The PRIN (Research Project with Relevant National Interest) project “Biocheaper—biomasses circular holistic economy approach to energy equipments” started in September 2019 and involves several universities: Palermo as the university coordinator, Perugia, Cassino, Enna, Pavia and Bolzano. The main goal of the project is to increase the energy efficiency and reduce the pollutants emissions in small-scale biomass plant for energy (heat and power) production. The project focuses on residual lignocellulosic feedstocks from the agriculture and forestry sector, from energy crops in marginal lands and residues from rivers maintenance. Starting from the selection and characterization of potential feedstocks, the project aims at developing some prototypes for retrofit applications in existing biomass boilers, like a mini-cyclone for the reduction of particulate emissions and an exhaust air-water condensing system for the recovery of water and the reuse in agriculture. This work presents the first results of the project, in particular regarding the selection and the chemical–physical characterization of different biomass, available in different zones of Italy; in particular the authors investigated cardoon chips, carthamus chips, olive and wine pruning, residues from rivers maintenance. Each biomass sample was characterized in terms of moisture content, ashes content, volatile substances, fixed carbon, low and high heating value, content of carbon, nitrogen, hydrogen and main metals.

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One of the primary targets for the new lignocellulosic feedstock-based biorefinery is the simultaneous valorization of holocellulose and lignin. Acidified organosolv treatment is among the most promising strategy for recovering technical lignin, water-soluble hemicellulose, and cellulose pulp with increased accessibility to hydrolytic enzymes. In this work, a design-of-experiment (DoE) approach was used to increase the cellulose recovery, digestibility, and the delignification of Cynara cardunculus L. feedstock. In the first treatment, the milled biomass was subjected to microwave-assisted extraction using an acidified GVL/water mixture to separate lignin and hemicellulose from cellulose. In the second treatment, the cellulose pulp was hydrolyzed by cellulolytic enzymes to demonstrate the enhanced digestibility. At the optimal condition (154 °C, 2.24% H2SO4, and 0.62 GVL/water ratio), the cellulose pulp showed a cellulose content of 87.59%, while the lignin content was lower than 8%. The cellulose recovery and digestibility were equal to 79.46% and 86.94%, respectively. About 40% of the initial hemicellulose was recovered as monosaccharides. This study demonstrated the effectiveness of the two-step organosolv treatment for biomass fractionation; however, as suggested by DoE analysis, a confirmative study at a low temperature (<154 °C) should be performed to further increase the cellulose recovery.

Cardoon (Cynara cardunculus) is a promising crop from which to obtain oilseeds and lignocellulosic biomass. Acid-catalyzed steam explosion is a thermochemical process that can efficiently pre-treat lignocellulosic biomass. The drawback is the production of a high number of carbohydrate degradation products in the liquid fraction that could inhibit microbial growth. In this work, the lignocellulosic biomass of cardoon, gathered from a dedicated field, were used as the raw material for the production of fermentable monosaccharides by employing acid-catalyzed steam explosion. The raw material was pre-soaked with a dilute 1% (w/w) sulfuric acid solution and then subjected to steam explosion under three different severity conditions. The recovered slurry was separated into solid and liquid fractions, which were individually characterized to determine total carbohydrate and inhibitor concentrations. The slurry and the washed solid fraction underwent enzymatic hydrolysis to release glucose and pentose monosaccharides. By conducting the pre-treatment at 175 °C for 35 min and hydrolyzing the obtained slurry, a yield of 33.17 g of monosaccharides/100 g of cardoon was achieved. At the same conditions, 4.39 g of inhibitors/100 g of cardoon were produced.

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