Abstract
BackgroundToday, most of pretreatments used to convert biomass into biofuels are based on expensive chemical processes that not only do not keep the major components intact after separation, but also consume water and generate many effluents. However, dry fractionation technologies are an important step for future biomass biorefineries since they do not require chemicals and do not generate wastewater. Therefore, the aim of the present study was to evaluate the feasibility of using milling combined with an electrostatic fractionation (ES) of wheat straw (WS) as a way to separate fractions that are enriched in cellulose and more enzymatically accessible, from recalcitrant tissues enriched in lignin-hemicelluloses, in order to produce biofuels.ResultsAfter milling, WS particles are introduced into a tribo-electrostatic separator, where they are positively or negatively charged by tribo-electricity. Then they are introduced into a separation cell comprising two electrodes (+ and –). The negative electrode attracts the positively charged particles and the positive electrode attracts the negatively charged particles. Results show that amorphous cellulose rich particles were clearly more abundant in positively charged fractions (F+), and loose crystalline cellulose, lignin-xylan and ash-containing material were more abundant in negatively charged fractions (F–). Indeed, positively charged fractions (F+) are more accessible upon enzymatic hydrolysis, which resulted, for example, in sugars yield of 43.5% glucose (254 gKg−1) for F2B + compared to 25.2% (103 gKg-1) for F2A–, and 26.3% (130 gKg−1) for unfractionated WS F0, respectively.ConclusionsThe combination strategy of milling and ES fractionation could improve the economic feasibility by low energy consumption (10.5 WhKg−1) and it produces reactive lignocelluloses particles with different physicochemical structures, which can be converted easily into biofuels and biomaterials without generating toxic effluents.
Highlights
Today, most of pretreatments used to convert biomass into biofuels are based on expensive chemical processes that do not keep the major components intact after separation, and consume water and generate many effluents
The aim of the present study was to evaluate the potential of using ultrafine grinding followed by electrostatic fractionation as a way to obtain or separate different tissues enriched in cellulose and/or lignin-hemicelluloses from wheat straw (WS) for biofuels and biomaterials production
Structural properties and biochemical composition of wheat straw fractions prepared by electrostatic separation technology On an industrial scale, electrostatic separation (ES) is used as a technology for electric or polymers waste separation
Summary
Most of pretreatments used to convert biomass into biofuels are based on expensive chemical processes that do not keep the major components intact after separation, and consume water and generate many effluents. A dry fractionation or refinery of lignocellulosic biomass without using chemical and water could allow to produce different tissues enriched in cellulose, hemicelluloses and/or lignin and increase the efficiency of processes while reducing the associated costs and effluent production [7,10]. These processes are based on a combination of fragmentation and separation steps, which are carried out by a mechanical pretreatment followed by several types of fractionation technologies [11,12,13]
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