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The 3rd International Cooperation Conference on Biogas Industrialization in China (Organizers: CAAA, DLG, CBS) 19.05.2012 Nanjing, China . The administration and performance evaluation of biogas plants in Germany. Jan Postel, Dr . Britt Schumacher, Dr. Jan Liebetrau.

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slide1

The 3rd International Cooperation Conference on Biogas Industrialization in China (Organizers: CAAA, DLG, CBS)

19.05.2012 Nanjing, China

The administration and performance evaluation of biogas plants in Germany

Jan Postel, Dr. Britt Schumacher, Dr. Jan Liebetrau

performance evaluation of biogas plants
Performance evaluation of biogas plants

Efficiency: Ratio of actual power output and power input

What is required to evaluate a biogas plant?

  • Mass balance of in- and output
  • Energy balance of the biogas plant, including in- and output
  • Data of the reliability of the equipment (hours/year)

What is needed for the mass/energy balances and the reliability data?

  • Characterization of substrates
  • Main state of the art technologies (data acquisition)
  • Losses/Emissions
  • Evaluation of the overall biogas plant concept
performance evaluation of biogas plants process chain

Excrements

Preliminary

tank

Biogas

Energy crops

Biogas-

utilization

Silo

Digester

Substrate-

storage

Substrate-

Feed in

Digestate

Distribution/Application digestate

Gas-

storage

Storage tank (digestate)

Performance evaluation of biogas plants (processchain)

What is required to evaluate a biogas plant?

  • Mass balance of in- and output
  • Energy balance of the biogas plant, including in- and output
  • Data of the reliability of the equipment (hours/year)

e.g. combined heat and power plant (CHP)

requirements for energy balances as basis for efficiency evaluation
Requirementsforenergybalancesasbasisforefficiencyevaluation
  • Efficiency: Ratio of actual power output and power input
  • What is necessary for a qualified evaluation?
    • Definition oftheoreticalenergyoutput
    • Evaluation, documentation, quantification of mass and energy streams,

Evaluation of operational hours, (documentation of down times, flaring events, maintenance periods etc. )

    • Calculation of capacity utilization
    • Actual – theoretical comparison
    • Identification of bottlenecks
    • Optimization
mass balance
Mass balance

Grass silage

Digester

Cattle Manure

Digestate

Inorganic matter

Organic matter

Water

Water vapour

Carbondioxid

Methane

Documentation and quantification of all relevant mass streams

mass balances evaluation
Mass balancesevaluation
  • Does the quality and amount of input masses realized in practice meet the design assumptions?
  • Is the Biogas production according to the theoretical value?

(consider the conversion efficiency within the CHP as important factor if no direct quantification of the biogas mass flow is available!!)

    • If not check:
      • Substrate quality (is the assumed biogas potential correct?)
      • Infeedamountcorrect?
      • Quantification of degree of degradation by means of a gas potential test of the digestate
      • Stability of biological process (acid concentration?)
      • Temperature
      • Inhibition effects
      • Leackageofbiogaswithinthe gas collectionsystem
energy balance
Energybalance

A high degree of utilization of waste heat from the CHP is of enormous relevance for the overall efficiency

energy balance evaluation
Energybalanceevaluation
  • Istheenergyoutputasexpected?
  • Electrical:
  • If not check:
    • Biogas productionasassumed?
    • CHP unit – conversionefficiencyasassumed?
    • Consumptionofdevices on siteto large?
    • Downtime - whatarebottlenecksoftheprocess?
  • Thermal:
  • If not check:
    • Losses due topoorinsulation?
    • Are thereotheroptionsforheatutilization?
biomass substrates
Biomass / Substrates

Organic waste

Energy crops

By-products & Residues

substrate characteristics
Substrate characteristics
  • Gas potential (maximum biogas yield obtainable) measured or calculated (digestion tests, animal nutrition test, elementary analysis)
  • Degradation rate (reduction of the concentration of organic substance)
  • Content of micro (trace) and macro elements
  • Content of potential inhibitory substances as nitrogen, sulphur, antibiotics etc.
  • Material handling: pumpability, content of disturbing material (e.g. sand, stones)
characterization of substrates composition
Characterizationof Substrates - Composition
  • Dry matter content (DM): waterless (anhydrous) share of a mixture after drying at 105 °C.
  • Organic dry matter content (oDM): Mixture free of water (anhydrous) and free of inorganic substances generally per dryingat105 °C and annealing at 550 °C
  • Fractions of fat, protein and carbohydrate analyzed by “Weender” – Animal nutrition analysis

Representativesamplesofthebiomassare essential formeaningfulresults!

methods of substrate s characterization
Methods of substrate´s characterization

Animal nutrition analysis

Continuous anaerobic digestion

Discontinuous anaerobic digestion

methods of substrate s characterization1
Methods of substrate´s characterization

Representativesamplesofthebiomassare essential formeaningfulresults!

characterization of substrates conclusion
Characterization of Substrates - Conclusion
  • Substrates differ in energy density, composition and degradability
  • Mostly pre-treatment enhances the degradability of substrates, except for lignin, which is only aerobic degradable
  • High amounts of extreme easy degradable substrates can lead to process failure, due to a excessive acid production
  • Mono-fermentation can lead to an unbalanced nutrient supply, therefore a suitable mixture of substrates or a supply with lacking nutrients are recommendable
  • High concentrations of ammonia can lead to difficulties in the biological process
  • High concentrations of sulphur can cause damage e.g. CHP
  • Sand and stones can lead to technical difficulties
general technical requirements
General technical requirements
  • high reliability/durability and short maintenance interruptions of all plant components are essential for high operating and full load hours – the overall process has to be reliable!
  • Technology has to match the substrate/biomass, sufficient flexibility for change in substrate
  • Capacityofthe plant as a wholeandthe plant componentshavetomatchtheactualsubstrateandmassflows
  • Low energy consumption
  • Easy to monitor and control
biomass and reactor type
Biomass and reactor type
  • Digester type is selected according to the substrate characteristics
  • Agricultural application TS between 3 – 12 % continuous stirred tank reactor (CSTR), manure and energy crops
  • plug flow digesters mostly for higher total solid concentrations
  • Box/garage type digestion only for biomass, which is stackable and can be easily saturated by percolate (landscape management material, separately collected biowaste), highly insensitive to sand, rocks, disturbing material
plug flow tank reactor pftr
Plug Flow Tank Reactor (PFTR)

vertical

horizontal

Intake

Discharge

batch reactor
Batch Reactor

Garage type digester

discontinuous

Prozeßschema Boxenfermenter (Abbildung: BEKON GmbH Co. KG); Fotos: Bekon GmbH (oben), DBFZ (unten)

process evaluation
Processevaluation

Laboratory tests

Online measurement

Input

Gas production rate

pH-value

Methanecontent

Carbondioxidcontent

Hydrogen content

Temperature

Permanent available,

easy integration to automated process

information content???

  • Degradation of VS, TS, TOC, COD
  • Content oforganicacids(sumparameter)
  • Content oforganicacids (portionofeachacid)
  • not permanent available
  • need of sampling
  • time consuming,
  • difficult to automate,
  • high information content
technologies conclusion
Technologies - Conclusion
  • Energy output depended on many factors (substrate qualities, stability of biological process, efficiencies and availabilities technical devices)
  • Primary target should be: process stability, reliability of technology
  • Secondary target: gas production rate and energy output
  • The energy consumption of all devices should be kept by a minimum
  • A high degree of utilization of waste heat from the CHP is of enormous relevance for the overall efficiency
losses emissions1
Losses / Emissions
  • Losses reduce the energy output and lead to emissions (gaseous, liquid, solid)
  • Need to minimize losses to
    • prevent environmental pollution
    • avoid the release of greenhouse gases
    • prevent the release of toxic substances
    • ensure high energy efficiency
    • ensure economical operation
sources of emissions within the process chain

Excrements

Preliminary

tank

Biogas

Energy crops

Biogas-

utilization

Silo

Digester

Substrate-

storage

Substrate-

Feed in

Digestate

Distribution/Application digestate

Gas-

storage

Storage tank (digestate)

Sourcesofemissionswithintheprocesschain

Elevated N2O und

NH3-Emissionsdue to crop growing ?

Humus balance?

methane losses of the plant?

Nutrition balance?

No data available - preliminary tank

Leakages?

Methane losses –

Biogas upgrading?

Emissions- from the Co generation unit ?

Coverage?

Relief pressure valve?

Silage losses5-20% ?

Emissions not extensivelyinvestigatedyet

dependend on substrates, moisturecontentofthesoil,

climate, time andperiodofapplication

Large variations in N2O emissions

e.g. Methane emissions from open storage tanks;

Dependend on processing + substrates

Emissions influenced by distribution techniques

possible losses i
Possible losses I
  • Silage storage facilities
      • Respiration and decomposition of organic matter
  • Hopper/ preliminary tank/ open hydolysis
    • Hopper used for mixing of substrate with digestate
      • Methane (CH4), Hydrogen (H2)
    • Solid material feed in device
      • Respiration and decomposition of organic matter
  • Digester
    • Permeability of rubber membrane, leakages and pressure relief valves
      • Mainly Methane (CH4)
possible losses ii
Possible losses II
  • Storage tank (digestate)
      • Methane (CH4), nutrients (fertilizer value) (NH3,(N2O))
  • Gas utilization
    • Co generation unit
      • Mainly Methane (CH4) and unburnthydrocarbon (CnHm)
    • Upgrading facilities (Feed in with natural gas quality)
      • Methane slip (CH4)
gas potential of digestates
Gas potential of digestates

Specific biogas yield (l*kgVS-1)

Time (d)

Low retention times lead to incomplete substrate utilization

For comparison: 18-70 m³/t digestate

3 losses emissions conclusion
3. Losses / Emissions - Conclusion
  • due to environmental and economic reasons losses should be avoided
  • Plant design, substrate and operation of the plant affect the amount of losses
  • Frequent check of the plant and operational management should be self-evident
  • Actual – theoreticalcomparisonisneededforpreciseidentificationoflosses!
evaluation for optimization
Evaluation for Optimization

Aim: Achievingof a definedtargetstate (optimum) by well-directedmodificationofcurrentsituation

Noindependentoptimizationofisolateditemspossible, due to mutual dependency

  • Availability
  • Capacityutilization
  • Efficiency
  • Procedure
  • Processcontrol
  • Investment costs
  • Operational costs
  • Income
  • Greenhouse gas emissions
  • Odouremissions
  • Noise emissions

Source: Leitfaden Biogas; www.fnr.de

4 evaluation of the overall biogas plant concept conclusion
4. Evaluation of the overall biogas plant concept - Conclusion
  • Are technology and substrates (texture/amount) a good match?
  • Which ratio of energy production to energy consumption is achievable? (electricity and heat)
  • Fits the plant to operational needs, infrastructure and consumers - gas, electricity and/or heat grid?
  • Are collection and documentation of data appropriate to avoid malfunction?
  • Are the losses reduced to a minimum?
  • Which climatic conditions are to consider? Are insulation or cooling needed?
  • Are the distances between biogas plant and substrates source respectively between biogas plant and residues application short enough? (logistics, costs)
  • Are aspects of environmental protection to consider?
slide35

Contact:

Dr.-Ing. Jan Liebetrau

Jan Postel

Dr. Britt Schumacher

Deutsches BiomasseForschungsZentrum German Biomass Research Centre

Torgauer Straße 116

D-04347 Leipzig

www.dbfz.de

Tel./Fax. +49(0)341 – 2434 – 112 / – 133

Thank you very much for your attention!

Research for the Energy of the Future

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