Investigation of sugar extraction capability from rice paddy straw for potential use of bioethanol production towards energy security

ABSTRACT

Over the past decades, bioethanol has emerged as an important alternative to fossil fuels. Moreover, bioethanol reduces the overall CO₂ emission (greenhouse gas emission) compared to petroleum fuels as these are plant derived. Bioethanol will also provide energy security in the regions/countries where fossil fuels are in scarcity. Bioethanol is produced widely using edible resources like sugarcane, rice, and corn grains, etc. It has been a concern that the edible sources may create problem in food security. With these concerns, non-edible feedstock such as rice paddy straw and corn straw-based lignocellulose biomass has drawn tremendous attention toward the second generation (2G) ethanol production as a sustainable bioenergy source for internal combustion (IC) engine. Cellulose and hemicellulose contents are higher in biomass, which can be used as a source of reducing sugar to produce ethanol. Higher concentration of lignin fibers in the non-edible raw materials makes the sugar extraction challenging. The use of acidic medium such as hydrochloric acid (HCl) and sulfuric acid (H₂SO₄) makes it easier to break down the lignin fibers and enhances the sugar extraction. In this work, varying concentrations of HCl and H₂SO₄ were used to examine and maximize the sugar extraction from rice paddy straw. HCl was observed to provide higher yielding of sugar compared to H₂SO₄. Furthermore, a temperature-variation study (during the hydrolysis process) was also performed to evaluate the variation in sugar yielding with 2.0% HCl (v/v).

GRAPHICAL ABSTRACT

KEYWORDS:

• Lignocellulose
• Acidic pretreatment
• Delignification
• Sugar estimation
• Bioethanol
• Morphological analysis

Acknowledgments

Authors would like to acknowledge the Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Government of India for providing financial support under the start-up grant (SRG) project code: SRG/2019/001664.

Disclosure statement

No potential conflict of interest was reported by the author(s).

List of abbreviations

HCl Hydrochloric acid H₂SO₄Sulfuric acid DNSA3,5-Dinitrosalicylic acid ANSA 3-amino-5-nitrosalicylic acid UV Ultraviolet OD Optical Density NaOH Sodium hydroxide Na₂CO₃ Sodium carbonate FTIR Fourier Transform Infrared Spectroscopy FE-SEM Field emission scanning electron microscope CTAB Cetyl trimethyl ammonium bromide SDS Sodium dodecyl sulfate 2G Second generation

Highlights

• Effect of HCl and H₂SO₄ during delignification was tested for varying acid concentrations for maximum sugar yielding.

• 3,5-dinitrosalicylic acid (DNSA) test was performed for sugar extraction estimation using HCl and H₂SO₄ acidic pre-treated conditions.

• Temperature variation tests were performed to optimize hydrolysis conditions.

• Morphological analysis has been performed for raw and acid-treated rice paddy straw.

• Sugar yielding increases with increase in acid concentration and 2% HCl (v/v) showed the highest sugar yielding.

Additional information

Funding

This work was supported by the Science and Engineering Research Board Department of Science and Technology (DST), Government of India[SRG/2019/001664].