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Title: Synergistic co-digestion of wastewater grown algae-bacteria polyculture biomass and cellulose to optimize carbon-to-nitrogen ratio and application of kinetic models to predict anaerobic digestion energy balance

Abstract

Anaerobic digestion of feedstocks with imbalanced C/N ratios leads to reduced conversion rates and methane yield. The current study investigated enhancing methane production and, therefore, energy output and efficiency, from digesting wastewater grown algal-bacteria polyculture biomass by adjusting the C/N ratio through co-digestion with a nitrogen-poor material – cellulose. Four kinetic models, including 1st-order, pseudo-parallel 1st-order, modified Gompertz, and transference function equations, were evaluated for their ability to describe the biogas and methane production from mono-digestion and co-digestion of algal and cellulose biomass. Our data show that increasing the algal biomass C/N ratio from its original value of 5.7 to optimal values of 20-30 by co-digesting with cellulosic biomass (optimal algae to cellulose ratios of 35%:65% and 20%:80%) improves the ultimate methane production by more than 10% compared to mono-digestion. Importantly, the synergistic effects from co-digestion were most significant during the initial phase of fermentation with the cumulative methane yield for the first ten days increasing up to 100%. Further, the modified Gompertz kinetic model most accurately predicted that co-digestion improves the process by shortening the time-lag for methane generation by nearly 50% and by increasing the methane production rate by nearly 35%. The synergy from co-digestion led to boostingmore » the total energy output (combined heat and electricity) and net energy ratio by 30-40% and 20%, respectively. Implementation of a co-digestion approach allows for downsizing volumes for new anaerobic digesters or enhancing methane production in existing digesters.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1503493
Report Number(s):
PNNL-SA-134422
Journal ID: ISSN 0960-8524
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Bioresource Technology
Additional Journal Information:
Journal Volume: 269; Journal Issue: C; Journal ID: ISSN 0960-8524
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
anaerobic co-digestion of algae with cellulose, synergistic effects on methane yield, carbon to nitrogen ratio, biogas and methane production kinetic models, digester energy balance, net energy ratio

Citation Formats

Bohutskyi, Pavlo, Phan, Duc, Kopachevsky, Anatoliy M., Chow, Steven, Bouwer, Edward J., and Betenbaugh, Michael J. Synergistic co-digestion of wastewater grown algae-bacteria polyculture biomass and cellulose to optimize carbon-to-nitrogen ratio and application of kinetic models to predict anaerobic digestion energy balance. United States: N. p., 2018. Web. doi:10.1016/j.biortech.2018.08.085.
Bohutskyi, Pavlo, Phan, Duc, Kopachevsky, Anatoliy M., Chow, Steven, Bouwer, Edward J., & Betenbaugh, Michael J. Synergistic co-digestion of wastewater grown algae-bacteria polyculture biomass and cellulose to optimize carbon-to-nitrogen ratio and application of kinetic models to predict anaerobic digestion energy balance. United States. doi:10.1016/j.biortech.2018.08.085.
Bohutskyi, Pavlo, Phan, Duc, Kopachevsky, Anatoliy M., Chow, Steven, Bouwer, Edward J., and Betenbaugh, Michael J. Sat . "Synergistic co-digestion of wastewater grown algae-bacteria polyculture biomass and cellulose to optimize carbon-to-nitrogen ratio and application of kinetic models to predict anaerobic digestion energy balance". United States. doi:10.1016/j.biortech.2018.08.085.
@article{osti_1503493,
title = {Synergistic co-digestion of wastewater grown algae-bacteria polyculture biomass and cellulose to optimize carbon-to-nitrogen ratio and application of kinetic models to predict anaerobic digestion energy balance},
author = {Bohutskyi, Pavlo and Phan, Duc and Kopachevsky, Anatoliy M. and Chow, Steven and Bouwer, Edward J. and Betenbaugh, Michael J.},
abstractNote = {Anaerobic digestion of feedstocks with imbalanced C/N ratios leads to reduced conversion rates and methane yield. The current study investigated enhancing methane production and, therefore, energy output and efficiency, from digesting wastewater grown algal-bacteria polyculture biomass by adjusting the C/N ratio through co-digestion with a nitrogen-poor material – cellulose. Four kinetic models, including 1st-order, pseudo-parallel 1st-order, modified Gompertz, and transference function equations, were evaluated for their ability to describe the biogas and methane production from mono-digestion and co-digestion of algal and cellulose biomass. Our data show that increasing the algal biomass C/N ratio from its original value of 5.7 to optimal values of 20-30 by co-digesting with cellulosic biomass (optimal algae to cellulose ratios of 35%:65% and 20%:80%) improves the ultimate methane production by more than 10% compared to mono-digestion. Importantly, the synergistic effects from co-digestion were most significant during the initial phase of fermentation with the cumulative methane yield for the first ten days increasing up to 100%. Further, the modified Gompertz kinetic model most accurately predicted that co-digestion improves the process by shortening the time-lag for methane generation by nearly 50% and by increasing the methane production rate by nearly 35%. The synergy from co-digestion led to boosting the total energy output (combined heat and electricity) and net energy ratio by 30-40% and 20%, respectively. Implementation of a co-digestion approach allows for downsizing volumes for new anaerobic digesters or enhancing methane production in existing digesters.},
doi = {10.1016/j.biortech.2018.08.085},
journal = {Bioresource Technology},
issn = {0960-8524},
number = C,
volume = 269,
place = {United States},
year = {2018},
month = {12}
}