Use of chemical and physical characteristics to investigate trends in biochar feedstocks   Fungai Mukome, Xiaoming Zhang, Lucas C.R. Silva, Johan Six, and Sanjai J. Parikh University of California, Davis US Biochar Conference, Rohnert Park, CA July 2012

What is Biochar? Walnut shell Wood chips Rice Husks Manure Corn stover Orange peels Fly ash carbon-negative.us Wood

All biochars are not created equal…. (McLaughlin et al. 2009) Differ on pH Surface area Ash content Water holding capacity Cation exchange capacity (CEC) H/C ratio C/N ratio The top 3 are usually proprietary Feedstock choice based on locally available resources – airborne loss, transportation costs and reduced carbon footprint All a function of pyrolysis temperature (highest treatment temperature-HTT), pyrolysis method, residence time and feedstock

Objectives To characterize physical and chemical properties of various biochars (mostly commercially available) To determine if trends exist for biochar properties that can be related to feedstock material, which can serve to develop guidelines for biochar use.

Objectives 1 Twelve biochars were analyzed Physical properties: Moisture content Ash content BET Surface area Surface morphology Chemical properties: Elemental content H and C content pH Cation exchange capacity Surface basicity and acidity Surface functionality (ATR-FTIR and Raman)

Physical properties Char Source Material Pyrolysis Temp (°C) Ash (wt %) BET Surface Area (m2/g) Type (Hysteresis) BC_ A Turkey litter 700-800 64 21.8 aPs. II (H3) BC_Bb Walnut shell 900 40.4 227.1 Ps. II (H4) BC_C Inoculated material unavailablec 15.5 95.9 BC_D Soft wood 600-700 2.4 25.2 BC_E Wood + Algal digestate 6.4 2 Ps. II (H3) BC_F Wood 510 3 165.8 BC_G 410 2.6 2.8 BC_H Wood chips 500-650 17 4.9 BC_I unavailable 5 164.1 BC_J 153.1 BC_K 5.5 154.4 BC_L 4.2 301.6 Separate into a Ps.II = Pseudo Type II b Unknown, not willing to provide or proprietary c Not commercially available Wood Non-wood

Scanning Electron Microscopy analysis SEM images of three biochars showing a) a char with type H3 hysteresis loop b) a char with type H4 hysteresis loop and c) a char with high ash content. c) BC_B a) BC_G b) BC_F 10µm 100µm 60µm Type II isotherms - capillary non-porous or macroporous adsorbents and represent monolayer-multilayer adsorption. Lower surface areas (BC_J,BC_H, BC_A and BC_G) - Type H3 hysteresis loops - lack of microporosity, plate-like particles and slit shaped pores. Higher surface area - (BC_L, BC_K, BC_J, BC_I, BC_F) - Type H4 hysteresis loops- narrow slit-like pores

Chemical properties aCEC = Cation exchange capacity Char C (wt %) N (wt %) H (wt %) O (wt %) PO4-P (wt %) K (wt %) S (ppm) Fe (ppm) pHw (1:2) CECa cmol/kg Acidity (meq/g) Basicity (meq/g) BC_A 15.6 0.78 0.83 4.4 6.61 7.05 10720 9191 10.9 24.4 0.08 4.92 BC_Bb 55.3 0.47 0.89 1.6 0.64 9.32 940 1981 9.7 33.4 - 11.71 BC_C 53.3 1.96 3.7 24.3 1.2 5920 1109 6.8 44.5 1.22 1 BC_D 68.2 0.51 3.66 26.8 0.13 0.26 370 1934 7.5 26.2 1.24 1.02 BC_E 58.1 0.41 4.16 31.7 0.19 685 3370 67 1.56 BC_F 83.9 0.36 1.88 19.8 0.02 110 505 7.3 12 0.27 0.93 BC_G 65.7 0.21 4.38 23.5 0.12 50 248 7.1 10 0.4 BC_H 71.2 0.91 2.88 11.6 0.72 480 3517 7.9 3.2 0.79 1.01 BC_I 87.3 0.59 2.15 7.4 0.07 0.85 140 203 9.2 9.1 0.84 BC_J 88 0.44 2.55 14.8 0.33 60 79 9.5 14.9 0.49 0.87 BC_K 85.4 0.55 2.37 8.9 0.48 606 8.8 3.6 0.6 0.94 BC_L 82.5 1.64 5.6 0.06 160 473 16.5 1.21 High C in wood derived biochar aCEC = Cation exchange capacity b Not commercially available Wood Non-wood

Greater aromaticity in wood derived biochar FTIR: Fourier Transform Infrared Spectroscopy Aromatic C=C C-H Aliphatic/Functionalized C-O, C-H C-O C=O Greater aromaticity in wood derived biochar

xAliphatic ether (1029cm-1) xAromatic carbonyl (1690cm-1) Char xAromatic C-H (744cm-1) xAliphatic ether (1029cm-1) xAliphatic CH3 (1417cm-1) xAromatic C=C (1587cm-1) xAromatic carbonyl (1690cm-1) BC_A - 2.9 1 0.21 0.02 BC_B 1.1 2.2 BC_C 0.53 3.6 0.38 0.69 0.39 BC_D 0.63 2.67 2.46 2.6 1.2 BC_E 0.27 2.83 2.05 0.94 BC_F 2.09 1.7 2.3 0.28 BC_G 2.16 0.83 1.5 0.4 BC_H 1.12 1.71 1.78 0.41 BC_I 1.83 1.98 BC_J 0.71 1.67 1.41 0.36 BC_K 1.05 1.17 1.6 1.9 BC_L 1.01 1.22 0.12 x. Ratios of peak intensities relative to the aromatic C-H stretch at 870cm-1 common to all spectra

ID - sp2 disordered C atoms in aromatic ring structures Char Aliphatic ether (1029cm-1) yRaman Id/Ig BC_A 2.9 0.4 BC_B 1.1 0.34 BC_C 3.6 0.76 BC_D 2.67 0.58 BC_E 2.83 0.65 BC_F 2.09 BC_G 2.16 0.25 BC_H 1 0.83 BC_I 1.2 0.68 BC_J 1.67 0.72 BC_K 1.17 0.59 BC_L 1.01 0.71 y. Ratio of peak intensities of the Carbon D (1350cm-1) and G (1690cm-1) bands in Raman spectra ID - sp2 disordered C atoms in aromatic ring structures IG - sp2 disordered C atoms in aliphatic and olefinic molecules Approximates sp2: sp3 ratio in amorphous carbon D band (aromatic) G band (aliphatic & olefinic)

Objective 2 van Krevelen diagram of a) selected biochar (from literature) and b) 12 study biochar (inset) 1. Sharma et al. Fuel 2004, 83, 1469-1482. 2. Keiluweit et al. Environmental Science & Technology 2010, 44, 1247-1253. 3. Zheng et al. Journal of Hazardous Materials 2010, 181, 121-126. 4. Cao, X. et al. Bioresource Technology 2010, 101, 5222-5228. 5. Özçimen et al. Renewable Energy 2010, 35, 1319-1324. 6. Jindarom et al. Chemical Engineering Journal 2007, 133, 239-246. 7. Chan et al. Soil Research 2008, 46, 437-444. 8. Azargohar et al. Applied Biochemistry and Biotechnology 2006, 131, 762-773. 9. Wu et al. Industrial & Engineering Chemistry Research 2009, 48, 10431-10438. 10. Toles et al. Bioresource Technology 2000, 71, 87-92. 11. Van Zwieten et al. Plant and Soil 2010, 327, 235-246. 12. Chen, B. and Chen, Z. Chemosphere 2009, 76, 127-133. 13. Major et al. Plant and Soil 2010, 333, 117-128. 14. Argudo, M. et al. Carbon 1998, 36, 1027-1031. 15. Hammes et al. Applied Geochemistry 2008, 23, 2113-2122. 16. Chun et al. Environmental Science & Technology 2004, 38, 4649-4655. 17. Mahinpey et al. Energy & Fuels 2009, 23, 2736-2742. 18. Rondon et al. Biology and Fertility of Soils 2007, 43, 699-708. 19. Abdullah, H. and Wu, H. Energy & Fuels 2009, 23, 4174-4181. 20. Cheng, C.-H and Lehmann, J. Chemosphere 2009, 75, 1021-1027. 21. Spokas et al. Chemosphere 2009, 77, 574-581. 22. Steiner et al. J. Environ. Qual. 2009, 39, 1236-1242. 23. Busscher et al. Soil Science 2010, 175, 10-14. 24. Brewer et al. Environmental Progress & Sustainable Energy 2009, 28, 386-396. 25. Novak et al. Annals of Environmental Science 2009, 3, 195-206. 26. Novak, J. M. and Reicosky, D. C. Annals of Environmental Science 2009, 3, 179-193. 27. Singh et al. J. Environ. Qual. 2010, 39, 1224-1235. A algae G grass L hull M manure N nutshell P pomace W wood Challenges n= 85

Change in ash content as a function of pyrolysis temperature of biochar Change in ash content as a function of pyrolysis temperature of biochar derived from hard and softwood Wood material has lower ash content Greater ash content in hard wood compared to softwood

Change in the C/N ratio as a function of pyrolysis temperature of biochar Change in the C/N ratio as a function of pyrolysis temperature of biochar derived from hard and softwood.

Change in the surface area as a function of pyrolysis temperature of biochar Change in surface area as a function of pyrolysis temperature of biochar derived from hard and softwood

Box plots showing differences in a) ash content and b) C/N ratios, but not in c) surface area across the different feedstocks. The grey boxes show the range from first to third quartiles, with the median dividing the interquartile range, into two boxes for the second and third quartiles. Letters show significant differences (p<0.05) according to a one-way ANOVA followed by Tukey (HSD) multiple means comparison

Suggested guidelines Property Agroecosystem consideration Ash content Hydrophobicity and retention of agrochemicals C/N ratio Initial Immobilization of soil N Surface area Sorption of pesticides, herbicides and heavy metals, sites for fungal and microbial colonization Characteristic Suggested guideline Ash content grass ≈ manure >> nut shells, pomace and wood (hard wood > soft wood) C/N ratio wood >> grass> pomace> manure (soft wood > hard wood) Surface area temperature dependent

Acknowledgements Xiaoming Zhang Lucas C.R. Silva Johan Six Sanjai J. Parikh UC Davis Agricultural Sustainability Institute (ASI) Junior Faculty Award David and Lucile Packard Foundation Email:fmukome@ucdavis.edu

Effects of biochar Improves However many other studies have shown water holding capacity nutrient retention soil fertility agricultural yield greenhouse emission (GHG) mitigation However many other studies have shown no increase in crop yields, increased GHG emissions, unintended “liming” of soils. Results often linked to the properties of the biochar used, application rate, soil type and climate.