# Valorization of Spruce Bark to Environmentally Sustainable Packaging Materials

## TL;DR

This study explores using spruce bark to create eco-friendly packaging materials with improved strength and UV protection.

## Contribution

The novel approach is using spruce bark extractives to coat cellulose films, enhancing their hydrophobicity and mechanical properties.

## Key findings

- Coated films showed increased water contact angles and UV-shielding properties.
- MFC-coated films achieved a tensile strength of 119 MPa, comparable to common packaging materials.
- Valorization of spruce bark reduced environmental impact compared to incineration.

## Abstract

In this study, cellulose-based
films were developed by using microfibrillated
cellulose (MFC) and lignin-containing microfibrillated cellulose (Lig-MFC)
derived from sequentially extracted spruce bark. The films were coated
with the hydrophilic extractives from the fractionation, resulting
in additional MFC-coated and Lig-MFC-coated cellulose films. A combination
of morphological (AFM), surface (water contact angle (WCA), roughness),
optical (UV–vis), and mechanical properties was analyzed to
assess structure–property relationships. Coated films exhibited
significantly enhanced hydrophobicity and UV-shielding, with WCA increasing
from 47° to 76° for MFC and from 66° to 71° for
Lig-MFC. Notably, MFC-coated films displayed superior mechanical performance,
with a tensile strength of 119 MPa and elongation of 11%, surpassing
most lignocellulosic-based films in the literature derived from bark.
In addition, this tensile strength falls within or above the range
of commonly used materials, such as kraft liner, PET, and LDPE, suggesting
realistic opportunities for substitution in short-lived packaging
applications. AFM analysis revealed a reduction in surface roughness
after coating, correlating with an enhanced WCA. Compared with similar
biobased films in the literature, the extractive-coated MFC films
show superior performance in terms of strength, flexibility, and UV-shielding
properties. This valorization route offers both economic and environmental
sustainability advantages compared with incineration for energy recovery.
A comparative life cycle assessment (LCA) study showed that valorization
of the pulp and hydrophilic extractives from the bark biorefinery
into different qualities of MFCs gave substantial climate change benefits
stemming from the possibility of substituting packaging materials
with high inherent environmental impact.