The origin, composition, and applications of industrial humins – a review

Abstract

Humins are side-products derived from the acid-catalysed conversion of carbohydrate-containing biomass, including sugars (e.g. glucose, fructose, sucrose), oligosaccharides, polysaccharides, and lignocellulosic feedstocks into hydroxymethylfurfural (HMF), furfural, and levulinic acid. Until recently, humins were primarily burned as a power and heat source, but now several higher value applications for humins are within reach. This review covers the history, state of the art, and future outlook on the subject of industrial humins, including humins origin, production conditions, compositions, characterisation, and proposed structures. Current opinion on humins formation mechanisms, including kinetic studies, ways to minimise their production, established valorisation routes, and novel applications are also discussed.