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Biochar Structure, Stability, and Sequestration Alice Budai April 2011 Image from www.nationalgeographic.com.

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Presentation on theme: "Biochar Structure, Stability, and Sequestration Alice Budai April 2011 Image from www.nationalgeographic.com."— Presentation transcript:

1 Biochar Structure, Stability, and Sequestration Alice Budai April 2011 Image from

2 Outline Motivation behind Biochar Research –Why focus on Stability? Not all chars are created equal Biochar characterization –Objectives –Hypotheses Biochars of the project –Feedstock and pyrolysis methods Characterization Methods Methods of stability estimation Image from

3 The CO 2 problem Figure from Wikipedia and Dr. Pieter Tans Atmospheric concentrations of carbon dioxide have increased from 280 to 390 ppm The rate of change of CO 2 in the atmosphere is increasing over time Only 50% of anthropogenic CO 2 emissions are naturally sequestered Anthropogenic sequestration could be applied to pick up the slack

4 Carbon Cycle Perspective Estimated fluxes Fosslil fuel combustion (+6,3 Gt/yr) Net ocea and land uptake (-3,1 Gt/yr) Atmospheric Accumulation (-3.2 Gt/yr) Estimated flux from soil (50-60 Gt/yr) 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 Intergovernmental Panel on Climate Change, edited by J. T. Houghton, et al., Cambridge University Press, Cambridge, UK Soils have a great potential to sequester carbon

5 The CO 2 solution By pyrolyzing biomass it becomes more recalcitrant and can be used to store carbon in soil How much CO 2 could be sequestered using purposeful biochar production and application to soil? Images from and Adam

6 Not all Biochars are created Equal Biochar properties are determined by the biomass Pore size and distribution is determined by the feedstock (cell) structure Surface area and internal volume are thus determined Mineral-contents vary among feedstocks Images from and ”Biochar: Environmental Management” (edited by Lehmann and Joseph, 2009)

7 Not all Biochars are created Equal Biochar properties are determined by pyrolyis conditions Prominent Factors: –Temperature HTT, rentention –Pressure –Fluidizing agent –Degree of oxidation Mechanisms: –O, H, C, and minerals (K, Ca, N, P, Al, S,…) are volatilized at different rates –The remaining C molecules rearrange Image from ”Biochar: Environmental Management” (edited by Lehmann and Joseph, 2009)

8 Characterizing Chars According to Structure Physical and chemical characterisitics According to Function Phenomenological abilities to improve plant growth and microbial processes Ability to store carbon

9 Main Objectives To detect structural (chemical) differences in biochars using advanced analysis techniques To detect structural (chemical) changes after incorporation into soil using advanced analyses To measure the stability of biochars using laboratory incubation and natural abundance carbon isotopes To link the structure of biochar to its stability in soil, and to identify a proxy for stability

10 Hypotheses The production method (carbonization/pyrolysis) influences biochar’s stability and structure –Higher temperature chars are expected to be more recalcitrant, consisting of aromatic rings instead of O-alkyl carbon, affecting surface properties of the biochar and its behavior in soil –More intensive pyrolysis methods will lead to more stable biochars –Structural characteristics will affect stabilization behavior of the char (binding to organic matter and clay) –An incubation study of biochar with soil over 1,5 years will reflect the ratio of labile to recalcitrant carbon

11 Biochars of this project Two C4 feedstocks 280 x miscanthus140 x corn cob Two C4 feedstocks will be utilized

12 Biochars of this project (continued) Three production methods –Slow pyrolysis (including a temperature gradient) –Flash pyrolysis –Hydrothermal carbonisation NTNUHNEIMPG

13 Characterization Methods Elemental Analysis –Weight % of C, H, O, N, S Proximate Analysis –Moisture content –Volatile content –Free carbon remaining –Ash (mineral content) TG –Mass change of a material as a function of temperature DSC –Thermal stability and decomposition Figure from Morten Grønli

14 Characterization Methods (..continued..) CEC –Ability of the material surface to bind ions BET –Surface area of the material SEM –Surface topography –Composition –Other, electrical conductivity Image from ”Biochar: Environmental Management” (edited by Lehmann and Joseph, 2009)

15 Characterization Methods (..continued) Spectrometry (NMR and NIR/MIR) –Chemical structure Charcoal shown in red, forest soil shown in blue and green BPCA –Degree of condensation of the aromatic rings Sources: Brennan et al, 2001 and Line Tau Strand

16 Elucidating Stability through Stable Isotopes The isotopic signature of carbon in biochar produced from C4 plants is noticeably different from that of organic matter in Norwegian soil –This natural abundance labeling will be used to identify the source of respired CO 2 during incubation It will be assumed that biochar is composed of a labile and recacitrant carbon pool Based on the kinetics and  13 C of CO 2 respired, and changes in biochar structure over time, the stability and size of the reacalcitrant pool will be estimated Image from

17 Summary of main objectives Identification of a proxy (measurable chemical property) for biochar stability Development of a fast/easy characterization method that could be used to control the quality of biochars on the market


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