Cold alkaline extraction of Elephant grass for optimal subsequent extraction of hemicelluloses and energy production

Abstract

There is growing scientific and industrial interest in obtaining useful substances by fractionating lignocellulosic biomass from non-food plant crops for use by the bioenergy industry. The primary goals are to ensure process sustainability and to comply with the principles of circular economy. In this work, we optimized energy production from Elephant grass by previously using cold alkaline extraction to remove its hemicellulose fraction. Elephant grass contains a high proportion of lignin (20%) and hemicelluloses (27.4%), and therefore is an excellent alternative to wood materials for energy production by direct burning. Energy production was optimized to identify the best operating conditions among those tested, namely: alkali concentrations of 80–120 g NaOH L–1, temperatures of 20–40 °C, and treatment times of 30–90 min. Using the optimum conditions thus established (viz., 100 g NaOH L–1, 30 °C, and 30 min) raised the high heating value (HHV) to 19.151 MJ kg–1 (i.e., by 4% relative to the starting material). Also, it allowed the content in elemental C to be preserved, that in H increased by 4.86% and, more environmentally significant, most sulphur (46.9%) to be removed from the solid phase upon treatment. Cold alkaline extraction of the raw material additionally enabled relatively selective separation of the hemicellulose fraction from the cellulose and lignin fractions. Thus, 30.1% of all hemicellulose was dissolved in the treatment liquor and made valorizable while 93.0% of cellulose and 82.1% of lignin present in the raw material remained in the solid phase.

Comparative Analysis of Acidic and Alkaline Pretreatment Techniques for Bioethanol Production from Perennial Grasses

“…Perennial grasses, also known as native or herbaceous crops, stand out for their straightforward cultivation compared to annual crops; they offer advantages in terms of cost-effective cultivation, minimal water, fertilizer, and pesticide requirements, and adaptability to various climates, including marginal lands with poor soil quality, thus making them highly cost-effective [18][19][20][21][22]. Perennial grasses offer the potential to mitigate concerns related to land use, competition between food and fuel production, and other environmental threats compared to annual crops [23].…”

“…Perennial grasses offer the potential to mitigate concerns related to land use, competition between food and fuel production, and other environmental threats compared to annual crops [23]. Moreover, at the end of their growth cycle, they exhibit impressively low moisture content and feature high cellulose content compared with other plant varieties [18]. Therefore, they hold significant promise as bioenergy crops because of their substantial carbohydrate content.…”

Efficient fractionation of pure hemicellulose with high DP from bleached hardwood pulp using LiBr·3H2O and co-production of dissolving pulp

“…20 Cold caustic extraction (30 °C) was used to isolate the hemicellulose fraction from elephant grass, but only 30.1% of the hemicellulose was dissolved in the alkali solution. 21 Actually, cold caustic extraction is a traditional method for upgrading paper-grade pulp to dissolving pulp via removal of hemicellulose. 22 However, the degradation of polysaccharides (e.g., end-wise peeling reaction and reduction of DP) is unavoidable to different extents, depending on the conditions of alkali extraction.…”