Non-conventional strategies for pretreatment of lignocellulosic biomass for production of value-added products: a sustainable and circular economy approach

The growing global population is driving up energy demand. The continued reliance on conventional energy sources is contributing to global warming and significant emissions of harmful gases. Conventional energy sources, such as coal, crude oil, and natural gas, commonly used in petrochemical processes, must be replaced with sustainable alternatives. One of the most popular and affordable sources for producing renewable energy and chemicals is lignocellulosic biomass (LCB). Lignocellulosic biomass, which includes agricultural waste, energy crops, and forest residues, is readily available, cost-effective, and provides a sustainable feedstock for bio-based energy and chemical production. To break down the natural structure of lignocellulosic biomass and facilitate the separation of its components for various applications, pretreatment is essential. Conventional pretreatment methods, however, have significant drawbacks; they tend to be toxic, environmentally polluting, and expensive compared to non-conventional approaches. To address these issues, we must shift toward less harmful, eco-friendly strategies. Techniques such as microwave, ultrasound, irradiation, hydrodynamics, and pulsed electric fields are promising alternatives, generating fewer toxic by-products and being more environmentally friendly. This paper explores the benefits, limitations, and mechanisms of specific non-conventional pretreatment methods, as well as the role of lignocellulosic biomass in biomass valorization and the circular economy.