Process intensification strategies for lignin valorization

Nowadays, the increasing concern about the declining fossil fuel reserves and the environmental impact derived from their use has put considerable interest in lignocellulose exploitation as a renewable source of biofuels and biomaterials, according to the biorefinery concept.Several processes and technologies have been extensively studied in order to optimize biomass treatments aiming to enhance the recovery of its main products: cellulose, hemicelluloses and lignin. Lignin is, in fact, considered a valid substitute to petroleum as a source of aromatics, thanks to its abundance in nature. However, its complex and highly resistant structure limits its further applications, therefore, lignin upgrading is considered extremely challenging: various processes have been developed in recent years, but their feasibility at industrial scale still represents a bottleneck.Recently, process intensification has gained considerable attention in the design of sustainable procedures for lignin valorization. In particular, non-conventional technologies such as Ball milling, Ultrasounds (US) and Microwaves (MW) have recently shown promising results in biomass exploitation, thanks to their ability in generating specific high-energy microenvironments which could enhance process efficiency: mechanochemical and US activation have been mostly applied to biomass pre-treatment, in order to separate its components and enhance lignin extraction yield, while MW have been exploited as a means for lignin depolymerization, achieving higher yields of aromatics in milder reaction conditions. However further efforts should be done to improve profitability through new processes, aiming to reduce the cost associated to bio-derived products.In the present review, recent approaches to lignin valorization are discussed, focusing on new alternative methodologies for process intensification, besides their challenges and feasibility at industrial scale

Microwave-Assisted -Valerolactone Production for Biomass Lignin Extraction: A Cascade Protocol

The general need to slow the depletion of fossil resources and reduce carbon footprints has led to tremendous effort being invested in creating “greener” industrial processes and developing alternative means to produce fuels and synthesize platform chemicals. This work aims to design a microwave-assisted cascade process for a full biomass valorisation cycle. GVL (γ-valerolactone), a renewable green solvent, has been used in aqueous acidic solution to achieve complete biomass lignin extraction. After lignin precipitation, the levulinic acid (LA)-rich organic fraction was hydrogenated, which regenerated the starting solvent for further biomass delignification. This process does not requires a purification step because GVL plays the dual role of solvent and product, while the reagent (LA) is a product of biomass delignification. In summary, this bio-refinery approach to lignin extraction is a cascade protocol in which the solvent loss is integrated into the conversion cycle, leading to simplified methods for biomass valorisation

Emerging Processing Technologies for the Recovery of Valuable Bioactive Compounds from Potato Peels

Potato peel (PP) is the major underutilised by-product in the potato-processing industry and a potential source of valuable bioactive molecules. Among them, glycoalkaloids and polyphenols are important precursors for steroid hormones and natural antioxidants, respectively. Moreover, the huge quantities of industrial potato-peel waste that are produced are a rich source of primary metabolites, which principally include starch as well as non-starch polysaccharides, proteins, lipids, lignin and cellulose. All carbohydrates are prone to undergo fermentation to produce ethanol, lactic and acetic acid. Finally, the main portion of PP is made up of alcohol-insoluble matter with a dietary fibre content of approximatively 40%. The present review summarises the recent advances and emerging technologies in potato-peel extraction and further valorisation processing in the food industry