A pirólise da biomassa pode contribuir de duas formas para a mitigação do aquecimento global: pela estabilização de parte do C da biomassa na forma de carvão e pela produção de bio-óleo, que pode substituir os combustíveis fósseis como matéria prima para produção de energia e outros derivados (Basu, 2010).
Descontando-se da quantidade de C da biomassa recuperado no carvão (Figura 7), a quantidade de C lábil pelo método WB (Figura 18), estima-se que a pirólise da madeira a 400 °C proporciona a estabilização de maior quantidade de C, cerca de 51 %
45 do C da biomassa (Figura 19). Com a redução do rendimento gravimétrico de carvão com o aumento da TP, ocorre a redução da quantidade de C estabilizada, principalmente com nas maiores TA. Tendo que o maior rendimento de bio-óleo para a TA5 também foi obtida na TP de 400 °C, (Figura 3) esta é a temperatura de operação que permite a maior estabilização do C para esta TA. Para as TA22,5 e TA40, o maior rendimento de bio-óleo ocorrendo na TP de 450 °C coincide com uma pequena redução (cerca de 2 %) na quantidade de C estabilizada na forma de carvão. Esta pequena redução, no entanto, deve ser compensada pelo aumento do rendimento de bio-óleo com o aumento da TP de 400 para 450 °C, que foi de 6,3 % na TA22,5, e de 21,5 % na TA40.
O incremento da estabilidade térmica do carvão com o aumento da TP em que é produzido, também tem de ser considerada. Um maior valor da TUE pode ser interpretado como um aumento da energia de ativação necessária para promover a quebra das ligações químicas de um composto. Portanto, o aumento da TUE provavelmente deve implicar num maior tempo em que o C é mantido na forma estabilizada.
Figura 19. Quantidade de C recuperada nos carvões e recalcitrante ao Walkley–Black em função da temperatura de pirólise e taxa de aquecimento.
0 15 30 45 60 250 350 450 550 650 750 % Temperatura de pirólise (°C) TA5 TA22,5 TA40 madeira
46 5 CONCLUSÕES
A máxima produção de bio-óleo é obtida em temperaturas acima de 400 °C para a taxa de aquecimento de 5 °C/min, e acima de 450 °C para as taxas de aquecimento de 22,5 e 40 °C/min. O uso de maior taxa de aquecimento permitiu um aumento de até 7 % na conversão da madeira em bio-óleo;
Com o aumento da taxa de aquecimento, ocorre maior ruptura da estrutura do carvão, reduzindo a sua resistência física;
A redução da recuperação de nutrientes no carvão está associada à perda de massa durante a pirólise. Com exceção ao K, ocorre a redução da fração do teor total de nutrientes no carvão extraível em meio ácido;
A pirólise incompleta em temperaturas abaixo de 400 °C, apesar da maior recuperação do C da madeira no carvão, não contribui para a estabilização do C. Com o aumento da temperatura de pirólise acima de 400 °C, aumenta-se a estabilidade térmica dos carvões e a recalcitrância do C ao método Walkley– Black;
A temperatura em que é realizada a pirólise exerce maior influência sobre as propriedades químicas e físicas do carvão do que a taxa de aquecimento.
47 6 REFERRÊNCIAS BIBLIOGRÁFICAS
ADGER, W.N.; AGRAWALA, S.; MIRZA, M.M.Q.; CONDE, C.; O’BRIEN, K.; PULHIN, J.; PULWARTY, R.; SMIT, B. & TAKAHASHI, K. Assessment of adaptation practices, options, constraints and capacity. In: PARRY, M.L.; CANZIANI, O.F.; PALUTIKOF, J.P.; VAN DER LINDEN, P.J. & HANSON, C.E., eds. Climate change 2007: impacts, adaptation and vulnerability. Contribution of working group II to the fourth assessment report of the intergovernmental panel on climate change. Cambridge, Cambridge University Press, 2007.
ANDEREGG, W.R.L.; PRALL, J.W.; HAROLD, J. & SCHNEIDER, S.H. Expert credibility in climate change. Proc. Natl. Acad. Sci. USA, 107:12107-12109, 2010.
ANTAL, M.J. & GRØNLI, M. The art, science, and technology of charcoal production. Ind. Eng. Chem. Res., 42:1619-1640, 2003.
ASCOUGH, P.L.; BIRD, M.I.; FRANCIS, S.M.; THORNTON, B.; MIDWOOD, A.J.; SCOTT, A.C. & APPERLEY, D. Variability in oxidative degradation of charcoal: Influence of production conditions and environmental exposure. Geochim. Cosmochim. Acta, 75:2361-2378, 2011.
ATKINSON, C.J.; FITZGERALD, J.D. & HIPPS, N.A. Potential mechanisms for achieving agricultural benefits from biochar application to temperate soils: a review. Plant Soil, 337:1-18, 2010.
BARCELLOS, D.C. Caracterização do carvão vegetal através do uso de espectroscopia no infravermelho próximo. 2007. 140f. Tese (Doutorado em Ciência Florestal) - Universidade Federal de Viçosa, Viçosa, 2007.
BASU, P. Biomass gasification and pyrolysis: practical design and theory. Burlington, Academic Press, 2010. 365p.
BIRD, M.I.; MOYO, C.; VEENDAAL, E.M.; LLOYD, J. & FROST, P. Stability of elemental carbon in a savanna soil. Glob. Biogeochem. Cycles, 13:923-932, 1999. BOEHM, H.-P. Surface chemical characterization of carbons from adsorption studies.
In: BOTTANI, E.J. & TASCÓN, J.M.D., eds. Adsorption by carbons. Amsterdam, Elsevier, 2008. p.301-328.
BOEHM, H.-P. Surface oxides on carbon and their analysis: a critical assessment. Carbon, 40:145-149, 2002.
48 BRODOWSKI, S.; JOHN, B.; FLESSA, H. & AMELUNG, W. Aggregate-occluded
black carbon in soil. Eur. J. Soil Sci., 57:539-546, 2006.
BROWN, R.A.; KERCHER, A.K.; NGUYEN, T.H.; NAGLE, D.C. & BALL, W.P. Production and characterization of synthetic wood chars for use as surrogates for natural sorbents. Org. Geochem., 37:321-333, 2006.
BRUUN, S.; JENSEN, E.S. & JENSEN, L.S. Microbial mineralization and assimilation of black carbon: dependency on degree of thermal alteration. Org. Geochem., 39:839-845, 2008.
BRUUN, E.W.; HAUGGAARD-NIELSEN, H.; IBRAHIM, N.; EGSGAARD, H.; AMBUS, P.; JENSEN, P.A. & DAM-JOHANSEN, K. Influence of fast pyrolysis temperature on biochar labile fraction and short-term carbon loss in a loamy soil. Biomass Bioenergy, 35:1182-1189, 2011.
BYRNE, C.E. & NAGLE, D.C. Carbonized wood monoliths - characterization. Carbon, 35:267-273, 1997.
CHAN, K.Y. & XU, Z. Biochar: Nutrient properties and their enhancement. In: Lehmann, J. & Joseph, S., eds. Biochar for environmental management: science and technology. Londres, Earthscan, 2009. p.67-84.
CHENG, C.-H.; LEHMANN, J.; THIES, J.E.; BURTON, S.D. & ENGELHARD, M.H. Oxidation of black carbon by biotic and abiotic processes. Org. Geochem., 37:1477-1488, 2006.
CUÑA SUÁREZ, A.; TANCREDI, N.; PINHEIRO, P.C.C. & YOSHIDA, M.I. Thermal analysis of the combustion of charcoals from Eucalyptus dunnii obtained at different pyrolysis temperatures. J. Therm. Anal. Calorim., 100:1051-1054, 2010.
DEMIRBAS, M.F. Biorefineries for biofuel upgrading: A critical review. Applied Energy, 86:S151-S161, 2009.
EL-HENDAWY, A.A. Surface and adsorptive properties of carbons prepared from biomass. Appl. Surf. Sci., 252:287-295, 2005.
FAHMI, R.; BRIDGWATER, A.V.; DARVELL, L.I.; JONES, J.M.; YATES, N.; THAIN, S. & DONNISON, I.S. The efect of alkali metals on combustion and pyrolysis of Lolium and Festuca grasses, switchgrass and willow. Fuel, 86:1560- 1569, 2007.
49 FIGUEIREDO, J.L.; PEREIRA, M.F.R.; FREITAS, M.M.A. & ÓRFÃO, J.J.M.
Modification of the surface chemistry of activated carbons. Carbon, 37:1379- 1389, 1999.
FORBES, M.S.; RAISON, R.J. & SKJEMSTAD, J.O. Formation, transformation and transport of black carbon (charcoal) in terrestrial and aquatic ecosystems. Sci. Tot. Environ., 370:190-206, 2006.
GARCIA-PEREZ, M.; WANG, S.; SHEN, J.; RHODES, M.J.; LEE, W.-J. & LI, C.-Z. Effects of temperature on the formation of lignin-derived oligomers during the fast pyrolysis of Mallee woody biomass. Energy Fuels, 22:2022-2032, 2008a. GARCIA-PEREZ, M.; WANG, X.S.; SHEN, J.; RHODES, M.J.; TIAN, F.; LEE, W.-J.;
WU, H. & LI, C.-Z. Fast pyrolysis of oil mallee woody biomass: Effect of temperature on the yield and quality of pyrolysis products. Ind. Eng. Chem. Res., 47:1846-1854, 2008b.
GLASER, B.; HAUMAIER, L.; GUGGENBERGER, G. & ZECH, W. The ‘Terra Preta’ phenomenon - a model for sustainable agriculture in the humid tropics. Naturwissenschaften, 88:37-41, 2001.
GLASER, B.; LEHMANN, J. & ZECH, W. Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoal - a review. Biol. Fertil. Soils 35:219-230, 2002.
GOMIDE, J.L. & COLODETTE, J.L. Qualidade da madeira. In: BORÉM, A., ed. Biotecnologia florestal. Viçosa, Editora UFV, 2007. p.25-54.
GUNDALE, M.J. & DELUCA, T.H. Charcoal effects on soil solution chemistry and growth of Koeleria macrantha in the ponderosa pine/Douglas-fir ecosystem, Biol. Fertil. Soils, 43:303-311, 2007.
HAMMES, K.; TORN, M.S.; LAPENAS, A.G. & SCHMIDT, M.W.I. Centennial black carbon turnover observed in a Russian steppe soil. Biogeosciences Discussion, 5:661-683, 2008.
KEILUWEIT, M.; NICO, P.S.; JOHNSON, M. & KLEBER, M. Dynamic molecular structure of plant biomass-derived black carbon (biochar). Environ. Sci. Technol., 44:1247-1253, 2010.
KINTISCH, E. Report backsmore projects to sequester CO2 from coal. Science, 315:1481, 2007.
50 KUHLBUSCH, T.A.J. & CRUTZEN, P.J. Toward a global estimate of black carbon in residues of vegetation fires representing a sink of atmospheric CO2 and a source of O2. Glob. Biogeochem. Cycles, 9:491-501, 1995.
LEHMANN, J. & JOSEPH, S. Biochar for environmental management: an introduction. In: LEHMANN, J. & JOSEPH, S., eds. Biochar for environmental management: science and technology. London, Earthscan, 2009. p.1-12.
LEHMANN, J.; GAUNT, J. & RONDON, M. Bio-char sequestration in terrestrial ecosystems - a review. Mit. Adap. Strat. Glob. Chan., 11: 403-427, 2006.
LEHMANN, J.; SILVA JR., J.P.; STEINER, C.; NEHLS, T.; ZECH, W. & GLASER, B. Nutrient availability and leaching in an archaeological Anthrosol and a Ferralsol of the Central Amazon basin: Fertilizer, manure and charcoal amendments. Plant Soil, 249:343-357, 2003.
LEHMANN, J.; SKJEMSTAD, J.O.; SOHI, S.; CARTER, J.; BARSON, M.; FALLOON, P.; COLEMAN, K.; WOODBURY, P. & KRULL, E. Australian climate-carbon cycle feedback reduced by soil black carbon. Nature Geoscience, 1:832-835, 2008.
LEIFELD, J. Thermal stability of black carbon characterised by oxidative differential scanning calorimetry. Org. Geochem., 38:112-127, 2007.
LIANG, B.; LEHMANN, J.; SOLOMON, D.; KINYANGI, J.; GROSSMAN, J.; O’NEILL, B.; SKJEMSTAD, J.O.; THIES, J.; LUIZÃO, F.J.; PETERSEN, J. & NEVES, E.G. Black carbon increases cation exchange capacity in soils. Soil Sci. Soc. Am. J., 70:1719-1730, 2006.
LIANG, B.; LEHMANN, J.; SOLOMON, D.; SOHI, S.; THIES, J.E.; SKJEMSTAD, J.O.; LUIZÃO, F.J.; ENGELHARD, M.H.; NEVES, E.G. & WIRICK, S. Stability of biomass-derived black carbon in soils. Geochim. Cosmochim. Acta, 72:6069- 6078, 2008.
LIMA, H.N.; SCHAEFER, C.E.R.; MELLO, J.W.V.; GILKES, R.J. & KER, J.C. Pedogenesis and pre-Colombian land use of “Terra Preta Anthrosols” (“Indian black earth”) of Western Amazonia. Geoderma, 110:1-17, 2002.
MASIELLO, C.A. & DRUFFEL, E.R.M. Black carbon in deep-sea sediments. Science, 280:1911-1913, 1998.
MENDONÇA, E.S. & MATOS, E.S. Matéria orgânica do solo: métodos de análise. Viçosa, Editora UFV, 2005. 107p.
51 MOHAN, D.; PITTMAN JR., C.U. & STEELE, P.H. Pyrolysis of wood/biomass for
bio-oil:? a critical review. Energy Fuels, 20:848-889, 2006.
MORIARTY, P. & HONNERY, D. Rise and fall of the carbon civilisation - resolving global environmental and resource problems. London, Springer-Verlag, 2011. MUKHERJEE, A.; ZIMMERMAN, A.R. & HARRIS, W. Surface chemistry variations
among a series of laboratory-produced biochars. Geoderma, 163:247-255, 2011. NGUYEN, B.T. & LEHMANN, J. Black carbon decomposition under varying water
regimes. Org. Geochem., 40:846-853, 2009.
NGUYEN, B.T.; LEHMANN, J.; KINYANGI, J.; SMERNIK, R.; RIHA, S.J. & ENGELHARD, M.H. Long-term dynamics of black carbon in cultivated soil. Biogeochemistry, 89:295-308, 2008.
OLIVEIRA, J. B.; VIERA FILHO, A.; MENDES, M. G.; GOMES, P. A. Produção de carvão vegetal: aspectos técnicos. In: Oliveira, J.B., ed. Produção e utilização de carvão vegetal. Belo Horizonte, CETEC, 1982. p.59-74.
ORESKES, N. The scientific consensus on climate change. Science, 306:1686, 2004. PASTOR-VILLEGAS, J.; MENESES RODRÍGUEZ, J.M.; PASTOR-VALLE, J.F. &
GARCÍA GARCÍA, M. Changes in commercial wood charcoals by thermal treatments. J. Anal. Appl. Pyrol., 80:507-514, 2007
PICCOLO, A. & MBAGWU J.S.C. Effects of different organic waste amendments on soil microaggregates stability and molecular sizes of humic substances. Plant Soil, 123:27-37, 1990.
PICCOLO, A.; PIETRAMELLARA, G. & MBAGWU, J.S.C. Effects of coal derived humic substances on water retention and structural stability of Mediterranean soils. Soil Use Manag., 12:209-213, 1996.
PLANTE, A.F.; FERNÁNDEZ, J.M. & LEIFELD, J. Application of thermal analysis techniques in soil science. Geoderma, 153:1-10, 2009.
PRESTON, C.M. & SCHMIDT, M.W.I. Black (pyrogenic) carbon: A synthesis of current knowledge and uncertainties with special consideration of boreal regions. Biogeosciences, 3:397-420, 2006.
RANZI, E.; CUOCI, A.; FARAVELLI, T.; FRASSOLDATI, A.; MIGLIAVACCA, G.; PIERUCCI, S. & SOMMARIVA, S. Chemical kinetics of biomass pyrolysis. Energy Fuels, 22:4292-4300, 2008.
REYNOLDS, M.P. Climate change and crop production. Wallingford, CABI, 2010. 292p.
52 ROWELL, R.M.; PETTERSEN, R.; HAN, J.S.; ROWELL, J.S. & TSHABALALA,
M.A. Cell wall chemistry. In: ROWELL., R.M., ed. Handbook of wood chemistry and wood composites. Boca Raton, CRC Press, 2005. p.35-74.
RUMPEL, C.; CHAPLOT, V.; PLANCHON, O.; BERNADOUX, J.; VALENTIN, C. & MARIOTTI, A. Preferential erosion of black carbon on steep slopes with slash and burn agriculture. Catena, 65:30-40, 2006.
SCHMIDT, M.W.I.; SKJEMSTAD, J.O.; GEHRT, E. & KOGEL-KNABNER, I. Charred organic carbon in German chernozemic soils. Eur. J. Soil Sci., 50:351- 365, 1999.
SHEN, J. WANG, X.-S. GARCIA-PEREZ, M. MOURANT, D. RHODES, M.J. & LI, C.-Z. Effects of particle size on the fast pyrolysis of oil mallee woody biomass. Fuel, 88:1810-1817, 2009.
SILBER, A.; LEVKOVITCH, I. & GRABER, E.R. pH-dependent mineral release and surface properties of cornstraw biochar: agronomic implications. Environ. Sci. Technol., 44:9318-9323, 2010.
SILVERSTEIN, R.M.; WEBSTER, F.X. & KIEMLE, D.J. Identificação espectrométrica de compostos orgânicos. 7.ed. Rio de Janeiro, LTC, 2007. 490p. SKJEMSTAD, J.O.; CLARKE, P.; TAYLOR, J.A.; OADES, J.M. & MCCLURE, S,G.
The chemistry and nature of protected carbon in soil. Aust. J. Soil Res., 34:251- 271, 1996.
SKJEMSTAD, J.O.; REICOSKY, D.C.; WILTS, A.R. & MCGOWAN, J.A. Charcoal carbon in US agricultural soils. Soil Sci. Soc. Am. J., 66:1249-1255, 2002.
SMITH, J.B.; SCHELLNHUBER, H.; MIRZA, M.Q.; FANKHAUSER, S.; LEEMANS, R.; ERDA, L.; OGALLO, L.; PITTOCK, B.; RICHELS, R.; ROSENZWEIG, C.; SAFRIEL, U.; TOL, R.S.J.; WEYANT, J.; & YOHE, G. Vulnerability to Climate Change and Reasons for Concern: A Synthesis. In: MCCARTHY, J.J.; CANZIANI, O.F.; LEARY, N.A.; DOKKEN, D.J. & WHITE, K.S., eds. Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, Cambridge University Press, 2001.
SMITH, S.V.; RENWICK, W.H.; BUDDENMEIER, R.W. & CROSSLAND, C.J. Budgets of soil erosion and deposition for sediments and sedimentary organic
53 carbon across the conterminous United States. Glob. Biogeochem. Cycles, 15:697-707, 1999.
STALLARD, R.W. Terrestrial sedimentation and the carbon cycle: coupling weathering and erosion to carbon burial. Glob. Biogeochem. Cycles, 12:231-257, 1998.
STEINER, C.; TEIXEIRA, W.G.; LEHMANN, J.; NEHLS, T.; MACÊDO, J.L.V.; BLUM, W.E.H. & ZECH, W. Long term effects of manure, charcoal and mineral fertilization on crop production and fertility on a highly weathered Central Amazonian upland soil. Plant Soil, 291:275-290, 2007.
SUTTON, D.; KELLEHER, B. & ROSS, J.R.H. Review of literature on catalysts for biomass gasification. Fuel Process. Technol., 73:155-173, 2001.
SWIFT, R.S. Sequestration of carbon by soil. Soil Science, 166:858-871, 2001.
TRUGILHO, P.F. Aplicação de algumas técnicas multivariadas na avaliação da qualidade da madeira e do carvão vegetal de Eucalyptus. 1995. 160f. Tese (Doutorado em Ciência Florestal) - Universidade Federal de Viçosa, Viçosa, 1995.
TSHABALALA, M.A. Surface characterization. In: ROWELL., R.M., ed. Handbook of wood chemistry and wood composites. Boca Raton, CRC Press, 2005. p. 187-211. TSOURIS, C.; AARON, D.S. & WILLIAMS, K.A. Is carbon capture and storage really
needed? Environ. Sci. Technol., 44:4042-4045, 2010.
van ZWIETEN, L.; KIMBER, S.; MORRIS, S.; CHAN, K.Y.; DOWNIE, A.; RUST, J.; JOSEPH, S.; & COWIE, A. Effects of biochar from slow pyrolysis of papermill waste on agronomic performance and soil fertility. Plant Soil, 327:235-246, 2010. WALKLEY, A. & BLACK, I.A. An examination of the Degtjareff method for
determining soil organic matter and a proposed modification of the chromic acid titration method. Soil Sci., 37:29-38, 1934.
WINANDY, J.E. & ROWELL, R.M. Chemistry of wood strength. In: ROWELL., R.M., ed. Handbook of wood chemistry and wood composites. Boca Raton, CRC Press, 2005. p.303-347.
WOOTEN, J.B. SEEMAN, J.I. & HAJALIGOL, M.R. Observation and Characterization of cellulose pyrolysis intermediates by 13C CPMAS NMR. A new mechanistic model. Energy Fuels, 18:1-15, 2004.
YANG, H.; YAN, R. CHEN, H.; LEE, D.H. & ZHENG, C. Characteristics of hemicellulose, cellulose and lignin pyrolysis. Fuel, 86:1781-1788, 2007.
54 YOEMANS, J.C. & BREMNER, J.M. A rapid and precise method for routine
determination of organic carbon in soil. Comm. Soil Sci. Plant Anal., 19:1467- 1476, 1988.
YOWELL, M.A. & FERRELL, J.K. Using carbon sequestration projects to off-set greenhouse gas emissions. Nat. Resour. Environ., 20:20-25, 2005.
YU, C.-J.; TANG, Y.-L.; FANG, M.-X.; LUO, Z.-Y. & CEN, K.-F. Experimental study on alkali emission during rice straw pyrolysis. Journal of Zhejiang University (Engineering Science), 39:1435-1444, 2005.
YUAN, J.-H.; XU, R.-K. & ZHANG, H. The forms of alkalis in the biochar produced from crop residues at different temperatures. Bioresource Technol., 102:3488- 3497, 2011.
ZHANG, T.; WALAWENDER, W.P.; FAN, L.T.; FAN, M.; DAUGAARD, D. & BROWN, R.C. Preparation of activated carbon from forest and agricultural residues through CO2 activation. Chem. Eng. J., 105:53-59, 2004.
ZHOU, J.-H.; SUI, Z.-J.; ZHU, J.; LI, P.; CHEN, D.; DAI, Y.-C. & YUAN, W.-K. Characterization of surface oxygen complexes on carbon nanofibers by TPD, XPS and FT-IR. Carbon, 45:785-796, 2007.
ZIMMERMAN, A.R. Abiotic and microbial oxidation of laboratory-produced black carbon (biochar). Environ. Sci. Technol., 44:1295-1301, 2010.