Decarbonizing paper mill sludge waste into micro and nanofibrillated cellulose via enzyme hydrolysis and dual asymmetric centrifugation

Abstract

The production of micro- and nano-fibrillated cellulose (MNFC) from paper mill sludge (PS) using simple enzymatic and mechanical treatments has been evaluated for their performance as value-added materials in packaging and other applications. Sludge from a US paper mill was analyzed for the viability of this conversion process. The enzymatic treatment was conducted at variable concentrations using an enzyme cocktail of exoglucanase and endoglucanase, followed by mechanical dual asymmetric centrifugation (DAC) treatment. The presence of inorganics and lignin facilitated the mechanical defibrillation of the fibers, making the MNFC production more energy-efficient. The prepared MNFC was characterized for fibrillation, charge, crystallinity, and surface morphology. Scanning electron microscopic (SEM) images show the highly fibrillated MNFC and the distribution of inorganic nanoparticles on the fiber surface. The X-ray diffractometric (XRD) analysis shows 44–65 % crystallinity. Furthermore, MNFC-based films derived from PS demonstrated excellent strength and flexibility, making them suitable for packaging and other applications. Overall, this conversion approach can save the paper industry millions of dollars in disposal costs while upcycling waste and reducing greenhouse gas (GHG) emissions associated with waste streams.