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Biochar Structure , Stability , and Sequestration Alice Budai April 2011

Biochar Structure , Stability , and Sequestration Alice Budai April 2011. Image from www.nationalgeographic.com. Outline. Motivation behind Biochar Research Why focus on Stability ? Not all chars are created equal Biochar characterization Objectives Hypotheses Biochars of the project

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Biochar Structure , Stability , and Sequestration Alice Budai April 2011

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  1. BiocharStructure, Stability, and SequestrationAlice BudaiApril 2011 Image from www.nationalgeographic.com

  2. Outline • MotivationbehindBiochar Research • WhyfocusonStability? • Not all charsarecreatedequal • Biocharcharacterization • Objectives • Hypotheses • Biocharsoftheproject • Feedstock and pyrolysismethods • CharacterizationMethods • Methodsofstabilityestimation Image from www.forskning.no

  3. The CO2 problem • Atmosphericconcentrationsofcarbondioxide have increased from 280 to 390 ppm • The rate ofchangeof CO2 in theatmosphere is increasing over time • Only 50% ofanthropogenic CO2emissionsarenaturallysequestered • Anthropogenicsequestrationcould be applied to pick up theslack Figure from Wikipedia and Dr. Pieter Tans

  4. CarbonCyclePerspective Estimatedfluxes • Fosslilfuelcombustion(+6,3 Gt/yr) • Net ocea and land uptake (-3,1 Gt/yr) • AtmosphericAccumulation (-3.2 Gt/yr) • Estimatedflux from soil (50-60 Gt/yr) Soils have a greatpotential to sequestercarbon Image from: Rice University, based on data from Prentice IC, et al (2001), The Carbon Cycle and Atmopheric Carbon Dioxide, in Climate Change 2001,The Scientific Basis. Contributions of Working Group 1 to Third Assessment Report of the IntergovernmentalPanel on Climate Change, edited by J. T. Houghton, et al.,Cambridge University Press, Cambridge, UK

  5. The CO2solution • By pyrolyzingbiomass it becomes more recalcitrant and can be used to store carbon in soil • Howmuch CO2could be sequesteredusingpurposefulbiocharproduction and application to soil? Images from www.news.cornell.edu and Adam

  6. Not all BiocharsarecreatedEqualBiocharpropertiesaredetermined by thebiomass • Pore size and distribution is determined by thefeedstock (cell) structure • Surface area and internalvolumearethusdetermined • Mineral-contentsvaryamongfeedstocks Images from www.airterra.com and ”Biochar: Environmental Management” (edited by Lehmann and Joseph, 2009)

  7. Not all BiocharsarecreatedEqualBiocharpropertiesaredetermined by pyrolyisconditions • Prominent Factors: • Temperature • HTT, rentention • Pressure • Fluidizing agent • Degreeofoxidation • Mechanisms: • O, H, C, and minerals (K, Ca, N, P, Al, S,…) arevolatilized at different rates • The remaining C moleculesrearrange Image from ”Biochar: Environmental Management” (edited by Lehmann and Joseph, 2009)

  8. CharacterizingChars According to Structure Physical and chemicalcharacterisitics According to Function Phenomenologicalabilities to improve plant growth and microbialprocesses Ability to store carbon

  9. Main Objectives • To detectstructural (chemical) differences in biocharsusingadvancedanalysistechniques • To detectstructural (chemical) changesafterincorporationintosoilusingadvanced analyses • To measurethestabilityofbiocharsusinglaboratoryincubation and naturalabundancecarbon isotopes • To link thestructureofbiochar to itsstability in soil, and to identify a proxy for stability

  10. Hypotheses • The productionmethod (carbonization/pyrolysis) influencesbiochar’sstability and structure • Highertemperaturecharsareexpected to be more recalcitrant, consistingofaromatic rings insteadofO-alkylcarbon, affectingsurfacepropertiesofthebiochar and itsbehavior in soil • More intensive pyrolysismethodswill lead to more stable biochars • Structuralcharacteristicswillaffectstabilizationbehaviorofthechar (binding to organic matter and clay) • An incubationstudyofbiocharwithsoil over 1,5 yearswillreflectthe ratio of labile to recalcitrantcarbon

  11. Biocharsofthisproject Two C4 feedstockswill be utilized • Two C4 feedstocks 140 x corncob 280 x miscanthus

  12. Biocharsofthisproject(continued) • Three productionmethods • Slowpyrolysis (including a temperature gradient) • Flash pyrolysis • Hydrothermalcarbonisation NTNU HNEI MPG

  13. CharacterizationMethods • ElementalAnalysis • Weight % of C, H, O, N, S • ProximateAnalysis • Moisturecontent • Volatile content • Freecarbonremaining • Ash (mineral content) TG • Masschangeof a material as a functionoftemperature DSC • Thermalstability and decomposition Figure from Morten Grønli

  14. CharacterizationMethods(..continued..) • CEC • Abilityofthe material surface to bind ions • BET • Surface area ofthe material • SEM • Surfacetopography • Composition • Other, electricalconductivity Image from ”Biochar: Environmental Management” (edited by Lehmann and Joseph, 2009)

  15. CharacterizationMethods(..continued) • Spectrometry (NMR and NIR/MIR) • Chemical structure Charcoalshown in red, forestsoilshown in blue and green • BPCA • Degreeofcondensationofthearomatic rings Sources: Brennan et al, 2001 and Line Tau Strand

  16. ElucidatingStabilitythrough Stable Isotopes • The isotopicsignatureofcarbon in biocharproduced from C4 plants is noticeablydifferent from thatoforganic matter in Norwegiansoil • This naturalabundancelabelingwill be used to identifythesourceofrespired CO2 during incubation • It will be assumedthatbiochar is composedof a labile and recacitrantcarbon pool • Basedonthekinetics and d13C of CO2respired, and changes in biocharstructure over time, thestability and sizeofthereacalcitrant pool will be estimated Image from www.picarro.com

  17. Summaryofmainobjectives • Identificationof a proxy (measurablechemicalproperty) for biocharstability • Developmentof a fast/easycharacterizationmethodthatcould be used to controlthequalityofbiocharsonthe market

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