Laboratory Construction for Biogas Production from Plants

Transcription

1 ORIGINAL Expert paper SCIENTIFIC PAPER Bogomir MURSEC, Peter VINDIS Laboratory Construction for Biogas Production from Plants Bogomir MURSEC, Peter VINDIS Univerza v Mariboru, Fakulteta za kmetijstvo, Vrbanska 30, 2000 Maribor, Slovenia ( bogomir.mursec@uni-mb.si Abstract The aim of the paper is to present the construction of a mini digester for biogas production from plants in laboratory. With the mini digester the amount of biogas production (methane) from different silage plants is observed. The basic structure of the mini digester is from nonrust steel, on which other components are fixed. The most important are eudiometers, pump and boiler with thermostat, fermenters, thermometer and barometer. The mini digester is built from twelve units. Each unit is built from a fermenter with substrate and a eudiometer with outside bowl. The amount of biogas is measured on the gas tube of eudiometer. The composition of produced biogas is determined with a gas analyser. Key words: biogas production, mini digester, eudiometer, fermenter Introduction The biogas is a renewable source of energy. It is produced and used in a decentralized way, therefore it increases the reliability of power supply. With proper technology of separation of CO 2 and other gases from the biogas a fuel can be obtained that is quite equivalent to natural gas, but it is its advantage that it does not cause additional emission of greenhouse gases ( After accession of Slovenia to the EU the interest in the use of the biogas as a source of energy has increased. This is particularly due to the fact that there are no longer any restrictions on the import of technology, equipment and materials from the countries members of the EU and that the type and extent of substrates for the anaerobic digestion process are on the increase. On the one hand, there are no more any customs walls for the purchase of proper technology and the sanitary regulations do no more allow the hitherto disposal of a series of organic wastes; on the other hand, the legally ensured buying and favourable buying tariff rates for electric energy based on biogas in Slovenia assure a stable economic frame for investments into this promising prospect of producing energy through processing of biologically decomposable and energy-rich wastes. Also numerous EU programmes encourage the transfer of know-how and cooperation in the area of the technological development, the use of renewable sources of energy and the regional development. Considering also the rising prices of fossile fuels, particularly, oil and increasingly evident signs of global atmosphere warming, it is not surprising that in Slovenia, too, there is an increased interest in resources and technologies which allow production of electric and thermal energy not causing climatic changes and which, in the same time, ensure efficient disposal of a great part of biologically decomposable wastes and production of high-quality manure more friendly to plants, underground water and, last but not least, less inconvenient for people s noses (Fredriksson et al. 2006). Material and methods The gas apparatus, used for laboratory tests, comprises twelve gas cells. Each cell consists of a reaction vessel (500 ml fermenter) and a well closed gas pipe. The gas pipe - eudiometer contains the closing liquid and is of 350 ml size. It is connected to the outside bowl with solution. The bio gas produced in fermenters supplants the closing liquid in the gas pipe into the outside levelling bottle of 750 ml volume. The gas produced is read on the gas pipe. The fermenters are submerged into water with constant temperature 35+/-1 degree C and Proceedings. 43 rd Croatian and 3 rd International Symposium on Agriculture. Opatija. Croatia ( ) XXX) 548

2 Laboratory Construction for Biogas Production from Plants are connected with the glass gas pipe (DIN , 1985). The biogas produced contains 50-75% of methane, 10-40% of carbon dioxide and other matters (H 2, H 2 S, N 2, NH 4,...). The exact composition is determined by the gas detector (Amon et al. 2007). Figure 1 shows the entire structure for biogas production for laboratory purposes. Picture 1. Laboratory construction of mini digester for biogas production in working The basic structure of the mini digester is made of stainless steel (inox). It is 2500 mm long, 1000 mm high and 350 mm wide. At the top a shelf is provided on which there are the levelling bottles for surplus closing liquid. At the bottom, a trough 200 x 200 mm lined with stiropor is provided to prevent excessive heat losses and to enable the fermenters to be in the dark. In the trough a heating pump, ensuring constant temperature and water circulation, is placed beside the eudiometers. Thus, as uniform water temperature as possible is reached over the entire trough. The eudiometers are fixed to a metal beam above the structure, so that they can not overturn and that they can be removed and fixed as easily as possible for test purposes. A thermometer and a barometer measuring, through a sensor, the water temperature in the trough and separately the adjacent air temperature are fixed on the left side of the steel structure. Results and discussion The mini digester serves to produce the biogas from various energy plants and other organic waste material. It consists of twelve units so that three tests with three repetitions simultaneously are possible, whereas three units serve for the control. During the test the biogas production must be read daily. The volume developed is let out in case of each reading, each day at the beginning of test, later on every two or three days, when the gas formation diminishes. The gas composition is measured by gas detector Geotechnical Instruments GA 45. The principal component on the laboratory device for biogas production is the eudiometer. The eudiometer is a gas pipe with scale, closed on one side. It consists of two parts in such a way that the top glass pipe is directly connected to the bottle with fermenter, which significantly facilitates the work, since no pipes, separately connecting the fermenter bottle and the fermenter, are necessary. Figure 2 shows one gas cell - eudiometer with the fermenter in water bath. The eudiometer holder (clamp) was fixed to the middle cross piece of the structure and, thus, the eudiometer stability was significantly improved. The clamps are lined with cork to reduce damages to glass. Field Crop Production 549

3 Bogomir MURSEC, Peter VINDIS Picture 2. Eudiometer with the fermenter in water bath The levelling bottles (figure 3) have 750 ml volume and are placed onto the shelf at the top of the entire structure. The levelling bottle contains the closing liquid serving for the liquid supplanted by the gas. They are connected to the eudiometer through a rubber hose. The closing liquid consist of sulphuric acid added to distilled water; Na 2 SO 4 10 H 2 O are added to that mixture through slight heating. A few drops of methyl orange solution are added to that solution. Picture 3. The levelling bottle with the closing liquid 550

4 Laboratory Construction for Biogas Production from Plants The fermenter has 500 ml volume and is filled with substrate up to 3/4 of volume. Silages of various energy plants are used as substrate. The substrate is mixed with cleavage sludge containing methanogen bacteria in a certain ratio, which are necessary for the fermentation process. The fermenter is located in the dark in the water bath with constant temperature 35 +/- 1 degree C. Constant temperature is maintained by the heating pump (Figure 4) simultaneously mixing the water in the trough. Due to the trough length the placing of the heating pump is of particular importance. It is ideal to place it in the middle of the trough, where the outlet opening of the pump is divided into two parts by a Y distributor. Both parts are placed at opposite ends of the trough, which additionally accelerates mixing of water, since the heated water on the sides pushes the water towards the middle of the through, consequently, towards the pump. Thus, very good water circulation over the trough and optimum water bath temperature are reached as a condition for optimum fermentation process. Picture 4. Heating pump in the water-bath Through thermometer the water temperature in the trough is accompanied and suitably adjusted through the heating pump. Thus, ideal conditions for fermentation are reached. The thermometer measures also the ambient temperature. Also the environment pressure must be measured. The ambient temperature and pressure serve for later correction of results. The gas composition is measured by the gas detector Geotechnical Instruments GA 45. Figure 5 shows the gas detector GA 45. Field Crop Production 551

5 Bogomir MURSEC, Peter VINDIS Picture 5. Gas detector GA 45 Conclusions The aim of the paper is building of the mini digester for biogas production from energy-rich plants. The mini digester serves for the tests of biogas production from energy rich plants (maize, sorghum, amaranth) in laboratory. The basic structure is of welded construction from stainless steel (inox). The mini digester consists of twelve units so that four tests simultaneously with three repetitions can be performed. So, the resulting data are accurate and diverse. Each unit consist of an eudiometer, fermenter containing the substrate and a levelling bottle for surplus closing liquid. Other components ensuring correct functioning of the mini digester are the pump and heater with thermostat, the thermometer, barometer, eudiometer clamps and rubber hoses connecting individual components. The final analysis of the produced biogas is effected by the gas detector GA 45. References Amon T., Amon B., Kryvoruchko V., Zollitsch W., Mayer K., Gruber L. (2007). Biogas production from maize and dairy cattle manure Influence of biomass composition on the methane yield. Agriculture, Ecosystems and Environment. Volume 118: DIN , Determination of digestion behavior sludge and sediments. Beuth Verlag, Berlin. Fredriksson H., Baky A., Bernesson S., Nordberg Å., Norén O., Hansson P (2006). Use of onfarm produced biofuels on organic farms Evaluation of energy balances and environmental loads for three possible fuels. Agricultural Systems. Volume 89: sa2008_