ECONOMIC EXAMINATION OF BIOGAS GAINED FROM MUNICIPAL WASTE KOMMUNÁLIS HULLADÉKBÓL NYERT BIOGÁZ FELHASZNÁLÁSÁNAK GAZDASÁGI VIZSGÁLATA *Tamás MOLNÁR, **László SALLAI, ***Dezső FODOR *University of Szeged College of Agriculture, Szeged, Hungary **ASA. Ltd. Hódmezővásárhely, Hungary Abstract: The refuse dump of Hódmezővásárhely will provide up-to-date storage and neutralisation for the refuse of the town for 50 years. The storage of the refuse takes place in waste dump by adequate compression. During the storage gases, mainly methane and carbon dioxide are developed due to the biological decomposition. We must prevent these gases to get into the atmosphere as they are involved in the global warming of the Earth and so they may cause changes in the environment. With the regulations getting stricter in the EU where we are going to be members soon it is essential that a refuse dump should have a biogas deflector system in order to protect our environment. A compressor drains gases from the waste material, while another compressor is used for taking the gases to the place where they are used. From utilisation point of view a considerable quantity is developed, which can be diversely utilised.
Összefoglaló: A hódmezővásárhelyi kommunális hulladéklerakó telep biztosítja Hódmezővásárhely hulladékának korszerű és környezetbarát ártalmatlanítását, ötven évig. A kommunális hulladékok tárolása depóinában történik megfelelő tömörítéssel. A tárolás során a biológiai bomlásból eredően gázok képződnek, főleg metán és széndioxid. Ezeknek, a gázoknak a légkörbe kerülését meg kell akadályozni, mivel a föld globális felmelegedéséhez vezetnek, ezzel a környezeti változásokat okoznak. A környezetvédelmi szabályok szigorodásával és Európai Uniós tagságunkból eredően, egy hulladéklerakó telepnek rendelkezni-e kell biogáz elvezető rendszerrel, a környezetünk megóvása érdekében. A hulladékból a gázoknak az elvezetése elszívással történik egy kompresszor segítségével és egy másik kompresszor, pedig a hasznosítás helyére szállítja. Hasznosítás szempontjából jelentős mennyiség keletkezik, ezeknek a felhasználása sokrétű.
Keywords: refuse dump, biogas, renewable energy, regulations getting Kulcsszavak: kommunális hulladéklerakó-telep, biogáz, megújuló energia, környezetvédelmi szabályok
INTRODUCTION The A·S·A· Hódmezővásárhely refuse Ltd. Collect the refuse in Hódmezővásárhely and environs and store them in deponia. The refuse dump of Hódmezővásárhely was built on the basis of the regulation of environmental protection. The refuse dump can store 3.9 million m3 refuse that is able to provide environment friendly placing for the refuse of Hódmezővásárhely and its environs for 50 years. The laid refuse on deponia go through disintegration process therefore deponia-gas of high energy content originate from refuse. The quantity of gas depends on the composition of refuse, the technology of the deponation and passed time from the putting down. The deponia gas consists of mainly methane and carbon-dioxide. When deponia gas flows out it has a harmful effect on the environment and it causes greenhouse effect, it exudes unpleasant smell and it can create exploding gas mixture. We can establish environment friendly conditions with the suitable and checked extraction and utilization of the deponiagas.
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MATERAL AND METHOD The Hódmezővásárhely refuse Ltd.’s communal solid refuse unloading place works in the outskirts of Hódmezővásárhely on the area No. 01957/1 (Figure 1). The Bekefi homestead 1100 m is situated the nearest to the refuse unloading place. The nearest dwelling house is far away (2500m). The refuse dump of Hódmezővásárhely is situated 20 ha and the top height of deponia is 30m.
Figure 1 The drawing of the refuse works
1 The elements of deponia gas extracting system (Figure 2) Gas wellGas collecting pipesGas controller unitCompressor unitTorch
Figure 2 Process figure of gas production [2]
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2. The examined parameters during gas production
Figure 3 The examined parameters during gas production
The biogas production as biotechnology process claims exact regulation. The regulation of process is a difficult task as the composition of the basic materials move on a rather wide scale. Therefore handling the process is often confined to only controlling a few parameters, and consequently the parameters of the result cannot be defined punctually. The regulation of process can be controlled with a computer which increases our expense. The biogas production as gas technology has the danger of explosion and fire. In the process of the biogas production the fire-and explosion protection have to be made certain that the gas can’t cause any problems neither getting out of the system nor in the system. MEASURING AND RESULTS 1. Measuring: 2005. March- October [307 day] The measuring was aimed at the examination of the quality and quantity of the originating biogas and refuse. In the second step 40.000t communal refuse + 10.000t oleaginous refuse was placed. The placement of the oleaginous refuse was important that we could increase the quantity of the originating biogas and the methane content of the gas. The time of the measuring: 2005. March-October - methane 60 % - carbon-dioxide 29.2 % - oxygen 2.6 % - nitrogen 8.2 %
On the basis of the mesured data the biogas: - 40 Nm3/hour - 960 Nm3/day - 300.000 Nm3/year
Figure 4 Biogas composition
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CONCLUSIONS On the refuse dump of Hódmezővásárhely originating biogas can be recycled for energy production and heat production. 1 The recycling of the electrical energy The originating biogas in the refuse dump of Hódmezővásárhely is burnt up in gas engine. Because of this heat energy and electric energy originate. We have to choose whether we will produce as much power as we can use for our own aim or we will produce as much as we can do and we can install the plus power into the electrical system. The islands works have some advantages that we are independent of the national electric power system. The operation isn’t influenced by either a rise in prices or quantity regulations. In case of parallel works we can produce as much power as the biogas can make possible and we can sell the surplus for the energy service. The surplus electric power: We can use this for the public lighting on the works or building electrical aim as interior use. Local electric service called DEMÁSZ Ltd. has to buy the energy power which we can’t use inside the works.
Figure 5 The production of the electric power
2 Heat energy recycling (Figure 6) The buildings can be heated in winter and it can supply hot water The buildings’ water supply 2.1 We have to take these into consideration at calculation of quantity of annual fuel On the basis of meteorological statistics of the annual heating hours (4200 h/year) The rate of heating hours per day 60 % The number of hour of heating: 4320 h On 100 % (-15 C at outside temperature) 20h On 80 % (-6 C at outside temperature) 186h On 60 % (+1 C at outside temperature ) 1215h On 40 % (+120 C at outside temperature) 2899 h. The need of heat of building per year: 20 h 39.26 MJ/h = 785,304 MJ 142
186 h 39.26 MJ/h = 7,302.36 MJ 1,215 h 39.26 MJ/h = 47,700.9 MJ 2,899 h 39.26 MJ/h = 11,384.74 MJ The need of heat per year: Q = 169,601.74 MJ/year The efficiency of the placed boiler in the building is 85%.
Figure 6. GB Ganz boiler.
Thermal value of biogas: Hbiogas = 5.5 – 6.5 kWh/Nm3 Hbiogas = 23.4 MJ/Nm3 The quantity of burnt fuel at 85 % efficiency
m
Q 169601,74 MJ/year 8526,9854 m3/year 3 η H 0,85 23,4 MJ/m k biogas
Thermal value of natural gas:
7,5 7,8k Wh/Nm3
H naturalgas
Hnaturalgas = 28.08 MJ/Nm3 The quantity of burnt fuel at 85 % efficiency Q 169601,74 MJ/year m 7105,8211m3/year η H 0,85 28,08 MJ/year k naturalgas The expense of natural gas per year: 1Nm3 expense of natural gas: 55 Ft K = 7,105.8211 m3/year 55 Ft = 390,820 Ft The heating of the building cost 390,820 Ft per year and the hot-water system is as an additional expense. On the basis of the data of operation the annual cost of the social building is 1 million HUF, but if we solve it with biogas technology, the annual expense won’t appear only the operation expense of the biogas set will appear. If we used the biogas for only the heating system, the rather high cost of investment (40 million HUF) couldn’t be returned only in case of complete biogas utilisation.
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REFERENCES A.S.A. Hódmezővásárhely Köztisztasági Kft.: A hódmezővásárhelyi hulladéklerakó telep környezeti hatástanulmánya. Hódmezővásárhely, 2000
A.S.A. Hódmezővásárhely Köztisztasági Kft.: Maroslelei úti hulladékdeponáló és kezelő létesítmények üzemeltetési utasítása. Hódmezővásárhely, 1995
BARÓTFI, I.: Környezettechnika kézikönyv. Mezőgazda Kiadó, Budapest: 2000
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