinkers can supply drinking water at less than a quarter of the expense caused by conventional drinking water systems.
Heated Drinking Water for Dairy Cows?
(2000) Beck, Jürgen; Katzschke, Daniela; Steingaß, Herbert
Recently, dairy farmers and manufacturers repeatedly claimed that hea- ted drinking water could improve feed intake, milk yield, and animal health, especially in high yielding dairy cows. This was the reason for an examination (4 trial periods) which was carried out at the Experimental Station for Livestock Biology and Ecological Farming of the University of Hohenheim. The influence of heated drinking water (24°C, 17°C, 24°C) was compared with the effect of cold water with a constant tempe- rature of 3°C using feed- and water intake, milk yield, milk constituents, and drinking behaviour as examination parameters. The trials yielded the following results: - daily intake of roughage and concentrate feed - not influenced; - daily water intake - significant influence in some cases (more cold water was drunk); - total daily drinking duration - significantly longer for cold water, slower intake; - daily milk yield (FPCM) - insignificant tendency towards higher milk yield with cold water; - milk fat content - insignificant tendency towards higher values with cold water; - live body mass - not influenced; - selection trial: 94.4% of the daily water intake in the form of warm water - reduced excess heat of the high yielding dairy cow with cold water. Therefore, heating the drinking water for dairy cows to 17°C or 24°C in order to increase the milk yield does not make sense. Furthermore, hea- ting to 24°C must be expected to require a converted 2.4 kWh/cow*day. This corresponds to daily electricity costs of approximately DM 0.54/cow*day, which could be compensated for through a yield increase of about one litre per day, which, however, was impossible to realize. If the only goal is to guarantee frost-free water supply, more cost-efficient solutions certainly offer themselves.
Methane (CH4) and Nitrous Oxide (N2O) Emissions from Animal Husbandry
(2000) Hartung, Eberhard; Monteny, Gert-Jan
The greenhouse gases methane (CH 4 ) and nitrous oxide (N 2 O) contribute to global warming. N2 O also affects the ozone layer. The most important sources of greenhouse gas emissions in agricultural animal husbandry are the animals, animal houses (indoor storage of animal excreta), the outside storage of manure and slurry and their treatment (e.g. compost- ing), as well as the spreading of manure and chemical fertilizers. The source of methane emissions from animal husbandry is largely endoge- nous. Nitrous oxide, however, is mainly produced and emitted during the storage and treatment of animal excreta, as well as after spreading. Although in many countries emphasis is already being placed on the re- duction of environmental pollution caused by nutrients, ammonia emis- sion and odour nuisance, the reduction of the emission of greenhouse gases will become equally important in the near future to meet inte- grated sustainability criteria (Kyoto agreement). While ammonia- and odour emissions affect farmers directly, it is currently not absolutely neces- sary to reduce greenhouse gas emissions because no laws governing this field have been enacted yet. As compared with ammonia emission, only a few data regarding the emission of CH4 and N2O from animal husbandry are available in the literature. In addition, these values can be used only to a very limited extent. The literature summarized below shows that reliable data regarding CH4 emissions are more or less available only for animal housing systems. There are virtually no data for N2O, mainly because the measurement of N2O concentrations sometimes causes considerable diffi- culties (detection limits of continuously working measuring instruments, e.g. IR spectrometer). There is a large variation in the emissions rates stated in the literature, which must mainly be attributed to the large number of parameters (e.g. temperature, substrate) that determine the emission of greenhouse gases. For this reason, some normative values, e.g. those used in national and international emission budget calculation, may have to be revised fre- quently based on the outcome of experimental research. As knowledge about source-specific emission rates grows, there is an increasing need for a more detailed description of the emission factors used in national emission budget calculations and of the parameters which influence them.
Measuring Techniques for the Assessment of the Trafficability of Fen Grasslands
(2000) Tölle, Rainer; Prochnow, Annette; Kraschinski, Sven
Fen grasslands belong to the vertically layered soils with a strong and very variable top layer, the gras sod, on a weak soil base, the peat. Mea- suring techniques for trafficability assessment must reflect the site- specific load-bearing capacity of the ground with sufficient accuracy and show a close relation to permissible mechanical load-input by machine- ry. Furthermore, they must be applicable with tolerable expenditure. In this paper, examinations with a penetrometer, a plate test device, and a shear vane are presented. The cone index only allows for insufficient estimation of the impact of vegetation on the load-bearing capacity. The- re is only a very loose correlation between the values of mechanical load-input by vehicle variants and the necessary cone index. On fen grassland, the load-penetration curves obtained with a plate test device exhibit a typical course with a more or less distinct pressure maximum. Its correlations to soil moisture content and vegetation in principle allow this measuring technique to be used for the assessment of the load- bearing capacity. This also applies to the prediction of the permissible load-input during the passage of vehicles. However, since a large amount of data is necessary, the expenditures required for plate tests are too high. The shearing vane enables the load-bearing capacity of the the ground and the permissible load-input to be established with sufficient precision. It is therefore an appropriate measuring technique for the as- sessment of the trafficability of fen grasslands on the basis of empirical relations.
Determination of Soil-Related Trace Gas Fluxes during the Cultivation of Renewable Raw Materials
(2000) Hellebrand, Hans Jürgen; Scholz, Volkhard
The emission of climate- and environmentally relevant trace gases af- fects the environmental balance of renewable raw materials. Depending on the intensity and the kind of nitrogen fertilizing, additional nitrous oxide or ammonia is emitted, and methane degradation in the soil is in- fluenced. These trace gas fluxes are measured using the flux chamber method in connection with gas chromatography (GC) and Fourier- transform infrared spectroscopy (FT-IR). The GC technology provides the advantage of higher accuracy for some selected trace gases. The FT- IR measurements show that the release of ammonia caused by fertilizing with calcium ammonium nitrate is below the detection limit. The nitrous oxide emission factor measured at a loamy-sandy location is based on GC results. The average quantity of all fertilizer-induced N2 O-N emis- sions only amounts to approximately 0.2 % of the annual quantity of N- fertilizer applied. In addition, the GC measurements show that the de- gradation of atmospheric methane in the soil depends on the soil tem- perature. The mean annual value of methane degradation at the exam- ined location amounts to 0.7 kg CH4 ha-1 a -1.
Emissions Caused by Manure Composting
(2000) Hellebrand, Hans Jürgen; Kalk, Wolf-Dieter
The evaluation of the nitrogen balance of biological farming included the measurement of gaseous emissions during manure composting under practical conditions. The results show that ammonia- and methane emis- sions subside within three to four weeks. Nitrous oxide emissions exhi- bited significantly greater variability with regard to time and place. Ma- xima of nitrous oxide emission were observed mainly after ammonia and methane had decayed. The mean total flux per compost period amounted to 1,322 g m-2 of methane, 76.9 g m-2 of ammonia, and 19.8 g m-2 of ni- trous oxide. The relation of these average values to the mean flux of car- bon dioxide per composting period was 4.6 10-2 for CH4 , 2.7 10-3 for NH3 , and 6.9 10-4 for N 2 O. Both the total average gas flux and the mean ratio of total gas emissions can serve to quantify the impact on the envi- ronment. The average gaseous nitrogen losses measured during manure composting amounted to 6% of the initial nitrogen content. Carbon los- ses account for 35% of the initial carbon content.
Biofilters - The Influence of Different Filter Materials on the Reduction Efficiency
(2000) Martinec, Milos; Hartung, Eberhard; Jungbluth, Thomas
The influence of five different filter materials on the reduction efficiency of biofilters has been investigated in parallel long-term measurements in a stall for fattening pigs. The greatest odour reduction (approximately 81%) was achieved with biochips and a mixture of coconut fibre and fi- bre peat as filter materials. All filter materials additionally reduce am- monia emissions by an average of about 9 - 30%. Biofilters with bio- chips caused considerably lower flow resistance and electricity con- sumption than filters with other materials. Biofilters allow odour emissions from farm animal husbandry to be re- duced by approximately 25 - 95%. Ammonia emissions also diminish to a certain extent (about 0 - 35%). However, very high operating expenses are attached to the use of biofilters if they are used properly (HARTUNG et al., 1997; HOPP, 1998; MANNEBECK, 1994). For this reason, they are used only when the minimum distance required by the VDI 3471 (1986) and VDI 3472 (1986) guidelines as well as the TA Luft (1986) (German Air Pollution Regulations) cannot be kept. The selection of the filter material provides a significant possibility to further optimize bio- filters.The present study was conducted to establish the odour reduction achieved by selected filter materials. Additionally, it was the goal of this research to examine the influence of the filter material on the reduction of the emission of NH3 , CO2 , CH4 , and N 2 O, as well as flow resistance and electricity consumption.
Recognition and Valuation of Odour Emissions from Agriculture - Use of Chemical Sensor Arrays
(2000) Maier, Barbara; Riess, Gisbert; Gronauer, Andreas
For a wide variety of reasons, odour is causing more and more problems because it disturbs residents who live close to farms. Thus far, an as- sessment of this annoyance has only been possible with the help of the human nose. Since this olfactometric method has many shortcomings such as lack of reproducibility, subjectivity, high personnel costs, and dependence upon the daily form of the test persons, a system is being de- veloped that will allow odour to be measured with an instrument. In this article, qualitative results are documented which prove the suita- bility of the systems used.
Decomposition of Growth from Grassland after Mulching
(2000) Prochnow, Annette; Kleinke, Matthias; Streßmann, Uwe
When mulching on grassland or fallow arable land, the vegetation is cut, chopped, and spread in a wide swath in one work step. The material re- mains on the field, where it decomposes. Mulching is a simple, inexpen- sive method and, if applied properly, it is a suitable cultivation measure for many grassland locations and fallow arable land. A decisive factor for successful mulching is the rapid decomposition of the mulched mate- rial because long covering and shading of the grass sod leads to undesi- rable changes in the vegetation. Extensive field trials regarding the de- composition of mulched material served to determine suitable periods for the mulching of typical grassland sites. The results show that the de- composition of mulched material mainly depends on the weather condi- tions, while the type of vegetation and the intensity of chopping are of lesser importance. The modelling of the decomposition of mulched mate- rial allows the remaining mass per area unit to be calculated from the initial mass per area unit, the sum of temperature, and the sum of preci- pitation during the period after mulching. Based on simulation with weather data of a reference region collected over many years, it is pos- sible to estimate the duration of decomposition for varying growth ma- sses and mulching periods. From this, favourable, site-specific periods for the mulching of grassland biotopes are derived. The first grassland growth can be mulched until the end of July/beginning of August, the se- cond growth until the end of September/beginning of October.
Modelling the Shock Behaviour of Potatoes
(2000) Winkelmann, Jörg; Fürll, Christian; Schlottmann, Günther
In the Federal Republic of Germany, approximately 9 million tonnes of potatoes are harvested every year. On its way between the harvest and consumption, the potato passes through a long transport chain and se- veral processing steps. The most prominent feature of this process is that the potato sustains mechanical shocks. Even though shocks are always damaging to the tissue of the potato, they must be accepted as part of some procedures such as sorting or mechanical peeling in order to reali- ze functional principles. However, the current state of the art also en- ables and requires processes to be considered under the aspect of gentle potato treatment. Given these considerations, the simulation of the shock behaviour plays a central role. Studies on mechanical peeling with a spatially swinging plane peeler provide a calculation approach for the simulation of the shock behaviour of potato tubers.
Clamping Systems and Ratio Control of Belt - or Chain CVTs
(2000) Westenthanner, Ulrich
This paper deals with new concepts for the hydraulic clamping system of continuously variable metal-chain or metal-belt drives (CVT) to improve and enlarge the basic functions and to reduce energy consumption. In addition, sufficient clamping forces must be guaranteed for the tough demands in tractors. Starting with a comparison of two actual control systems (for clamping forces and transmission ratio) which are designed for use in vehicles, an improved constant-flow clamping system is pre- sented. It meets the demands of agricultural tractors, i.e. this constant- flow system includes a ratio-shifting mode during standstill of the drive- line. Afterwards, measurement results for a new energy-saving hydraulic clamping system with pressure control are reported. It retains significant advantages of the constant-flow system. For use in tractors, it is very important to maintain immediate response of the clamping pressures even if torque increase is very high. This goal has been reached by sub- stantially redesigned torque sensors. Simulation calculations confirm the energy-saving potential and provide fundamentals for the development of the control strategies.
Use of Chemical Sensor Arrays for the Recognition and Valuation of Odour Emissions from Agriculture
(2000) Maier, Barbara; Riess, Gisbert; Gronauer, Andreas
For a wide variety of reasons, residents who live close to farms are claiming more and more that they are disturbed by odour emissions. Thus far, the human nose has been the only means of assessing the an- noyance caused by these emissions. Since this olfactometric method has many disadvantages such as lack of reproducibility, subjectiveness, high personnel expenses, and its dependence upon the daily form of the test persons, a system is being developed which allows odour to be measured by an instrument. This contribution presents the methods and documents initial quantitati- ve results which prove the suitability of the systems used.
Comparison of Process Chains for the Supply of Bio-Fuels
(2000) Brökeland, Ruth
When planning projects for the energetic utilization of biomass, invest- ment costs as well as expenses for the processing and supply of bio-fuels must be precisely determined. The calculation of realistic prices for bio- fuels requires the consideration of complete engineering process chains, which include all work steps from the cultivation of the vegetable bio- mass to the spreading or disposal of the ashes. In feasibility studies, of- ten only simplified machinery chains or global values are considered. When the planning program HORTEB was developed, data for numerous work steps were collected and used for a comparison of different simpli- fied and complete process chains.

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