Chemical Papers

, Volume 63, Issue 1, pp 15–25 | Cite as

Integration of biomass drying with combustion/gasification technologies and minimization of emissions of organic compounds

  • Karel Svoboda
  • Jiří Martinec
  • Michael Pohořelý
  • David Baxter


Moisture content (MC) of green biomass or raw biomass materials (wood, bark, plants, etc.) commonly exceeds 50 mass % (wet basis). The maximum possible MC of biomass fuel for big scale combustion (e.g. fluidized bed combustion with low external heat losses) is approximately 60–65 mass %. Higher biomass MC generally causes operational problems of biomass combustors, lower stability of burning and higher CO and VOC emissions. Gasification of biomass with higher MC produces fuel gas of lower effective heating values and higher tar concentrations. In this review, various technological schemes for wood drying in combination with combustion/gasification with the assessment of factors for possible minimization of emissions of organics from the drying processes are compared. The simple direct flue gas biomass drying technologies lead to exhaust drying gases containing high VOC emissions (terpenes, alcohols, organic acids, etc.). VOC emissions depend on the drying temperature, residence time and final MC of the dried biomass. Indirect biomass drying has an advantage in the possibility of reaching very low emissions of organic compounds from the drying process. Exhaust drying gases can be simply destroyed as a part of the total combustion air (gas) in a combustion chamber or a gasifier. Liquid, condensed effluents have to be treated properly because they have relatively high content of organic compounds, some of them accompanied by odor. Drying of biomass with superheated steam offers more uniform drying of both small and bigger particles and shorter periods of higher temperatures of the dried biomass, particularly if drying to the final MC below 15 mass % is required. In practical modern drying technologies, biomass (mainly wood) is dried in recirculated gas of relatively high humidity (approaching saturation) and the period of constant rate drying is longer. Drying of moist wood material (saw dust, chips, etc.) is required in wood pellet production. Emissions of organics in drying depend on biomass properties, content of resins, storing time and on operational aspects of the drying process: drying temperature, drying medium, final MC, residence time, and particle size distribution of the dried biomass (wood). Integration of biomass drying with combustion/gasification processes includes the choice of the drying medium (flue gas, air, superheated steam). Properties of the drying media and operational parameters are strongly dependent on local conditions, fuel input of the combustion/gasification unit, cleaning of the exhaust drying media (gas, steam, wastewater), and on environmental factors and requirements.


wood drying combustion emissions VOC terpene 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Arshadi, M., & Gref, R. (2005). Emission of volatile organic compounds from softwood pellets during storage. Forest Products Journal, 55(12), 132–135.Google Scholar
  2. Banerjee, S., Su, W., Wild, M. P., Otwell, L. P., Hittmeier, M. E., & Nichols, K.M. (1998). Wet line extension reduces VOCs from softwood drying. Environmental Science & Technology, 32, 1303–1307. DOI: 10.1021/es970849o.CrossRefGoogle Scholar
  3. Bengtsson, P. (2004). The release of hydrocarbon from softwood drying: Measurement and modeling. Maderas. Ciencia y Tecnologia, 6, 109–122.Google Scholar
  4. Berghel, J., & Renström, R. (2002). Basic design criteria and corresponding results performance of a pilot-scale fluidized superheated atmospheric condition steam dryer. Biomass and Bioenergy, 23, 103–112. DOI: 10.1016/S0961-9534(02)00040-5.CrossRefGoogle Scholar
  5. Bhattacharya, S. C., Albina, D. O., & Khaing, A. M. (2002). Effects of selected parameters on performance and emission of biomass-fired cook-stoves. Biomass and Bioenergy, 23, 387–395. DOI: 10.1016/S0961-9534(02)00062-4.CrossRefGoogle Scholar
  6. Björk, H., & Rasmuson, A. (1995). Moisture equilibrium of wood and bark chips in superheated steam. Fuel, 74, 1887–1890. DOI: 10.1016/0016-2361(95)80024-C.CrossRefGoogle Scholar
  7. Björk, H., & Rasmuson, A. (1996). Formation of organic compounds in superheated steam dying of bark chips. Fuel, 75, 81–84. DOI: 10.1016/0016-2361(95)00154-9.CrossRefGoogle Scholar
  8. Brammer, J. G., & Bridgewater, A. V. (1999). Drying technologies for an integrated gasification bio-energy plant. Renewable and Sustainable Energy Reviews, 3, 243–289. DOI: 10.1016/S1364-0321(99)00008-8.CrossRefGoogle Scholar
  9. Brammer, J. G., & Bridgewater, A. V. (2002). The influence of feedstock drying on the performance and economics of a biomass gasifier-engine CHP system. Biomass and Bioenergy, 22, 271–281. DOI: 10.1016/S0961-9534(02)00003-X.CrossRefGoogle Scholar
  10. Danielsson, S., & Rasmuson, A. (2002). The influence of drying medium, temperature, and time on the release of monoterpenes during convective drying of wood chips. Drying Technology, 20, 1427–1444. DOI: 10.1081/DRT-120005860.CrossRefGoogle Scholar
  11. Fagernäs, L. (1993). Formation and behaviour of organic compounds in biomass dryers. Bioresource Technology, 46, 71–76. DOI: 10.1016/0960-8524(93)90056-H.CrossRefGoogle Scholar
  12. Fagernäs, L., & Sipilä, K. (1996). Emissions from biomass drying. In A. V. Bridgwater & D. G. B. Boocock (Eds.), Proceedings of the International Conference on Developments in Thermochemical Biomass Conversion, 20–24 May, 1996 (p. 15). Banff, Canada.Google Scholar
  13. Fang, M. X., Shen, D. K., Li, Y. X., Yu, C. J., Luo, Z. Y., & Cen, K. F. (2006). Kinetic study on pyrolysis and combustion of wood under different oxygen concentrations by using TGFTIR analysis. Journal of Analytical and Applied Pyrolysis, 77, 22–27. DOI: 10.1016/j.jaap.2005.12.010.CrossRefGoogle Scholar
  14. Fitzpatrick, J. J., & Lynch, D. (1995). Thermodynamic analysis of the energy saving potential of superheated steam drying. Food and Bioproducts Processing: Transactions of the Institution of Chemical Engineers, 73, 3–8.Google Scholar
  15. Gómez, C. J., Mészáros, E., Jakab, E., Velo, E., & Puigjaner, L. (2007). Thermo-gravimetric/mass spectrometry study of woody residues and an herbaceous biomass crop using PCA techniques. Journal of Analytical and Applied Pyrolysis, 80, 416–456. DOI: 10.1016/j.jaap.2007.05.003.CrossRefGoogle Scholar
  16. Granström, K. (2003). Emissions of monoterpenes and VOCs during drying of sawdust in a spouted bed. Forest Products Journal, 53(10), 48–55.Google Scholar
  17. Gruber, T. (2001). Drying of wood chips with optimized energy consumption and emission levels, combined with production of valuable substances. In Proceedings of the 3rd European COST E15 Workshop on Wood Drying 2001, 11–13 June 2001. Helsinki, Finland.Google Scholar
  18. Holmberg, H., & Ahtila, P. (2004). Comparison of drying costs in biofuel drying between multi-stage and single-stage drying. Biomass and Bioenergy, 26, 515–530. DOI: 10.1016/j.biombioe.2003.09.007.CrossRefGoogle Scholar
  19. Ingram, L. L., Shmulsky, R., Dalton, A. T., Taylor, F. W., & Templeton, M. C. (2000). The measurement of volatile organic emissions from drying southern pine lumber in a laboratory-scale kiln. Forest Products Journal, 50(4), 91–94.Google Scholar
  20. Johansson, A., Fyhr, C., & Rasmuson, A. (1997). High temperature convective drying of wood chips with air and superheated steam. International Journal of Heat and Mass Transfer, 40, 2843–2858. DOI: 10.1016/S0017-9310(96)00341-9.CrossRefGoogle Scholar
  21. Johansson, L. S., Leckner, B., Gustavsson, L., Cooper, D., Tullin, C., & Potter, A. (2004). Emissions characteristics of modern and old-type residential boilers fired with wood logs and wood pellets. Atmospheric Environment, 38, 4183–4195. DOI: 10.1016/j.atmosenv.2004.04.020.CrossRefGoogle Scholar
  22. Lehtikangas, P. (2000). Storage effects on pelletized sawdust, logging residues and bark. Biomass and Bioenergy, 19, 287–293. DOI: 10.1016/S0961-9534(00)00046-5.CrossRefGoogle Scholar
  23. Lehtikangas, P. (2001). Quality properties of pelletized sawdust, logging residues and bark. Biomass and Bioenergy, 20, 351–360. DOI: 10.1016/S0961-9534(00)00092-1.CrossRefGoogle Scholar
  24. Makowski, M., Ohlmeyer M., & Meier, D. (2005). Long-term development of VOC emissions from OSB after hot-pressing. Holzforschung, 59, 519–523. DOI: 10.1515/HF.2005.086.CrossRefGoogle Scholar
  25. McIlveen-Wright, D. R., Williams, B. C., & McMullan, J. T. (2001). A re-appraisal of wood-fired combustion. Bioresource Technology, 76, 183–190. DOI: 10.1016/S0960-8524(00)001292.CrossRefGoogle Scholar
  26. Moreno, R., Antolín, G., Reyes, A., & Alvarez, P. (2004). Drying characteristics of forest biomass particles of Pinus radiate. Biosystems Engineering, 88, 105–115. DOI: 10.1016/j.biosystemseng.2004.02.005.CrossRefGoogle Scholar
  27. Olsson, M., & Kjällstrand, J. (2004). Emissions from burning of softwood pellets. Biomass and Bioenergy, 27, 607–611. DOI: 10.1016/j.biombioe.2003.08.018.CrossRefGoogle Scholar
  28. Otwell, L. P., Hittmeier, M. E., Hooda, U., Yan, H., Su, W., & Banerjee, S. (2000). HAPs release from wood drying. Environmental Science & Technology, 34, 2280–2283. DOI: 10.1021/es991083q.CrossRefGoogle Scholar
  29. Pakowski, Z., Krupinska, B., & Adamski, R. (2007). Prediction of sorption equilibrium both in air and superheated steam drying of energetic variety of willow (Salix viminalis) in a wide temperature range. Fuel, 86, 1749–1757. DOI: 10.1016/j.fuel.2007.01.016.CrossRefGoogle Scholar
  30. Prins, M. J., Ptasinski, K. J., & Janssen, F. J. J. G. (2006a). Torrefaction of wood, Part 1. Weight loss kinetics. Journal of Analytical and Applied Pyrolysis, 77, 28–34. DOI: 10.1016/j.jaap.2006.01.002.CrossRefGoogle Scholar
  31. Prins, M. J., Ptasinski, K. J., & Janssen, F. J. J. G. (2006b). Torrefaction of wood, Part 2. Analysis of products. Journal of Analytical and Applied Pyrolysis, 77, 35–40. DOI: 10.1016/j.jaap.2006.01.001.CrossRefGoogle Scholar
  32. Raghavan, G. S. V., Rennie, T. J., Sunjka, P. S., Orsat, V., Phaphuangwittayakul, W., & Terdtoon, P. (2005). Overview of new techniques for drying biological materials with emphasis on energy aspects. Brasilian Journal of Chemical Engineering, 22, 195–201. DOI: 10.1590/S0104-66322005000200005.Google Scholar
  33. Renström, R., & Berghel, J. (2002). Drying of sawdust in an atmospheric pressure spouted bed steam dryer. Drying Technology, 20, 449–464. DOI: 10.1081/DRT-120002551.CrossRefGoogle Scholar
  34. Renström, R., Lindquist, L., & Wikström, F. (2004). Study of the environmental impact of wood fuel processing. In Drying 2004 — Proceedings of the 14-th International Drying Symposium, 22–25 August, 2004, Vol. B (pp. 986–989). São Paulo, Brazil.Google Scholar
  35. Rhén, C., Gref, R., Sjöström, M., & Wästerlund, I. (2005). Effects of raw material moisture content, densification pressure and temperature on some properties of Norway spruce pellets. Fuel Processing Technology, 87, 11–16. DOI: 10.1016/j.fuproc.2005.03.003.CrossRefGoogle Scholar
  36. Rupar, K., & Sanati, M. (2003). The release of organic compounds during biomass drying upon the feedstock and/or altering drying heating medium. Biomass and Bioenergy, 25, 615–622. DOI: 10.1016/S0961-9534(03)00055-2.CrossRefGoogle Scholar
  37. Samuelsson, R., Nilsson, C., & Burvall, J. (2006). Sampling and GC-MS as a method for analysis of volatile organic compounds (VOC) emitted during oven drying of biomass materials. Biomass and Bioenergy, 30, 923–928. DOI: 10.1016/j.biombioe.2006.06.003.CrossRefGoogle Scholar
  38. Schuster, G., Löffler, G., Weigl, K., & Hofbauer, H. (2001). Biomass steam gasification — an extensive parametric modeling study. Bioresource Technology, 77, 71–79. DOI: 10.1016/S0960-8524(00)00115-2.CrossRefGoogle Scholar
  39. Spets, J. P., & Ahtila, P. (2002). Improving the power-to-heat ratio in CHP plants by means of a biofuel multistage drying system. Applied Thermal Engineering, 22, 1175–1180. DOI: 10.1016/S1359-4311(02)00045-5.CrossRefGoogle Scholar
  40. Spets, J. P., & Ahtila, P. (2004). Reduction of organic emissions by using a multistage drying system for wood-based biomasses. Drying Technology, 22, 541–561. DOI: 10.1081/DRT-120030000.CrossRefGoogle Scholar
  41. Stahl, M., Granström, K., Berghel, J., & Renström, R. (2004). Industrial processes for biomass drying and their effects on the quality properties of wood pellets. Biomass and Bioenergy, 27, 621–628. DOI: 10.1016/j.biombioe.2003.08.019.CrossRefGoogle Scholar
  42. Su, W., Yan, H., Banerjee, S., Otwell, L. P., & Hittmeier, M. E. (1999). Field-proven strategies for reducing volatile carbons from hardwood drying. Environmental Science & Technology, 33, 1056–1059. DOI: 10.1021/es980453s.CrossRefGoogle Scholar
  43. Tsujiyama, S., & Miyamori, A. (2000). Assignment of DSC thermograms of wood and its components. Thermochimica Acta, 351, 177–181. DOI: 10.1016/S0040-6031(00)00429-9.CrossRefGoogle Scholar
  44. van Deventer, H. C. (2004). Industrial superheated steam drying. TNO-report R 2004/239. Apeldoorn, The Netherlands: TNO Environment, Energy and Process Innovation. Google Scholar
  45. Vinterbäck, J. (2004). Pellets 2002: the first world conference on pellets. Biomass and Bioenergy, 27, 513–520. DOI: 10.1016/j.biombioe.2004.05.005.CrossRefGoogle Scholar
  46. Wimmerstedt, R. (1999). Recent advances in biofuel drying. Chemical Engineering and Processing, 38, 441–447. DOI: 10.1016/S0255-2701(99)00041-0.CrossRefGoogle Scholar

Copyright information

© Institute of Chemistry, Slovak Academy of Sciences 2008

Authors and Affiliations

  • Karel Svoboda
    • 1
  • Jiří Martinec
    • 2
  • Michael Pohořelý
    • 1
    • 3
  • David Baxter
    • 2
  1. 1.Institute of Chemical Process FundamentalsAcademy of Sciences of the Czech RepublicPragueCzech Republic
  2. 2.Cleaner Energies Unit, Institute for EnergyJRCPettenThe Netherlands
  3. 3.Department of Power EngineeringInstitute of Chemical TechnologyPragueCzech Republic

Personalised recommendations