Transcript Document

Biogas Production for Energy in
Germany
-Residues from Food Industry-
Prof. Dr. Bernd Stephan
University of Applied Science
Bremerhaven, Germany
Anaerobic Digestion: Biogas History
• History in Germany starting with utilization of „marsh gas“ in the 19th
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century: gas tight drums with an diameter of about 2 to 3 meter were
placed upside down into the wet lands for gas collection and gas utilization
for cooking – similar to the Indian Gabor Gas Plant
Beginning around 1920 trucks of public services were operated with
compressed biogas from digestion of sewage sludge – in the fifties ot the
20th century this was given up due to low cost mineral oil
In the fifties last century some farmers build biogas plants for the treatment
of aninmal wastes – the technology was based on different principles
The oil price crisis in the seventies stimulated broad activities on the
research and implementation side of agricultural biogas plants and resulted
in optimized plant design and process performance. About 200 plants were
bulit and operated at that time, but could not compete with the market
prices for gas or liquid hydrocarbons.
The energy policy of German Federal Government now subsidies the
utilization of renewables – a result the market for big biogas plant goes up
(most of them are connected to cogeneration plants)
Basics
Substrates must be degradable
Substrates must/should be available at a constant
mass/volume flow
Substrates should have a nearly constant
composition
Concentration of organic dry matter should be
higher than 2 %
Substrates should be a liquid slurry
Digester volume should be more than about 100m3
Potential of Biogas
(Wilfert, R. et al., Institut für Energetik und Umwelt Leipzig, 2002)
• Animal excreta
• Vegetable residues from
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4.5
agriculture
3.0-5.3
Wastes from Industry
0.3-0.6
Waste from parks and gardens
0.3-0.6
Organic municipal waste
0.6
Energy crops
3.7
TOTAL
12.7-15.3
(billion m3/a)
total (PJ/year)
96.5
electric. (TWh/a)
7.2
65-113
6.4-12.2
4.9-8.5
0.5-0.9
6.4-12.2
12.5
78.7
265.1-324.9
0.4-0.8
0.9
5.9
19.8-24.2
Food industry with suitable substrates –
some examples
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Slaughterhouses
Canneries
Diaries
Distilleries
Breweries
Starch production
Sugar industry
Big restaurants/kitchens
Biogas plant implemention in Germany (1)
• Today nearly all biogas plants in Germany designed and
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operated for residues of food industry use mixed
substrates:
cofermentatation of agricultural waste, effluents with
organic load from food industry and similar facilities,
energy crops, organic residues from the households
Plant size and technology depend on the specific
substrate mixture and pattern of energy utilization
Nearly all plants produce electricity and use the excess
thermal energy
Biogas plant implemention in Germany (2)
• The number of plants increased during the last years
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from about 190 in 1992 to about 2000 in 2004
Installed electrical capacity increased from 50 MW per
year in 1999 to about 270 MW per year
In North-East Germany 70 % of the plants treat more
than 7500 m3 of slurry per year, the average treatment
capacity in Germany is in the range of 1000 to 2000 m3
per year
Biogas plant implemention in Germany (3)
• Plant design depends on substrate properties
• Typical patterns are: mesophilic fermentation of a slurry, normally
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with a pretreatment facitity (collection unit with mechanical
components for mixing) and a storage tank for the fermented
material
Fermenters are totally mixed airtight reactors with integrated
heating systems and thermal insulation, in some cases (e.g. low
content of organic matter) up-flow reactors are used
The collection tank usually has a storage capacity for some days of
operation
Retention time for fermentation 20 to 30 days
Power station to produce electricity (gas engine coupled with
generator)
Biogas plant implemention in Germany (4)
• Low pressure gas storage, integrated into the fermenter
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(gas cap) or separated
Gas consumption directly after production
Biogas is dewatered and desulfurized before combustion
Most of the engines (70 %) are modified diesel engines,
which use a jet of gas oil for ignition of biogas
Excess heat is used to warm up water for specific
purposes e.g. heating of the fermenter, buildings,
process water for cleaning or for food processing
Planning Data 1
Biogas potential:
Waste water, municipal
Waste water, food industry
Sewage sludge
Cow manure
Pig manure
total organic solids (%)
0.05
0.15
2
8
6 to 8
m3 CH4/m3 substrate
0.15
0.5
5 to 10
20 to 30
30 to 50
Planning Data 2
Substrate: mixture of cow manure and slaughterhouse waste water
Quantity: 50 m3 per day
content of organic matter: 4%
gas producion per day : 1000 to 1500 m3
Energy production: 6000 to 9000 kWh per day,
1/3 electrical, 2/3 thermal energy
Retention time: 20 days
Digester volume: 1000 m3
Contributions of Biogas for Energy Supply
2004
• The potential of biogas for producing electricity
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comes to 4% of the annual consumption of
electric energy (public grid)
The contributions today comes to 0,002 % of
the potential
Reasons
• Regional pattern of substrate availability
and of energy demand
• Distribution cost
• Biogas technology had its great start up
since 2000
• Internal utilization of electricity
Installed electrical capacity (MW)
1999
2000
2001
2002
2003
2004
2005
50
75
110
160
220
270
350 (estimated)
Example of Implementation
- a typical cluster -
• Biogas plant using agricultural waste,
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slaughterhouse waste and sewage sludge
Thermal energy used for slaughterhouse
Electrical energy sold to the public grid at
subsidies prices
Biogas plant „Brensbach“
Some aspects
• Great market potential
• Cost reduction for plant components with
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increasing implementation
Positive effects by standardization, increasing
skillness/experience and competition of biogascompanies
Cost of substrates/cosubstrates will go up
Energy crops from East Europe?
Phosphate recovery from fermented sludges?
Some Aspects for Future Biogas
Development in Thailand
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Analysis of Potential for implementation
Cofermentation (are there „biogas clusters“?)
Energy demand electrical and thermal in agro industry
Gas Separation CH4/CO2: e.g. compressed methan as
fuel for automotives; CO2 for industriy (e.g.beverages)
• Improvement of fertility of soil
• Used oils from kitchen and residues of restaurants
• Future environmental policy for cities should focus on
biogas too as a decentralized system for waste treatment