Solar-energy-driven conversion of biomass to bioethanol: A sustainable approach

Betina Tabah, Indra Neel Pulidindi, Venkateswara Rao Chitturi, Leela Mohana Reddy Arava, Alexander Varvak, Elizabeth Foran, Aharon Gedanken

Research output: Contribution to journalReview articlepeer-review

20 Scopus citations


Bioethanol is one of the most promising transportation fuels with economic, environmental, and energy benefits. However, currently, the production methodologies and purification technologies of the biofuel industry are not economical. This review demonstrates an economically viable, energy efficient, and sustainable alternative to the state-of-the-art process for bioethanol production from biomass. We have developed a solar-thermal-energy-driven simultaneous saccharification and fermentation (SSF) process for single-step conversion of biomass to bioethanol. In the early stages, aqueous solutions of glucose, starch, or cellulose were fed into a specially designed solar reactor containing instant baker's yeast (Saccharomyces cerevisiae) and the necessary enzymes. The yeast (biocatalyst) was not supplemented by any other nutrient, and it was demonstrated that the same yeast and enzymes could be used for at least two months without any decrease in enzymatic activity. After obtaining very high yields (up to 91% of the theoretical yield) and excellent separation of ethanol from the fermentation broth, the methodology was successfully extended to a continuous-flow single-step conversion of marine algae Ulva rigida to bioethanol (84% of the theoretical yield). Harnessing solar thermal energy for driving the SSF reaction as well as the special design of the solar reactor that facilitates in situ separation of ethanol from the fermentation broth by an evaporation-condensation process make the current method industrially appealing and adoptable for large-scale production. This review explores new avenues for a decentralized power supply based on solar thermal energy. The bioethanol produced in this study was demonstrated as a potential fuel for direct ethanol fuel cells with high current and power density values, and 65% thermodynamic efficiency. In addition, the secondary metabolite glycerol was fully reduced to the value-added product 1,3-propanediol by S. cerevisiae, which is the first example of a fungal strain converting glycerol in situ to 1,3-propanediol. In this review, we aim to discuss the current methodologies and recent developments for bioethanol production from biomass and demonstrate the future aspects of bioethanol production in solar reactors, and strategies to improve process yields as well as the prospects of using a solar reactor to produce other valuable chemicals.

Original languageEnglish
Pages (from-to)15486-15506
Number of pages21
JournalJournal of Materials Chemistry A
Issue number30
StatePublished - 2017

Bibliographical note

Funding Information:
The authors acknowledge the financial support from the Israel Science Foundation (ISF, Grant No. 598/12), from the Ministry of Science, Technology, and Space of Israel (Grant No. 3-9802 and 3-99763), and from the Israel Ministry of National Infrastructures, Energy and Water Resources (Grant No. 3-13442). The authors thank Mr Menachem Schneeberg, head of mechanical workshop at Bar-Ilan University, for fabricating the solar reactor. The authors are also grateful to Dr Hugo Gottlieb, head of the NMR unit at Bar-Ilan University, for fruitful discussions on NMR analysis.

Publisher Copyright:
© 2017 The Royal Society of Chemistry.


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