Enhancing lignocellulosic biomass pretreatment with choline chloride-based deep eutectic solvents
Farida Baraka, Mahsa Mousavi Langari, Itsasne Beitia, Izaskun Dávila, Jalel Labidi, Amaia Morales, Leyre Sillero
Abstract
Excessive reliance on fossil fuels has triggered environmental challenges such as greenhouse gas emissions and climate change, prompting a shift towards renewable energy and chemicals. In response, scientists have pioneered sustainable processes like biorefineries to convert biomass into energy, fuels, chemicals, and materials. Lignocellulosic biomass, composed primarily of cellulose, hemicelluloses and lignin, presents a challenge due to its intricate interconnections that hinder effective conversion. Therefore, effective pretreatment strategies are crucial to fractionate these components for downstream processing. Chemical and physicochemical methods show strong potential, despite their energy demands and environmental impact. Recent advancements aligned with Green Chemistry principles, have introduced more sustainable alternatives, including the use of ionic liquids and Deep Eutectic Solvents (DESs). DESs are especially attractive due to their affordability, environmental benignity, biodegradability, and straightforward preparation process. This review highlights the main types of choline chloride based DESs—acidic, basic, and neutral—employed in the treatment of lignocellulosic biomass. Despite DESs’ benefits like low temperatures and shorter reaction times, energy consumption remains high under severe conditions. To mitigate this, recent studies have explored intensification techniques, including microwaves and ultrasounds, to enhance efficiency and sustainability. Combining DESs with other solvents (e.g., water or biphasic systems) is also being explored to modify their properties and enhance product recovery, though these methods are still in early development. Future research should aim to optimize DESs formulations, better understand their interactions with various biomass types, and refine delignification mechanism to improve efficiency under milder conditions. • DESs interacts easily with lignin and hemicelluloses, making biorefineries viable. • Choline chloride based DESs are promising for lignocellulosic biomass pretreatment. • Combining DESs with other intensification techniques have shown promising results.