A molar basis comparison of calcium hydroxide, sodium hydroxide, and potassium hydroxide on the pretreatment of switchgrass and miscanthus under high solids conditions

Carla Inês Soares Rodrigues, Joshua J. Jackson, Michael D. Montross

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

Pretreatment is an essential step in the formation of liquid biofuels. Switchgrass and miscanthus were pretreated using calcium hydroxide, potassium hydroxide, and sodium hydroxide at an equivalent hydroxyl concentration (0.46 g OH/g dry biomass), at a solids content of 40%, and two temperatures (25 and 50 °C) for seven days. The cellulose, hemicellulose, and lignin composition before and after pretreatment were quantified according to the standard procedures developed by the National Renewable Energy Laboratory. After pretreatment, enzyme hydrolysis was performed at 50 °C in a shaking incubator with an enzyme loading of 60 FPU/g cellulose. Potassium and sodium hydroxide led to the largest reduction in lignin of between 30–47% with the two feedstocks and two temperature levels. Calcium hydroxide had a significantly lower amount of delignification of between 13–21%. Sodium and potassium hydroxide had a similar maximum reaction rate, except for switchgrass pretreated at 50 °C where the reaction rate was lower for potassium hydroxide. Cellulose conversion was the highest for sodium and potassium hydroxide and varied between 56.1 and 80.5% for both feedstocks at the two pretreatment temperatures investigated. Calcium hydroxide demonstrated a significantly lower cellulose conversion that varied between 23.0 and 44.9%. The results indicated that with an equivalent molar basis of OH, potassium and sodium hydroxide had superior performance relative to calcium hydroxide in a high solids environment.

Original languageEnglish
Pages (from-to)165-173
Number of pages9
JournalIndustrial Crops and Products
Volume92
DOIs
StatePublished - Dec 15 2016

Bibliographical note

Funding Information:
The authors sincerely acknowledge the financial support of the United States Department of Agriculture National Institute for Food and Agriculture Biomass Research and Development Initiative Grant # 2011-10006-30363 . This is publication No. 16-15-085 of the Kentucky Agricultural Experiment Station and is published with the approval of the Director. This work is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, Hatch- Multistate under 1002344 and 1003563 .

Publisher Copyright:
© 2016

Keywords

  • Alkaline pretreatment
  • Dedicated energy crops
  • Enzymatic hydrolysis
  • High solids
  • Molar basis

ASJC Scopus subject areas

  • Agronomy and Crop Science

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