Extraction Behaviors of Lignin and Hemicellulose-Derived Sugars During Organosolv Fractionation of Agricultural Residues Using a Bench-Scale Ball Milling Reactor

Tae Hoon Kim,Tae Hyun Kim,Kyeong Keun Oh,Hyun Kwak

doi:10.3390/en13020352

Abstract

Ethanol organosolv fractionation combined with ball milling was conducted on three major agricultural residues: Rice husk (RH), rice straw (RS), and barley straw (BS). The highest lignin extraction yields of RH, RS, and BS were 55.2%, 53.1%, and 59.4% and the purity of lignin recovered was 99.5% for RH and RS, and 96.8% for BS, with similar chemical characteristics, i.e., low molecular weight distributions (1453–1817 g/mol) and poly dispersity index (1.15–1.28). However, considering the simultaneous production of hemicellulose-derived sugars, distinctive fractionation behaviors were shown for the three agricultural residues. The highest hemicellulose-derived sugar yield was 73.8% when RH was fractionated at 170 °C for 30 min. Meanwhile, very low sugar yields of 31.9% and 35.7% were obtained from RS and BS, respectively. The highest glucan-to-glucose conversion yield from enzymatic hydrolysis of fractionated RH reached 85.2%. Meanwhile, the enzymatic digestibility of the fractionated RS and BS was 60.0% and 70.5%, respectively. Consequently, the fractionation efficiency for RH can be improved with fine refinement. For the case of RS, other fractionation process should be applied to achieve effective fractionation performance.

Highlights

Due to the enormous challenges posed by increasingly severe climate change, lignocellulosic biomass, a renewable and sustainable resource, has been considered as a promising alternative to the finite oil reserves as it can be used to produce alternative fuels and chemicals [1]
These results suggest that the factor that greatly affects the enzyme hydrolysis reaction was the removal was the removal of components other than cellulose from the lignocellulosic biomass
To address the importance of lignin valorization in the biorefinery industry, an organosolv fractionation involving ball milling was conducted at a bench scale on three agricultural residues

Summary

Introduction

Due to the enormous challenges posed by increasingly severe climate change, lignocellulosic biomass, a renewable and sustainable resource, has been considered as a promising alternative to the finite oil reserves as it can be used to produce alternative fuels and chemicals [1]. Numerous efforts have been made to study how to effectively utilize various lignocellulosic biomass, including those obtained from agricultural residues, forest residues, and energy crops [4]. It is assumed that one of the aforementioned various agricultural resources must offer an important renewable source that is a byproduct of crop cultivation and has a structure that is more accessible by enzymes or other chemicals compared to other biomass and is expected to play an Energies 2020, 13, 352; doi:10.3390/en13020352 www.mdpi.com/journal/energies. Some of the agricultural byproducts produced are used in animal feeding, animal bedding, soil mulching, composting, and household fuels, but most of it is generally incinerated and disposed on-farm, which has a negative impact on human health and the environment [5]

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