Complete valorisation of giant reed: integrated exploitation of hemicellulose, cellulose and lignin fractions towards valuable bio-based products adopting green process conditions

The economic sustainability of modern industrial-scale biorefinery models is strongly affected by the cost and the availability of raw materials. In this perspective, the exploitation of low or negative value biomasses, such as agro-industrial wastes and non-food crops, and the complete valorisation of all the fractions of the starting material represent crucial strategies to favour the development of 2nd- and 3rd-generation biorefineries. Biorefining of lignocellulosic biomass, containing hemicellulose, cellulose and lignin, generates hexose/pentose sugars and aromatic compounds which are versatile platform chemicals as they can be converted into fuels, solvents, materials and fine chemicals. Moreover, lignin-rich residues can be converted into activated carbon which presents many applications as an adsorbent biomaterial. The present study developed an innovative and integrated biorefinery process based on the complete and sustainable valorisation of cellulose, hemicellulose and lignin fractions of the non-food crop giant reed (Arundo donax L.). Giant reed is a promising low-cost and perennial biomass able to grow on marginal, contaminated or underutilised lands and it is characterised by high production yield (35-40 ton/h/y), high carbohydrates content (55-65 wt%) and low input management systems [1]. Different chemo- and bio-catalytic approaches were optimised in order to develop a cascade conversion of hemicellulose, cellulose and lignin to various marketable bioproducts [1], according to Figure 1. Figure 1 – Integrated biorefinery scheme for the full exploitation of giant reed. In the first step, microwave-assisted FeCl3- or Amberlyst-70-catalysed hemicellulose conversion to xylose or furfural was performed and optimised. In the second step, microwave-assisted FeCl3- or recycled Amberlyst-70-catalysed cellulose conversion to glucose or levulinic and formic acids was tested and optimised. As an alternative, the enzymatic hydrolysis of cellulose to glucose was studied. The final lignin-rich solid residue was used to produce activated carbon for the CO2 adsorption. In the last step, xylose- and glucose-rich hydrolysates were converted by fermentation to single cell oil which was used to produce new generation biodiesel.