The administration and performance evaluation of biogas plants in Germany

1. 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

2. 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

3. 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)

4. 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

5. 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

6. 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

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

8. 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?

9. Characterization of substrates

10. Biomass / Substrates Organic waste Energy crops By-products & Residues

11. 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)

12. 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!

13. Methods of substrate´s characterization Animal nutrition analysis Continuous anaerobic digestion Discontinuous anaerobic digestion

14. Methods of substrate´s characterization Representativesamplesofthebiomassare essential formeaningfulresults!

15. Biogas potential

16. 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

17. 2. main state of the art technologies

18. 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

19. 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

20. Continuously stirred tank reactor (CSTR)

21. Plug Flow Tank Reactor (PFTR) vertical horizontal Intake Discharge

22. Batch Reactor Garage type digester discontinuous Prozeßschema Boxenfermenter (Abbildung: BEKON GmbH Co. KG); Fotos: Bekon GmbH (oben), DBFZ (unten)

23. 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

24. 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

25. Losses/Emissions

26. 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

27. 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

28. 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)

29. 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)

30. 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

31. 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!

32. 4. Evaluation of the overall biogas plant concept

33. 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

34. 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?

35. 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