History and status to date in Europe
Very old sources indicate that using wastewater and so-called renewable resources for the energy supply is not new, but was already known before the birth of Christ.
Even around 3000 BC the Sumerians practiced the anaerobic cleansing of waste.
The Roman scholar Pliny described around 50 BC some glimmering lights appearing underneath the surface of swamps.
In 1776 Alessandro Volta personally collected gas from the Lake Como to examine it. His findings showed that the formation of the gas depends on a fermentation process and that the gas may form an explosive mixture with air.
The English physicist Faraday also performed some experiments with marsh gas and identified hydrocarbon as part of the it. A little later, around the year 1800, Dalton, Henry, and Davy first described the chemical structure of methane. The final chemical structure of methane (CH4), however, was first elucilated by Avogadro in 1821.
In the second half of the 1941 century, more systematic and scientific in-depth research was started in France to better understand the process of anaerobic fermentation. The objective was simply to suppress the bad odor released by wastewater pools. During their investigations, researchers detected some of the microorganisms which today are known to be essential for the fermentation process. It was Bechamp who identified in 1868 that a mixed population of microorganisms is required to convert ethanol into methane, since several end products were formed during the fermentation process, depending on the substrate.
In 1876, Herter reported that acetate, found in wastewater, stoichiometrically forms methane and carbon dioxid in equal amounts. Louis Pasteur tried in 1884 to produce biogas from horse dung collected from Paris roads. Together with his student Gavon he managed to produce 100 L methane from 1 m3 dung fermented at 35 °C. Pasteur claimed that this production rate should be sufficient to cover the energy requirements for the street lighting of Paris. The application of energy from renewable resources started from that time on.
Biogas from Waste and Renewable Resources. An Introduction. Dieter Deublein and Angelika Steinhauser
Copyright © 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 978-3-527-31841-4
200 180 160
□ Straw and agricultural by-products Oenergy crops
Figure 3.1 Biogas production across European countries. 3.1
First attempts at using biogas
□ Straw and agricultural by-products Oenergy crops
Figure 3.1 Biogas production across European countries. 3.1
First attempts at using biogas
While Pasteur produced energy from horse dung, in 1897 the street lamps of Exeter started running on gas from waste water. This development suggested that more and more biogas could be produced by anaerobic purification plants for wastewater. Most of the biogas, however, was still wasted to the atmosphere.
In 1904 Travis tried to implement a two-step process which combined the purification of waste water with the production of methane.
In 1906 Sohngen accumulated acetate in a two- step process. He found that methane was formed from three basic materials: formate plus hydrogen plus carbon dioxide.
In 1906 the technician Imhoff started constructing anaerobic waste water treatment units in the Ruhr, Germany. He installed so-called "Imhoff tank" (Figure 3.2) with separate spaces for sedimentation and digestion. The residence time of the bio waste was 60 days.
In Germany methane gas was first sold to the public gas works in the year 1923.41) In the next years this practise became more and more common in Europe. A further development was the installation of a CHP near the biogas production and to produce the current necessary for the waste water treatment plant and to heat houses with the excess heat from the CHP.
Until the 2nd world war, the use of biogas was progressing very fast and much effort went into developing more efficient systems, e.g., floating-bell gasholders, efficient mixers, and heating systems to increase the yield of digestion. In Europe, highly technical spherical digestors agitated with intermittent vertical screw
Figure 3.2 Imhoff tank - a sedimentation tank for the mechanical sewage treatment.
conveyors and a haul-off in the cover was preferred. In the United States, simple cylindrical vessels were used with flat bottoms, continuously circulating mixing systems, and collecting pipes at the top.
Around 1930 it was first tried to remove water, carbon dioxide, and sulfide from the biogas, to compress it in gas bottles, and to use it as fuel for automobiles. In order to maximize the efficiency of such a procedure, so-called co-fermenters, i.e. solid organic waste, e.g., food, cereals, and silage were added. Different combinations were tried, but only in 1949 (Stuttgart) the addition of fat after fat separation enabled the yield of biogas to be increased.
In Halle, experiments on digestion were performed by adding waste liquorice, rumen, lignin and/or cereals. Lignin was the least efficient material, providing 19 L gas per kg dry matter with a dwell period of only 20 days. Rumen provided 158 L kg-1, liquorice even 365 Lkg-1 butwith a dwell period of45 days. Around 1950 Poebel conducted some extensive research on co-fermentation in the Netherlands by including organic waste of households in his experiments.
Around the same time (1930-1940) the idea came up to use agricultural waste to produce biogas. Buswell ' s target was to provide the whole amount of gas consumed by Urbana, a small city in Illinois. He examined many different natural materials. In parallel, Ducellier and Isman started building simple biogas machines in Algeria to supply small farmhouses with energy. This idea was brought to France, and many people installed their own small and technically very simple biogas plants.
Around 1945, only Germany started using agricultural products to produce biogas. Imhoff again was leading. In 1947 he claimed that the excrement of one cow delivered 100 times more biogas than the sewage sludge of one single urban inhabitant. He projected how much biogas the excrement of cows, horses, pigs, and potato haulms would supply. The first small biogas plant with a horizontal cylindrical vessel for fermentation was developed in Darmstadt, and in 1950 the first larger biogas plant was inaugurated in Celle. In total, about 50 plants were installed during the following years in Germany.
While expanding the number of biogas plants, globally researchers deepened their knowledge about the chemical and microbial processes contributing to fermentation. Doing very fundamental biochemical research in 1950, Barker detected the methane-forming bacteria Methanosarcina and Formicicum methanobacterium. Very important also was the finding from Bryant et al. in 1967 showing that methane -forming microbial cultures consisted of a minimum of two kinds of bacteria. One type was said to be responsible for converting ethanol to acetate and hydrogen, and the other for forming methane via chemical reaction of carbon dioxide and the free hydrogen. Today it is known that four specific and different kinds of bacteria must work in synergy to produce biogas.
Around 1955 the importance of biogas was significantly reduced, as biogas was not profitable any longer due to an excess of oil. The price of fuel oil was very low, ca. 0.10 L-1- At the same time, more mineral fertilizer was used in mass. Almost all the biogas plants were shut down except two: that in Reusch/Hohenstein (1959) and the Schmidt-Eggersgluess plants close to the monastery of Benediktbeuren, built around 1955.
This plant, consisting of two digesters, one storage tank, a gasholder, and the turbine house, was originally constructed for 112 animal units (GVE) and a gas production of 86 400 m3a-1. In the last few years, however, it was only used for about 55 GVE. The plant cost was 72 000 US$ but it has cost around 12 000 US$ for maintainance annually during the past 25 years. The ratio of straw chaff to the excrement and urine was 1 - 2. The dung was flushed into a dump, mixed with anaerobic sludge, and pumped daily into the digestors. The principle of the "change container" procedure is that while the material digested in the first fully filled fermenter for ca. 20 days, the second was filled. If the second container was full, the content of the first digestor was transferred into the storage tanks. In that way the first digestor was refilled while material was digesting in the second container.
Temperatures of 38-39 °C were considered as optimal for the digestion. The resulting biogas was used in the monastery kitchen for cooking. Any surplus was connected to a 70-HP MAN diesel engine. In the end, however, the plant was shut down in 1979 when cattle breeding was abandoned.
Second attempts at using biogas
In 1970 the demand for biogas increased, driven by the oil crisis. The number of facilities went up to 15 in Bavaria and up to 10 in Baden-Wuerttemberg.
Later, in the 1990s, biogas technology was stimulated for two reasons:
• The profitability ofusing power derived ofbiogas
• The recycling management and Waste Avoidance and Management Act which was implemented in 1994 and resulted in higher costs for disposal of solid waste.
The agricultural sector observed the trend and accepted it very conditionally, since the biogas facilities did not work in a profitable way, mainly because of the high costs in constructing the facilities. Only after the farmers had learned to work themselves and to pool their experience were the facilities run economically.
|
Number of biogas plants |
Mg of digested waste per year | |
|
Austria |
10 |
90 000 |
|
Belgium |
2 |
47 000 |
|
Denmark |
22 |
1 396 000 |
|
Finland |
1 |
15 000 |
|
France |
1 |
85 000 |
|
Germany |
39 |
1 081 700 |
|
Italy |
6 |
772 000 |
|
Netherlands |
4 |
122000 |
|
Poland |
1 |
50 000 |
|
Spain |
1 |
113 500 |
|
Sweden |
9 |
341 000 |
|
Switzerland |
10 |
76 500 |
|
England |
1 |
40 000 |
|
Ukraine |
1 |
12000 |
|
Total |
108 |
4241 700 |
In 1954, Ross, in Richmond, USA, reported about the process of digesting communal waste with sludge. Apparently, a closed facility was running in Chicago, USA, to digest the waste.
At the end of the 1990s, numerous plants were built and implemented for the mechanical-biological treatment of garbage. The technology was based on anaerobic with some aerobic composting. The aerobic process proved to be advantageous, since it enabled enough energy to be provided to run the plant itself.
Not only Germany but other European countries applied the same technology for the disposal of waste (Table 3.1). For example, in Denmark several large biological gas facilities were built for processing of liquid manure together with residues from the food industry.
About 44 anaerobic fermentation plants with a capacity of about 1.2 Mio Mg bio waste in total existed in Germany in April 1999. Of these plants, 31 were running by the wet-fermentation procedure (18 single - stage, 13 multi-stage procedures); the other 13 facilities worked according to the dry-fermentation process (9 singlestep, 4 multi-level procedures). At the same time, around 550 aerobic bio waste composting plants were functioning, with an overall capacity of approximately 7.2 Mio Mg bio waste.431
32 | 3 History and status to date in Europe 3.3
Third attempts at applying biogas
In 2000, the law of "Renewable Energies", which stated the rules for the subsidization of the power supplied by biogas facilities, became effective. Over the past few years, the number of biogas facilities has continuously been rising, especially after implementing even higher subsidies. About 1500 biogas facilities were in use in Germany, most of them in Bavaria.
Electrical power was supplied from biogas into the network out of the sources shown in Table 3.2.
Status to date and perspective in Europe
In the year 2005 in Austria a biogas plant were constructed to feed 10 m3h-1 crude biogas (giving to 6 m3h-1 clean biogas) into the natural gas network, equivalent to 400MWha-1.44) The gas is produced from the excrement ofca. 9000 laying hens, 1500 poultry, and 50 pigs. In Sweden, communal vehicle fleets and even a train are running on biogas.45'
In Germany, the number of biogas plants has increased during the past few years following a governmental promotion handed out for the installation of plants. In fact the number was tripled from 850 plants connected to the electricity network in 1999 to 2700 plants to date in 2006 (Figure 3.3) . In the agricultural sector alone, more than 600 plants were put on stream in 2006, contributing to a total power output of 665 MW and a total energy generation of 3.2 TWh provided by all biogas plants. It is planned to construct 43 000 biogas plants in Germany until the year 2020.
Almost all waste water is already fed into central sewage water treatment plants area-wide with facilities to produce sewage gas. Several small plants with a volume of waste water of less than 8 m3 per day still exist. The objective is, however, to integrate these, too, into the central system as soon as the appropriate pipework is installed.
|
Number |
Installed electric power [MW] |
1000MWha-1 | |
|
Sewage gas |
217 |
85 |
61 |
|
Landfill gas |
268 |
227 |
612 |
|
Biogas |
1040 |
407 |
127 |
|
Total |
1525 |
407 |
1000 900 800 700 _ 600 g 3500 
number of biogas plants --installed electrical power in 1000 kW Figure 3.3 Expansion of biogas production in Germany.46' 400 g 200 100 0 300 T" o number of biogas plants --installed electrical power in 1000 kW Figure 3.3 Expansion of biogas production in Germany.46' Overall, the agricultural sector is seen to be a rich source of biomass. Projections suggest that the agricultural waste alone will enable more than 220 000 additional individual plants and communal facilities to be run, provided that an investment of 25-40 bn US$ is allocated. This will provide farmers the opportunity to become more independent from the food trade and get additional incomes working as "energy farmers". For example, in Hungary in December 2005 a biogas plant with a capacity of 2.5 MW was inaugurated. The plant is fed with liquid manure from several cattle farms and wastes from poultry farming. |
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