Multiproduct biorefinery based on almond shells: Impact of the delignification stage on the manufacture of valuable products

• Published in: Bioresource technology Vol. 315; p. 123896
• Main Authors: Morales, Amaia, Hernández-Ramos, Fabio, Sillero, Leyre, Fernández-Marín, Rut, Dávila, Izaskun, Gullón, Patricia, Erdocia, Xabier, Labidi, Jalel
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-11-2020
• Subjects: Almond shells; Biorefinery; Cellulose; Hemicellulosic oligosaccharides; Lignin; Lignin; Almond shells; Biorefinery; Hemicellulosic oligosaccharides; Cellulose
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2020.123896

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•An integral valorisation of almond shells was successfully performed.•Autohydrolysis treatment allowed high hemicelluloses removal.•High purity lignins were obtained by organosolv and alkaline treatments.•Bleached solids yielded higher glucan conversions in enzymatic hydrolysis.•Cellulose nanocrystals were effectively produced from bleached pulps.
In this work, an integral valorisation of almond shells through a biorefinery approach was studied. The three main components of almond shells were extracted, isolated and characterised. The autohydrolysis process permitted the extraction of the hemicellulosic fraction obtaining a liquor rich in xylooligosaccharides (22.12 g/L). Then, two different delignification processes, alkaline and organosolv treatments, were proposed to obtain a very high purity lignin (≈90%) which could be further valorised for a wide variety of applications. The valorisation of the high cellulosic content of the delignified solids was carried out using two different methods. On the one hand, producing cellulose nanocrystals and on the other hand obtaining glucose by an enzymatic hydrolysis as well as a spent solid mainly composed by lignin (≈78 wt%). Thus, the proposed biorefinery approach could contribute to a circular economy as all the main components of the almond shells could be revalorised by environmentally friendly procedures.