Crop Management Impacts Biofuel Quality: Influence of Switchgrass Harvest Time on Yield, Nitrogen and Ash of Fast Pyrolysis Products


Although upgrading bio-oil from fast pyrolysis of biomass is an attractive pathway for biofuel production, nitrogen (N) and mineral matter carried over from the feedstock to the bio-oil represents a serious contaminant in the process. Reducing the N and ash content of biomass feedstocks would improve process reliability and reduce production costs of pyrolytic biofuels. This study investigated: (1) How does switchgrass harvest date influence the yield, N concentration ([N]), and ash concentration of biomass and fast pyrolysis products? and (2) Is there a predictive relationship between [N] of switchgrass biomass and [N] of fast pyrolysis products? Switchgrass from five harvest dates and varying [N] from central Iowa were pyrolyzed using a free-fall reactor. Harvestable biomass peaked in August (8.6 Mg ha−1), dropping significantly by November (6.7 Mg ha−1, P = 0.0027). Production of bio-oil per unit area mirrored that of harvested biomass at each harvest date; however, bio-oil yield per unit dry biomass increased from 46.6 % to 56.7 % during the season (P = 0.0018). Allowing switchgrass to senesce lowered biomass [N] dramatically, by as much as 68 % from June to November (P < 0.0001). Concurrently, bio-oil [N] declined from 0.51 % in June to 0.17 % by November (P < 0.0001). Significant reductions in ash concentration were also observed in biomass and char. Finally, we show for the first time that the [N] of switchgrass biomass is a strong predictor of the [N] of bio-oil, char, and non-condensable gas with R 2 values of 0.89, 0.94, and 0.88, respectively.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6


  1. 1.

    Perlack RD, Wright LL, Turhollow AF, Graham RL, Stokes BJ, Erbach DC (2011) U.S. billion-ton update: biomass supply for a bioenergy and bioproducts industry. Oak Ridge National Laboratory, Oak Ridge

    Google Scholar 

  2. 2.

    EISA (2007) Energy Independence and Security Act of 2007. Public Law 110–140. 121 Stat. 1492. 19 Dec. 2007., vol 121

  3. 3.

    Somerville C, Youngs H, Taylor C, Davis SC, Long SP (2010) Feedstocks for lignocellulosic biofuels. Science 329:790–792

    PubMed  Article  CAS  Google Scholar 

  4. 4.

    Boateng AA, Hicks KB, Vogel KP (2006) Pyrolysis of switchgrass (Panicum virgatum) harvested at several stages of maturity. J Anal Appl Pyrolysis 75:55–64

    Article  CAS  Google Scholar 

  5. 5.

    Wright L, Turhollow A (2010) Switchgrass selection as a “model” bioenergy crop: a history of the process. Biomass Bioenergy 34:851–868

    Article  Google Scholar 

  6. 6.

    Boateng AA, Daugaard DE, Goldberg NM, Hicks KB (2007) Bench-scale fluidized-bed pyrolysis of switchgrass for bio-oil production. Ind Eng Chem Res 46:1891–1897

    Article  CAS  Google Scholar 

  7. 7.

    Mullen CA, Boateng AA (2008) Chemical composition of bio-oils produced by fast pyrolysis of two energy crops. Energy Fuel 22:2104–2109

    Article  CAS  Google Scholar 

  8. 8.

    Bridgwater AV (1994) Catalysis in thermal biomass conversion. Appl Catal A Gen 116:5–47

    Article  CAS  Google Scholar 

  9. 9.

    Bridgwater AV (1996) Production of high grade fuels and chemicals from catalytic pyrolysis of biomass. Catal Today 29:285–295

    Article  CAS  Google Scholar 

  10. 10.

    Czernik S, Bridgwater AV (2004) Overview of applications of biomass fast pyrolysis oil. Energy Fuel 18:590–598

    Article  CAS  Google Scholar 

  11. 11.

    Huber GW, Iborra S, Corma A (2006) Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering. Chem Rev 106:4044–4098

    PubMed  Article  CAS  Google Scholar 

  12. 12.

    Bridgwater AV, Meier D, Radlein D (1999) An overview of fast pyrolysis of biomass. Org Geochem 30:1479–1493

    Article  CAS  Google Scholar 

  13. 13.

    Mohan D, Pittman CU, Steele PH (2006) Pyrolysis of wood/biomass for bio-oil: a critical review. Energy Fuel 20:848–889

    Article  CAS  Google Scholar 

  14. 14.

    Brewer CE, Hu Y-Y, Shchmidt-Rohr K, Loynachan TE, Laird DA, Brown RC (2012) Extent of pyrolysis impacts on fast pyrolysis biochar properties. J Environ Qual. doi:10.2134/jeq2011.0118

  15. 15.

    Laird DA (2008) The charcoal vision: a win–win–win scenario for simultaneously producing bioenergy, permanently sequestering carbon, while improving soil and water quality. Agron J 100:178–181

    Article  Google Scholar 

  16. 16.

    Vanderbosch RH, Prins W (2011) Fast pyrolysis. In: Brown RC (ed) Thermochemical processing of biomass: conversion into fuels, chemicals, and power, 1st edn. Wiley, Ames, IA, pp 124–153

    Chapter  Google Scholar 

  17. 17.

    Laird DA, Fleming P, Davis DD, Horton R, Wang B, Karlen DL (2010) Impact of biochar amendments on the quality of a typical Midwestern agricultural soil. Geoderma 158:443–449

    Article  CAS  Google Scholar 

  18. 18.

    Fahmi R, Bridgwater AV, Darvell LI, Jones JM, Yates N, Thain S et al (2007) The effect of alkali metals on combustion and pyrolysis of Lolium and Festuca grasses, switchgrass and willow. Fuel 86:1560–1569

    Article  CAS  Google Scholar 

  19. 19.

    McKendry P (2002) Energy production from biomass (part 1): overview of biomass. Bioresour Technol 83:37–46

    PubMed  Article  CAS  Google Scholar 

  20. 20.

    Demirbas A (2004) Combustion characteristics of different biomass fuels. Prog Energy Combust Sci 30:219–230

    Article  CAS  Google Scholar 

  21. 21.

    Lewandowski I, Kicherer A (1997) Combustion quality of biomass: practical relevance and experiments to modify the biomass quality of Miscanthus x giganteus. Eur J Agron 6:163–177

    Article  Google Scholar 

  22. 22.

    Sanderson MA, Wolf DD (1995) Switchgrass biomass composition during morphological development in diverse environments. Crop Sci 35:1432–1438

    Article  Google Scholar 

  23. 23.

    Adler PR, Sanderson MA, Boateng AA, Weimer PJ, Jung H-JG (2006) Biomass yield and biofuel quality of switchgrass harvested in fall or spring. Agron J 98:1518–1525

    Article  CAS  Google Scholar 

  24. 24.

    Brown RC (2011) Introduction to thermochemical processing of biomass into fuels, chemicals, and power. In: Brown RC (ed) Thermochemical processing of biomass: conversion into fuels, chemicals, and power, 1st edn. Wiley, Ames, IA, pp 1–11

    Chapter  Google Scholar 

  25. 25.

    Huber GW, Corma A (2007) Synergies between bio- and oil refineries for the production of fuels from biomass. Angew Chem Int Ed 46:7184–7201

    Article  CAS  Google Scholar 

  26. 26.

    Du Y, Chen H, Chen R, Xu N (2006) Poisoning effect of some nitrogen compounds on nano-sized nickel catalysts in p-nitrophenol hydrogenation. Chem Eng J 125:9–14

    Article  CAS  Google Scholar 

  27. 27.

    Hughes R (1984) Deactivation of catalysts. Academic Press, London

    Google Scholar 

  28. 28.

    Maxted EB (1951) The poisoning of metallic catalysts. In: Frankenburg WG, Komarewsky VI, Rideal EK (eds) Advances in catalysis, vol 3. Academic Press Inc, New York, pp 129–178

  29. 29.

    Agblevor FA, Besler S, Wiselogel AE (1995) Fast pyrolysis of stored biomass feedstocks. Energy Fuel 9:635–640

    Article  CAS  Google Scholar 

  30. 30.

    Tillman DA (2000) Biomass cofiring: the technology, the experience, the combustion consequences. Biomass Bioenergy 19:365–384

    Article  Google Scholar 

  31. 31.

    Lemus R, Parrish DJ, Abaye O (2008) Nitrogen-use dynamics in switchgrass grown for biomass. BioEnergy Res 1:153–162

    Article  Google Scholar 

  32. 32.

    Parrish DJ, Fike JH (2005) The biology and agronomy of switchgrass for biofuels. Crit Rev Plant Sci 24:423–459

    Article  Google Scholar 

  33. 33.

    Snyder CS, Leep RH (2007) Fertilization. In: Barnes RF, Nelson CJ, Moore KJ, Collins M (eds) Forages, the science of grassland agriculture. Blackwell Publishing, Ames, IA, pp 355–377

    Google Scholar 

  34. 34.

    Havlin JL, Beaton JD, Tisdale SL, Nelson WL (2005) Nitrogen. In: Soil fertility and fertilizers: an introduction to nutrient management, vol 7. Pearson Education, Inc, New Jersey, pp 97–159

    Google Scholar 

  35. 35.

    Heaton EA, Dohleman FG, Long SP (2009) Seasonal nitrogen dynamics of Miscanthus x giganteus and Panicum virgatum. GCB Bioenergy 1:297–307

    Article  CAS  Google Scholar 

  36. 36.

    Van Heerwaarden LM, Toet S, Aerts R (2003) Current measures of nutrient resorption efficiency lead to a substantial underestimation of real resorption efficiency: facts and solutions. Oikos 101:664–669

    Article  Google Scholar 

  37. 37.

    Heckathorn SA, DeLucia EH (1994) Drought-induced nitrogen retranslocation in perennial C4 grasses of tallgrass prairie. Ecology 75:1877–1886

    Article  Google Scholar 

  38. 38.

    Suzuki J-I, Stuefer J (1999) On the ecological and evolutionary significance of storage in clonal plants. Plant Spec Biol 14:11–17

    Article  Google Scholar 

  39. 39.

    Nagai M, Sato T, Aiba A (1986) Poisoning effect of nitrogen compounds on dibenzothiophene hydrodesulfurization on sulfided NiMo/Al2O3 catalysts and relation to gas-phase basicity. J Catal 97:52–58

    Article  CAS  Google Scholar 

  40. 40.

    Ellens CJ, Brown RC (2012) Optimization of a free-fall reactor for the production of fast pyrolysis bio-oil. Bioresour Technol 103:374–380

    PubMed  Article  CAS  Google Scholar 

  41. 41.

    Heaton EA, Dohleman FG, Long SP (2008) Meeting US biofuel goals with less land: the potential of Miscanthus. GCB Bioenergy 14:2000–2014

    Google Scholar 

  42. 42.

    Lemus R, Brummer EC, Moore KJ, Molstad NE, Burras CL, Barker MF (2002) Biomass yield and quality of 20 switchgrass populations in southern Iowa, USA. Biomass Bioenergy 23:433–442

    Article  CAS  Google Scholar 

  43. 43.

    Vogel KP, Brejda JJ, Walters DT, Buxton DR (2002) Switchgrass biomass production in the Midwest USA: harvest and nitrogen management. Agron J 94:413–420

    Article  Google Scholar 

  44. 44.

    Lewandowski I, Scurlock JMO, Lindvall E, Christou M (2003) The development and current status of perennial rhizomatous grasses as energy crops in the US and Europe. Biomass Bioenergy 25:335–361

    Article  Google Scholar 

  45. 45.

    Fahmi R, Bridgwater AV, Donnison I, Yates N, Jones JM (2008) The effect of lignin and inorganic species in biomass on pyrolysis oil yields, quality and stability. Fuel 87:1230–1240

    Article  CAS  Google Scholar 

  46. 46.

    Beale CV, Long SP (1997) Seasonal dynamics of nutrient accumulation and partitioning in the perennial C4-grasses Miscanthus × giganteus and Spartina cynosuroides. Biomass Bioenergy 12:419–428

    Article  Google Scholar 

  47. 47.

    Waramit N, Moore KJ, Heggenstaller AH (2011) Composition of native warm-season grasses for bioenergy production in response to nitrogen fertilization rate and harvest date. Agron J 103:655–662

    Article  Google Scholar 

  48. 48.

    Lewandowski I, Heinz A (2003) Delayed harvest of miscanthus—influences on biomass quantity and quality and environmental impacts of energy production. Eur J Agron 19:45–63

    Article  Google Scholar 

  49. 49.

    Lewandowski I, Clifton-Brown JC, Andersson B, Basch G, Christian DG, Jorgensen U et al (2003) Environment and harvest time affects the combustion qualities of Miscanthus genotypes. Agron J 95:1274–1280

    Article  Google Scholar 

  50. 50.

    Yorgun S (2003) Fixed-bed pyrolysis of Miscanthus x giganteus: product yields and bio-oil characterization. Energy Sources Part A: Recover Utilization Environ Effects 25:779–790

    CAS  Google Scholar 

  51. 51.

    Schnitzer MI, Monreal CM, Facey GA, Fransham PB (2007) The conversion of chicken manure to biooil by fast pyrolysis I. Analyses of chicken manure, biooils and char by 13C and 1H NMR and FTIR spectrophotometry. J Environ Sci Health Part B Pestic Contam Agric Wastes 42:71–77

    Article  CAS  Google Scholar 

  52. 52.

    Boateng AA, Mullen CA, Goldberg NM, Hicks KB, McMahan CM, Whalen MC et al (2009) Energy-dense liquid fuel intermediates by pyrolysis of guayule (Parthenium argentatum) shrub and bagasse. Fuel 88:2207–2215

    Article  CAS  Google Scholar 

  53. 53.

    Mullen CA, Boateng AA, Goldberg NM, Lima IM, Laird DA, Hicks KB (2010) Bio-oil and bio-char production from corn cobs and stover by fast pyrolysis. Biomass Bioenergy 34:67–74

    Article  CAS  Google Scholar 

  54. 54.

    Ferdi Gercel H (2002) The production and evaluation of bio-oils from the pyrolysis of sunflower-oil cake. Biomass Bioenergy 23:307–314

    Article  Google Scholar 

  55. 55.

    Sensoz S, Demiral I, Ferdi Gercel H (2006) Olive bagasse (Olea europea L.) pyrolysis. Bioresour Technol 97:429–436

    PubMed  Article  Google Scholar 

  56. 56.

    Williams PT, Horne PA (1994) Characterisation of oils from the fluidised bed pyrolysis of biomass with zeolite catalyst upgrading. Biomass Bioenergy 7:223–236

    Article  CAS  Google Scholar 

  57. 57.

    Putun AE (2002) Biomass to bio-oil via fast pyrolysis of cotton straw and stalk. Energy Sources 24:275–285

    Article  CAS  Google Scholar 

Download references


This work was supported by ConocoPhillips Company and the Iowa State University Department of Agronomy. We thank Nicholas Boersma, Nick Ohde, George Patrick, Dave Sundberg, Ryan Smith, Alex Maeder, and Ashley Greve who helped with the project; Preston Gable and Ben Franzen for assisting in the operation of the free-fall reactor; Patrick Johnston for analysis of samples on the TGA; and John Hoyt for analysis of the samples on the CHN analyzer. We thank Nicholas Boersma, Nick Ohde, Scott McQueen, Mark Hughes, and Matt Liebman for the comments on early drafts of this manuscript, and Karl Pazdernik for statistical consulting.

Author information



Corresponding author

Correspondence to Emily A. Heaton.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Wilson, D.M., Dalluge, D.L., Rover, M. et al. Crop Management Impacts Biofuel Quality: Influence of Switchgrass Harvest Time on Yield, Nitrogen and Ash of Fast Pyrolysis Products. Bioenerg. Res. 6, 103–113 (2013).

Download citation


  • Biomass crop
  • Thermochemical conversion
  • Biofuel contaminants
  • Bioenergy
  • Bio-oil
  • Panicum virgatum L.