Nowadays, the transformation of lignocellulosic biomass into added-value products, such as bio-based platform chemicals, biofuels and biofuel additives, is attracting great attention. In this research, the acid-catalyzed hydrolysis of waste residues of grape pomace and Cynara Cardunculus L. (cardoon), remained after wine and oil exploitation respectively, to levulinic acid was investigated. The grape pomace residue was employed as received, whereas the cardoon one was used both as received and after a steam explosion treatment, being the obtained feedstock enriched in cellulose. Since both these types of waste biomasses are low value materials, this investigation was performed adopting the High Gravity approach, using biomass loadings as higher as possible to achieve the maximum levulinic acid concentration in the hydrolyzates, at the same time maintaining an appreciable yield. Moreover, the effect of the main reaction parameters was assessed. Under the optimized reaction conditions, starting from grape pomace residue, the levulinic acid yield and concentration of 49.5 mol% and 8.5 g/L were reached respectively, whereas, from cardoon residue, levulinic acid yields and concentrations up to 53 mol% and 62 g/L were attained, highlighting the cardoon biomass as the most promising feedstock. On this basis, preliminary studies on the one-pot alcoholysis of cardoon in n-butanol to n-butyl levulinate were performed and the achieved results demonstrate the possibility of its direct production. In summary, this work proves that the cardoon waste biomass is a promising feedstock for the sustainable production of both levulinic acid and alkyl levulinates, paving the way towards a real circular economy.