Effect of Ammonia Soaking Pretreatment and Enzyme Addition on Biochemical Methane Potential of Switchgrass

  • Himmelsbach J
  • Raman D
  • Anex R
 et al. 
  • 22


    Mendeley users who have this article in their library.
  • 19


    Citations of this article.


This article presents the biochemical methane potential (BMP) results from the anaerobic digestion (AD) of switchgrass. Triplicate BMP assays were performed on: untreated switchgrass, aqueous ammonia soaking (AAS) pretreated switchgrass (soaked in 29.5% reagent‐grade aqueous ammonia at 5 L kg‐1 switchgrass for 5 d), and AAS‐pretreated switchgrass plus cellulytic enzymes at 12.5, 25, 62.5, and 125 filter paper units (FPU) enzyme g‐1 volatile solids (VS). Biogas production and biogas methane content were measured daily in all treatments for 21 d. Both biogas and corrected methane production varied significantly among treatments, especially during the first 7 d of the BMP period. Total methane production at 21 d was corrected for enzyme degradation, and methane yields ranged from 0.15 to 0.36 m3 CH4 kg‐1 VS. We compared the corrected energy yield of biogas from switchgrass to prior reports of the energy yield of ethanol from switchgrass via simultaneous saccharification and fermentation (SSF). The AD of AAS‐pretreated switchgrass at the highest enzyme loading rates resulted in a 120% increase in energy extracted as compared to AAS‐pretreated switchgrass converted to ethanol via SSF. Overall, the addition of enzymes to AAS‐pretreated switchgrass greatly accelerated the rate of methane production over the untreated switchgrass and AAS‐pretreated switchgrass without enzymes. However, the process economics are not clear, and additional work is needed to determine whether pretreating switchgrass with aqueous ammonia and/or enzymes before AD is economically advantageous.

Author-supplied keywords

  • Anaerobic digestion
  • Aqueous ammonia soaking
  • BMP.
  • Biochemical methane potential
  • Biogas
  • Biomass pretreatment

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Get full text


  • J. N. Himmelsbach

  • D. R. Raman

  • R. P. Anex

  • R. T. Burns

  • C. R. Faulhaber

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free