Thermal pretreatment of microalgae for biomethane production: experimental studies, kinetics and energy analysis

Meng Wang, Eunyoung Lee, Merrill P. Dilbeck, Matthew Liebelt, Qiong Zhang, Sarina J. Ergas

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

BACKGROUND: Microalgae grown on wastewater are promising feedstocks for biomethane production by anaerobic digestion. However, the hemicellulose composition of the microalgae cell wall inhibits hydrolysis of intracellular substances and limits their anaerobic digestibility. This study investigated enhancement of biomethane production rates during anaerobic digestion of Chlorella sp. using thermal pretreatment at varying temperatures. Experimental data were fitted to three simplified kinetic models and an energy analysis was performed to gain insights into this potential application of thermal pretreatment. RESULTS: Methane yields from untreated algae were 155 mL g−1 VSadd, while thermal pretreatment at 70 °C and 90 °C for 0.5 h increased the methane yield by 37% and 48%, respectively. Thermal pretreatment at 121 °C for 0.3 h resulted in the highest methane yield (322 mL g−1 VSadd), which is 108% higher than the untreated algae. Data from digestion of thermally pretreated microalgae were best described by a first-order kinetic model. However, for untreated microalgae the Gompertz model, which includes a lag phase, provided the best fit to the methane production data. CONCLUSIONS: Thermal pretreatment improved the maximum methane production rate and shortened the lag period during anaerobic digestion. However, the energy balance indicated that pretreatment of microalgae could not achieve a positive energy balance compared with anaerobic digestion of untreated microalgae. Co-digestion with other biomass or increasing the solids concentration of anaerobic digestion could be used to increase the overall energy efficiency.

Original languageEnglish (US)
Pages (from-to)399-407
Number of pages9
JournalJournal of Chemical Technology and Biotechnology
Volume92
Issue number2
DOIs
StatePublished - Feb 1 2017

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Microalgae
Anaerobic digestion
Methane
Digestion
experimental study
Hot Temperature
methane
kinetics
Kinetics
energy
Algae
Energy balance
energy balance
digestion
alga
digestibility
energy efficiency
Chlorella
Feedstocks
Energy efficiency

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Chemical Engineering(all)
  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Waste Management and Disposal
  • Pollution
  • Organic Chemistry
  • Inorganic Chemistry

Cite this

Wang, Meng ; Lee, Eunyoung ; Dilbeck, Merrill P. ; Liebelt, Matthew ; Zhang, Qiong ; Ergas, Sarina J. / Thermal pretreatment of microalgae for biomethane production : experimental studies, kinetics and energy analysis. In: Journal of Chemical Technology and Biotechnology. 2017 ; Vol. 92, No. 2. pp. 399-407.
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abstract = "BACKGROUND: Microalgae grown on wastewater are promising feedstocks for biomethane production by anaerobic digestion. However, the hemicellulose composition of the microalgae cell wall inhibits hydrolysis of intracellular substances and limits their anaerobic digestibility. This study investigated enhancement of biomethane production rates during anaerobic digestion of Chlorella sp. using thermal pretreatment at varying temperatures. Experimental data were fitted to three simplified kinetic models and an energy analysis was performed to gain insights into this potential application of thermal pretreatment. RESULTS: Methane yields from untreated algae were 155 mL g−1 VSadd, while thermal pretreatment at 70 °C and 90 °C for 0.5 h increased the methane yield by 37{\%} and 48{\%}, respectively. Thermal pretreatment at 121 °C for 0.3 h resulted in the highest methane yield (322 mL g−1 VSadd), which is 108{\%} higher than the untreated algae. Data from digestion of thermally pretreated microalgae were best described by a first-order kinetic model. However, for untreated microalgae the Gompertz model, which includes a lag phase, provided the best fit to the methane production data. CONCLUSIONS: Thermal pretreatment improved the maximum methane production rate and shortened the lag period during anaerobic digestion. However, the energy balance indicated that pretreatment of microalgae could not achieve a positive energy balance compared with anaerobic digestion of untreated microalgae. Co-digestion with other biomass or increasing the solids concentration of anaerobic digestion could be used to increase the overall energy efficiency.",
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Thermal pretreatment of microalgae for biomethane production : experimental studies, kinetics and energy analysis. / Wang, Meng; Lee, Eunyoung; Dilbeck, Merrill P.; Liebelt, Matthew; Zhang, Qiong; Ergas, Sarina J.

In: Journal of Chemical Technology and Biotechnology, Vol. 92, No. 2, 01.02.2017, p. 399-407.

Research output: Contribution to journalArticle

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AU - Wang, Meng

AU - Lee, Eunyoung

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AU - Zhang, Qiong

AU - Ergas, Sarina J.

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N2 - BACKGROUND: Microalgae grown on wastewater are promising feedstocks for biomethane production by anaerobic digestion. However, the hemicellulose composition of the microalgae cell wall inhibits hydrolysis of intracellular substances and limits their anaerobic digestibility. This study investigated enhancement of biomethane production rates during anaerobic digestion of Chlorella sp. using thermal pretreatment at varying temperatures. Experimental data were fitted to three simplified kinetic models and an energy analysis was performed to gain insights into this potential application of thermal pretreatment. RESULTS: Methane yields from untreated algae were 155 mL g−1 VSadd, while thermal pretreatment at 70 °C and 90 °C for 0.5 h increased the methane yield by 37% and 48%, respectively. Thermal pretreatment at 121 °C for 0.3 h resulted in the highest methane yield (322 mL g−1 VSadd), which is 108% higher than the untreated algae. Data from digestion of thermally pretreated microalgae were best described by a first-order kinetic model. However, for untreated microalgae the Gompertz model, which includes a lag phase, provided the best fit to the methane production data. CONCLUSIONS: Thermal pretreatment improved the maximum methane production rate and shortened the lag period during anaerobic digestion. However, the energy balance indicated that pretreatment of microalgae could not achieve a positive energy balance compared with anaerobic digestion of untreated microalgae. Co-digestion with other biomass or increasing the solids concentration of anaerobic digestion could be used to increase the overall energy efficiency.

AB - BACKGROUND: Microalgae grown on wastewater are promising feedstocks for biomethane production by anaerobic digestion. However, the hemicellulose composition of the microalgae cell wall inhibits hydrolysis of intracellular substances and limits their anaerobic digestibility. This study investigated enhancement of biomethane production rates during anaerobic digestion of Chlorella sp. using thermal pretreatment at varying temperatures. Experimental data were fitted to three simplified kinetic models and an energy analysis was performed to gain insights into this potential application of thermal pretreatment. RESULTS: Methane yields from untreated algae were 155 mL g−1 VSadd, while thermal pretreatment at 70 °C and 90 °C for 0.5 h increased the methane yield by 37% and 48%, respectively. Thermal pretreatment at 121 °C for 0.3 h resulted in the highest methane yield (322 mL g−1 VSadd), which is 108% higher than the untreated algae. Data from digestion of thermally pretreated microalgae were best described by a first-order kinetic model. However, for untreated microalgae the Gompertz model, which includes a lag phase, provided the best fit to the methane production data. CONCLUSIONS: Thermal pretreatment improved the maximum methane production rate and shortened the lag period during anaerobic digestion. However, the energy balance indicated that pretreatment of microalgae could not achieve a positive energy balance compared with anaerobic digestion of untreated microalgae. Co-digestion with other biomass or increasing the solids concentration of anaerobic digestion could be used to increase the overall energy efficiency.

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