Biogas Production for Energy in Germany -Residues from Food Industry-

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Biogas Production for Energy in Germany-Residues
from Food Industry-

• Prof. Dr. Bernd Stephan
• University of Applied Science
• Bremerhaven, Germany

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Anaerobic Digestion Biogas History

• History in Germany starting with utilization of
  marsh gas in the 19th 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)

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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

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Biogas Production process the main steps

• Collection and (pre)treatment
• Producing a slurry with balanced composition
  (e.g. water-content, total organic solids. C/N
  ratio)
• Feeding of reactor with constant rate
• Keeping fermenter at nearly constant temperature
  of about 33o Centigrade
• Mixing of substrate during fermentation
• Gas collection, purification, utilization (heat
  and electricity)
• Collection and utilization of fermented slurry
  e.g as high value organic fertilizerer

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Potential of Biogas (Wilfert, R. et al.,
Institut für Energetik und Umwelt Leipzig, 2002)

• total (PJ/year) electric. (TWh/a)
• 96.5 7.2
• 65-113 4.9-8.5
• 6.4-12.2 0.5-0.9
• 6.4-12.2 0.4-0.8
• 12.5 0.9
• 78.7 5.9
• 265.1-324.9 19.8-24.2

• Animal excreta 4.5
• Vegetable residues from 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)

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Food industry with suitable substrates some
examples

• Slaughterhouses
• Canneries
• Diaries
• Distilleries
• Breweries
• Starch production
• Sugar industry
• Big restaurants/kitchens

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Biogas plant implemention in Germany (1)

• Today nearly all biogas plants in Germany
  designed and operated for residues of food
  industry use mixed substrates as feeding material
• 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 and waste management
• Nearly all plants produce electricity and use the
  excess thermal energy for specific purposes

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Biogas plant implemention in Germany (2)

• The number of plants increased during the last
  years 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

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Biogas plant implemention in Germany (3)

• Plant design depends on substrate properties
• Typical patterns are mesophilic fermentation of
  a slurry, normally with a pretreatment facitity
  (collection unit with mechanical components for
  mixing) and a storage tank for the fermented
  material
• Fermenters are totally mixed air-tight reactors
  with integrated heating systems and thermal
  insulation, in some cases (e.g. low content of
  organic matter) up-flow reactors are used or
  flotation as pretreatment (concentration of
  organic matter)
• The collection tank usually has a storage
  capacity for some days of operation
• Retention time for fermentation is in the range
  of 20 to 30 days
• Power station to produce electricity (gas engine
  coupled with generator)

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Biogas plant implemention in Germany (4)

• Low pressure gas storage, integrated into the
  fermenter (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

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Planning Data 1 (general)

• Biogas potential total organic solids () m3
  CH4/m3 substrate
• Waste water, municipal 0.05 0.15
• Waste water, food industry 0.15 0.5
• Sewage sludge 2 5 to 10
• Cow manure 8 20 to 30
• Pig manure 6 to 8 30 to 50

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Planning Data 2 effluent of slaughterhousesSubs
trate mixture of cow manure and slaughterhouse
waste waterQuantity 50 m3 per daycontent of
organic matter 4gas producion per day 1000
to 1500 m3Energy production 6000 to 9000 kWh
per day,1/3 electrical, 2/3 thermal
energyRetention time 20 daysDigester volume
1000 m3
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Contributions of Biogas for Energy Supply 2004

• The potential of biogas for producing
  electricity comes to 4 of the annual consumption
  of electric energy (public grid)
• The contributions today comes to 0,002 of the
  potential only great potential

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Reasons

• Regional pattern of substrate availability and of
  (local) energy demand
• Distribution cost
• Biogas technology had its great start up since
  2000
• Internal utilization of electricity

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Installed electrical capacity (MW)1999 502000
752001 1102002 1602003 2202004 2702005
350 (estimated)
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Example of Implementation- a typical cluster -

• Biogas plant using agricultural waste,
  slaughterhouse waste and sewage sludge
• Thermal energy used for slaughterhouse
• Electrical energy sold to the public grid at
  subsidies prices

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Biogas plant Brensbach
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Basic Data(plant under construction, some
figures estimated)

• Digester volume 4 800 m3
• Mesophilc process 33-35 oC
• Retention time 20 days
• Input (organic dry matter) 9 600 to 14 400
  kg/day
• Treated slurry 80 000 m3/year
• Sludge utilization liquid fertilizer
• Energy output 3000 to 4500 m3/day
  6 to 9 million kWh/year
• electrical 2 to 3 million kWh/year thermal
  4 to 6 million kWh/year

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Some aspects

• Great market potential
• Cost reduction for plant components with
  increasing implementation
• Positive effects by standardization, increasing
  skillness/experience and competition of
  biogas-companies
• Cost of substrates/cosubstrates will go up
• Energy crops from East Europe?
• Phosphate recovery from fermented sludges?

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Some Aspects for Future Biogas Development in
Thailand

• 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