Bioethanol production from acid pretreated microalgal hydrolysate using microwave-assisted heating wet torrefaction

Kai Ling Yu, Wei-Hsin Chen, Herng-Kuang Sheen, Jo-Shu Chang, Chih-Sheng Lin, Hwai Chyuan Ong, Pau Loke Show, Tau Chuan Ling

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Abstract

This study focused on the bioethanol production from the co-production of solid biochar and liquid hydrolysate under microwave-assisted heating wet torrefaction towards a sustainable green technology. The two indigenous microalgal biomass undergone dilute acid pretreatment using wet torrefaction to produce microalgal hydrolysates and biochar at operating conditions of 160-170 degrees C with holding times of 5-10 min. The hydrolysates were utilized for fermentation with the yeast Saccharomyces cerevisiae at 29 degrees C in a dark condition at a non-agitation state for 120 h. The concentrations of total reducing sugar, reducing sugar by-product, and bioethanol in the hydrolysates were determined. The carbohydrate-rich microalga C. vulgaris ESP-31 showed a good performance in bioethanol production. Microalgal hydrolysate obtained after the pretreatment consisted of a total reducing sugar with the highest concentration of 98.11 g/L. The formation of by-product 5-hydroxymethyl-2-furaldehyde (5 HMF), which might act as the fermentation inhibitor that led to the low ethanol yield, was also analyzed. The highest ethanol yield achieved was 7.61% with a maximum experimental conversion probability of 95.22%. This study has demonstrated the feasible bioethanol production from microalgal hydrolysate through microwave-assisted heating wet torrefaction using dilute acids and the optimization of bioethanol production can be carried out for better performance in the future study.

Original languageEnglish
Article number118435
Number of pages11
JournalFuel
Volume279
DOIs
StatePublished - 1 Nov 2020

Keywords

  • Bioethanol and biochar
  • Wet torrefaction
  • Microalgae
  • Hydrolysate
  • Acid hydrolysis
  • Alternative fuel
  • OF-THE-ART
  • SULFURIC-ACID
  • HYDROTHERMAL CARBONIZATION
  • BIOMASS TORREFACTION
  • BIOCHAR PRODUCTION
  • SEWAGE-SLUDGE
  • CO-PYROLYSIS
  • WASTE-WATER
  • FERMENTATION
  • ETHANOL

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