Innovation in lignocellulosics dewatering and drying for energy sustainability and enhanced utilization of forestry, agriculture, and marine resources - A review

Synergistic cell-free enzyme cocktails for enhanced fiber matrix development: improving dewatering, strength, and decarbonization in the paper industry

BACKGROUND

The pulp and paper industry is under increasing pressure to adopt sustainable solutions that address its substantial energy consumption and environmental impact. One of the most energy-intensive operations is the thermal drying, which presents significant opportunities for efficiency improvements. This study evaluates a cell-free mild enzyme pretreatment, utilizing a cocktail of cellulases and xylanases, combined with cationic starch, to enhance dewatering efficiency and improve paper strength utilizing bleached hardwood pulp fibers. Life cycle and economic analysis were also conducted to quantify the environmental impact and economic benefits, with a particular focus on direct greenhouse gas emissions. Enhanced water removal during pressing can significantly reduce energy consumption during thermal drying, facilitating the decarbonization of the paper industry.

RESULTS

The cell-free enzyme pretreatment, applied with mild refining and cationic starch, achieved significant improvements in dewatering efficiency and paper strength. The treatment led to an 11% point increase in solids and a 25% improvement in tensile strength. Morphological analyses revealed no changes in fiber length and width; however, reductions in kink and curl indexes indicated enhanced fiber flexibility and bonding potential. Furthermore, the enzyme-starch combination decreased water retention value by 27%, including substantial reductions in bound and hard-to-remove water content. Environmental assessments estimated a 12% reduction in global warming potential (GWP), with the technology yielding net savings of $11.29 per air-dried ton of paper through reduced natural gas consumption.

CONCLUSIONS

This study demonstrates the technical feasibility and economic viability of incorporating enzyme and cationic starch treatments into papermaking. The treatment improves paper quality while reducing energy consumption, costs, and carbon emissions. These findings support the broader adoption of enzyme-based innovations for sustainable manufacturing, aligning with decarbonization goals and industry demands for greater efficiency. The results highlight a promising avenue for achieving significant environmental and economic benefits in the pulp and paper sector.

Elucidation of temperature-induced water structuring on cellulose surfaces for environmental and energy sustainability

Optimizing drying energy in the forest products industry is critical for integrating lignocellulosic feedstocks across all manufacturing sectors. Despite substantial efforts to reduce thermal energy consumption during drying, further enhancements are possible. Cellulose, the main component of forest products, is Earth's most abundant biopolymer and a promising renewable feedstock. This study employs all-atom molecular dynamics (MD) simulations to explore the structural dynamics of a small Iβ-cellulose microcrystallite and surrounding water layers during drying. Molecular and atomistic profiles revealed localized water near the cellulose surface, with water structuring extending beyond 8 Å into the water bulk, influencing solvent-accessible surface area and solvation energy. With increasing temperature, there was a ∼20 % reduction in the cellulose surface available for interaction with water molecules, and a ∼22 % reduction in solvation energy. The number of hydrogen bonds increased with thicker water layers, facilitated by a "bridging" effect. Electrostatic interactions dominated the intermolecular interactions at all temperatures, creating an energetic barrier that hinders water removal, slowing the drying processes. Understanding temperature-dependent cellulose-water interactions at the molecular level will help in designing novel strategies to address drying energy consumption, advancing the adoption of lignocellulosics as viable manufacturing feedstocks.