Biochars Are Not Created Equal:
A Survey of their Physical, Structural, and Chemical
Properties and Implications for Soil ...
Outline

         Physical and Structural Properties
               Specific Surface
               Water Sorption/Reactio...
Physical and Structural Properties
                     Pine Wood Char




                                        Oak Woo...
Physical Properties




                                Slow
                     Slow

                                Fa...
X-ray Diffraction Analysis




                                   Slow Pyrolysis and Hydrothermal Chars
            Gasifi...
Transformations during pyrolysis




Amonette 04Mar2010
                     Keiluweit et al., 2010 EST online
Physical Structure and
  Chemical Properties Depend
  on Carbon Bonding Network




          Radovic et al., 2001
       ...
What if you don’t have a 13C-CP-
                 MAS-NMR, XRD, FIB-SEM or some
                 other super duper DPY-UTH...
Proximate Analysis
    Provides quick sense of
    stability and chemistry in
    three parameters:
                      ...
Ultimate Analysis


         More expensive than proximate analysis
         Measures
               C, H, O, N, S element...
Sum to 100%
     Ultimate Analysis                                                    Volatile   Fixed

                  ...
Van Krevelen Diagram

                                                                    van Kremelen Diagram
         Sh...
FC/VM Ratio




Amonette 04Mar2010
                          H
                              T




                       ...
Modeled half-life (yr) of biochars prepared at different
temperatures from various feedstocks
        Feedstock    250°C  ...
Estimated half-life in soils: effect of
   temperature
                                              Estimates of Half-lif...
Surface Chemistry



                     Slow
                     Fast
                     Gas




         Slow Pyroly...
Surface Chemistry—Boehm titration results
     1200
                                                                      ...
Inferred pH-Dependent Exchange Capacities
                                                              Oak Feedstock


  ...
Hydrophilicity
                                    75

                                                                   ...
Speculations on the best biochar type for
   soil application
       Criteria
              Near-neutral pH
              ...
Acknowledgments
  Thanks to Stefan Czernik, Danny Day, Bob Hawkins, Hal
    Collins, Manuel Garcia-Perez, Doug Elliott, Ma...
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Amonette: Biochar Characterization

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Physical and Structural Properties
-Specific Surface
-Water Sorption/Reaction
-X-ray Diffraction
Chemical Properties
-Bulk (NMR, elemental)
-Recalcitrance
-Surface
-Hydrophilicity
Beneficial Properties for Soil Amendments

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Amonette: Biochar Characterization

  1. 1. Biochars Are Not Created Equal: A Survey of their Physical, Structural, and Chemical Properties and Implications for Soil Application J.E. Amonette*, Y. Hu, N. Schlekewey, S. S. Dai, Z. W. Shaff, C. K. Russell, S. D. Burton, and B. W. Arey jim.amonette@pnl.gov Pacific Northwest National Laboratory, Richland, WA 99352 National Society of Consulting Soil Scientists Amelia Island, FL 04 March 2010 PNNL-SA-71408
  2. 2. Outline Physical and Structural Properties Specific Surface Water Sorption/Reaction X-ray Diffraction Chemical Properties Bulk (NMR, elemental) Recalcitrance Surface Hydrophilicity Beneficial Properties for Soil Amendments Amonette 04Mar2010
  3. 3. Physical and Structural Properties Pine Wood Char Oak Wood Char Corn Cob Char Amonette 04Mar2010
  4. 4. Physical Properties Slow Slow Fast Fast Gas Gasifier Amonette 04Mar2010
  5. 5. X-ray Diffraction Analysis Slow Pyrolysis and Hydrothermal Chars Gasification and (steam present) Fast Pyrolysis Chars Combustion Char (high mineral content) Amonette 04Mar2010
  6. 6. Transformations during pyrolysis Amonette 04Mar2010 Keiluweit et al., 2010 EST online
  7. 7. Physical Structure and Chemical Properties Depend on Carbon Bonding Network Radovic et al., 2001 13CCP-MAS NMR Amonette et al., 2008 Amonette 04Mar2010
  8. 8. What if you don’t have a 13C-CP- MAS-NMR, XRD, FIB-SEM or some other super duper DPY-UTH- ALPHABET-SOUP gizmo . . .??? What are the most cost-effective analyses for routine classification? Amonette 04Mar2010
  9. 9. Proximate Analysis Provides quick sense of stability and chemistry in three parameters: 100 Hydrothermal Volatile matter is mass Slow Pyrolysis lost in heating charcoal 90 Fast Pyrolysis to 950°C in covered Gasification crucible for 6 minutes 80 Ash-Free Line 50% VM/FC Ash content is mass of 70 100% VM/FC residue after combustion 60 Fixed C is remainder Fixed C, % 50 High ash content (KCl, 40 SiO2), seen in corn 30 stovers, wheatstraw, switchgrass, and 20 manure chars (CaO) 10 Increasing Pyrolytic chars tend to Ash 0 Content have VM/FC ratios of 0 10 20 30 40 50 60 0.5 to 1.0 Volatile Matter, % JE Amonette 29 August 2009 Higher fixed C contents suggest greater C stability Amonette 04Mar2010
  10. 10. Ultimate Analysis More expensive than proximate analysis Measures C, H, O, N, S elemental content Moisture content Mineral ash remaining after combustion Used to help classify chars and determine the degree of alteration from original biomass Elemental ratios often plotted to aid classification (e.g., van Krevelen diagrams) Amonette 04Mar2010
  11. 11. Sum to 100% Ultimate Analysis Volatile Fixed LOD C H N O S Ash Matter C Sample % % % % % % % % % HT Grass 2.29 53.83 5.24 2.17 18.40 0.57 22.88 48.92 28.20 HT Wood 4.81 66.20 5.46 2.98 18.62 0.27 7.24 48.20 44.56 WSU S 2.94 46.04 1.74 0.70 14.28 0.23 40.55 19.83 39.62 OKEB 4.03 70.35 3.92 0.42 23.28 0.02 2.88 37.36 55.73 PBEB 4.41 66.75 3.64 0.35 26.08 0.03 3.93 43.35 48.31 PCEB 2.90 72.34 4.42 0.17 21.94 0.02 1.19 41.37 54.54 PCN 2.44 71.25 4.60 0.17 23.51 0.02 0.99 44.63 51.94 CS1 2.33 54.92 2.59 0.90 15.60 0.08 29.51 21.47 46.69 CS2 2.20 36.54 2.20 0.97 17.78 0.09 48.35 22.60 26.85 PNNL-M (MP) 3.30 68.45 3.94 0.25 25.50 0.02 3.29 40.14 53.27 PNNL-P 2.99 72.09 3.88 0.18 23.30 0.02 2.54 36.44 58.03 PNNL-S (SG) 2.75 56.15 2.88 1.08 19.07 0.15 25.77 24.30 47.18 OAK 2.97 79.64 2.68 0.28 15.47 <0.01 3.70 22.75 70.58 WAL 5.50 45.53 0.86 0.49 17.68 1.00 45.11 20.32 29.07 HW 1.02 90.44 1.84 0.24 5.02 <0.01 3.07 8.10 87.81 WS 1.97 53.18 1.64 0.39 8.53 0.17 37.99 8.72 51.32 OK 4.45 53.38 2.34 0.81 14.21 0.09 32.46 17.50 45.59 CSB 2.54 53.41 1.01 0.39 7.08 0.06 41.07 7.64 48.75 Oak 3.62 78.11 2.81 0.31 15.64 0.02 3.74 27.60 68.66 Amonette 04Mar2010
  12. 12. Van Krevelen Diagram van Kremelen Diagram Shows degree of alteration from biomass 0.18 towards pure C 0.16 Path leading to lignite 0.14 Biomass and coal distinct from 0.12 pyrolytic chars H:C Ratio Lignite Hydrothermal 0.10 More energy extracted Slow Pyrolysis 0.08 Fast Pyrolysis during pyrolysis than Coal 0.06 Gasification during “coalification” 0.04 Coal Lignin Minimal alteration for Cellulose 0.02 hydrothermal “chars” 0.00 0.00 0.20 0.40 0.60 0.80 1.00 O:C Ratio Amonette 04Mar2010
  13. 13. FC/VM Ratio Amonette 04Mar2010 H T 0 2 4 6 8 10 12 G ra H ss T W oo d W S U S O KE B PB Gasifier Recalcitrance? EB PC E B Hydrothermal Fast Pyrolysis Slow Pyrolysis PC N C S1 PN C N S2 L- M (M P) PN PN N N L- L- P S (S G ) O AK W A L H W W S O K C SB O ak
  14. 14. Modeled half-life (yr) of biochars prepared at different temperatures from various feedstocks Feedstock 250°C 400°C 525°C 650°C Oak 840 1020 9590 96200 Pine -- 990 6790 17000 Cedar 730 23800 12800 20000000 Bubinga 1200 4300 -- 15600 Gamma 260 370 930 -- Grass Sugar Cane 690 9310 2280 146600 Zimmerman, 2010 EST online Amonette 04Mar2010
  15. 15. Estimated half-life in soils: effect of temperature Estimates of Half-life in Soils (Slow Pyrolysis Biochars) 1400 Cheng et al. (2008) 1200 Kuzyakov et al. (2009) 1000 Time, years 800 600 400 200 0 5 10 15 20 25 30 35 Mean Annual Temp, C Amonette 04Mar2010
  16. 16. Surface Chemistry Slow Fast Gas Slow Pyrolysis chars produced in presence of steam at 475°C tend to be acidic (carboxylic acid groups activated) Fast Pyrolysis chars produced in absence of steam at 500°C tend to be slightly basic Gasification chars produced in presence of steam at 700°C tend to be very basic and make good liming agents Amonette 04Mar2010
  17. 17. Surface Chemistry—Boehm titration results 1200 NaOH Analyte Slow Pyrolysis (steam) Na2CO3 Analyte 1000 NaHCO3 Analyte Fast Pyrolysis (no steam) HCl Analyte 800 Gasification (steam)  600 400 200 0 OKEB PBEB PCEB PCN OAK PNNL‐M PNNL‐P PNNL‐S HW OK (CSA)  WS  CSB  ‐200 Amonette 04Mar2010
  18. 18. Inferred pH-Dependent Exchange Capacities Oak Feedstock 1000 OKEB Slow Pyrolysis (steam), 475°C 800 OAK Ion Sorption Capacity, meq/kg OK (CSA) Cations 600 400 Fast Pyrolysis, 500°C 200 Gasification (steam), 700°C 0 0 2 4 6 8 10 12 14 Anions -200 -400 -600 pH Amonette 04Mar2010
  19. 19. Hydrophilicity 75 Hydrothermal 70 Slow Pyrolysis Fast Pyrolysis 65 -1 Gasifier Surface Tension, mN m Increasing Hydrophilicity 60 55 50 45 40 35 30 PN ) P B ) EB B P SB S d K ak W S1 S2 AK S G L ss L- E KE oo (M O W A (S U H O PC PB ra C C C N W O W S O M G S W L- L- N N PN PN Amonette 04Mar2010 “Molarity of ethanol drop” method
  20. 20. Speculations on the best biochar type for soil application Criteria Near-neutral pH High ion exchange capacities (CEC and AEC) Moderate hydrophobicity to retain organics High stability to oxidation Low volatile content Pre-treated with NH4+ to avoid induced N deficiency Recommendation Steam-activated Carbonized (i.e., treated to higher temperature to remove volatiles) Slow pyrolysis probably better If none of above, best to let biochar age weeks to months (compost?) before adding to soil, unless being used to lime Amonette 04Mar2010
  21. 21. Acknowledgments Thanks to Stefan Czernik, Danny Day, Bob Hawkins, Hal Collins, Manuel Garcia-Perez, Doug Elliott, Marcus Antonietti, Emma Suddick, and Michael Antal for samples of biochars analyzed here Research supported by USDOE Office of Fossil Energy through the National Energy Technology Laboratory USDOE Office of Biological and Environmental Research (OBER) through the Carbon Sequestration in Terrestrial Ecosystems (CSiTE) project. Research was performed at the W.R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility at the Pacific Northwest National Laboratory (PNNL) sponsored by the USDOE-OBER. PNNL is operated for the USDOE by Battelle Memorial Institute under contract DE AC06 76RL01830. Amonette 04Mar2010

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