Novi biorafinerijski pristup za frakcionisanje žetvenih ostataka

Agri-food waste comprises lignocellulosic biomass (LCB), which consists of cellulose, hemicellulose and lignin. This composition makes LCB suitable for producing energy, biofuels, and value-added products within the biorefinery framework. Different pretreatments were developed and widely used to convert lignocellulose into these products. However, many conventional pretreatments are being substituted due to a lack of sustainability, stressing the urge to shift to greener alternatives. This study employed cold plasma as a low-energy technique for corn stalk delignification. Four experimental set-ups were tested for pretreatment – water as a pH-neutral and chemical-free pretreatment, Fenton reagent as acidic, alkaline hydrogen peroxide as an alkaline pretreatment, and natural deep eutectic solvent (NADES) as an emerging green solvent for LCB pretreatment. Each pretreatment was optimised towards achieving the highest delignification rate. Delignified samples were subjected to enzymatic hydrolysis with a commercial mixture of cellulase, hemicellulase and β-glucosidase, Cellic CTec 2 (Novozymes, Denmark) to estimate the biomass digestibility. Selected samples were tested for biomethane production through anaerobic digestion. The highest delignification was achieved with cold plasma/alkaline pretreatment (79%), followed by cold plasma/NADES (75%), cold plasma/Fenton (56%), and finally cold plasma/water pretreatment (52%). Cold plasma/alkaline and cold plasma/NADES pretreatments also showed potential for increasing biomethane yield. After a 30-day-long anaerobic digestion, samples pretreated with cold plasma/alkaline and cold plasma/NADES pretreatment showed an increase in biomethane production compared to the raw biomass by 9% and 18%, respectively. Moreover, the time needed to achieve 80% of the final biomethane yield (t80) was significantly reduced from 13 days for raw biomass to 5 days for cold plasma/alkaline pretreated, and 7 days for cold plasma/NADES pretreated biomass. At the same time, the lignin fraction was successfully recovered for value-added products while preserving the carbohydrate fraction. Cold plasma proved to be a promising pathway for LCB valorisation following circular economy principles.