Enhanced hydrolysis of lignocellulosic waste using highly efficient ozone pretreatment in a venturi system: a comparison of free and strainer models

This study investigates ozone pretreatment processes for lignocellulosic waste, a potentially more sustainable alternative for bioethanol, biogas, and bioplastics production. Traditional methods are often energy-intensive and generate pollutants, limiting large-scale applications. We tested two pretreatment methods using cardboard as a model. The ozone was applied using a venturi system in two settings: the ‘Strainer model’, where ground cardboard is enclosed in a mesh strainer, and the ‘Free model’, where the cardboard circulates freely in the reactor. The ‘Free model’ showed 100% ozone consumption, significantly higher than the 70% in the ‘Strainer model’, indicating better ozone accessibility and reactivity, and eliminating the need for ozone stripping in the off-gas, offering safety and cost benefits. Thermogravimetric and chemical analysis showed that the ‘Free model’ reduced lignin and impurities and increase holocellulose in the biomass, while increasing the streaming potential. This pretreatment significantly enhanced hydrolysis efficiency, achieving a 65% sugar yield, approaching the manufacturer’s theoretical maximum of the enzyme. In comparison, the ‘Strainer model’ and untreated samples yielded 40% and 43%, respectively. These results were corroborated by XRD and FTIR analysis. The increased surface area and direct ozone contact in the ‘Free model’ are key mechanisms driving these improvements. These findings suggest that the ‘Free model’ has the potential to serve as a more sustainable pretreatment method; however, further evaluation is needed, particularly in comparison to industrial-scale alternatives and their energy consumption, to fully assess its environmental impact.

Graphical abstract