How can industry produce more sustainable packaging materials without increasing energy consumption? This is one of the questions explored by Björn Öman in his Licentiate thesis on the production of greaseproof paper, a grease-resistant paper used in applications such as food packaging.
Greaseproof paper, used for products such as baking parchment and muffin cases, is increasingly regarded as an attractive alternative to plastic-based packaging materials. However, achieving its grease-resistant properties requires intensive refining of the paper fibres, making the material difficult to dewater during production. As a result, the manufacturing process is highly energy-intensive.
In his research, Björn Öman investigated how production efficiency can be improved through two different strategies: enhanced vacuum dewatering and optimised fibre composition.
Progressive vacuum dewatering improved water removal
One part of the research focused on so-called progressive vacuum dewatering, in which the vacuum level is gradually increased as the paper becomes increasingly difficult to dewater. This is particularly relevant for greaseproof paper, as the heavily refined fibres form a very dense structure that makes it challenging to remove water during production.
Laboratory trials showed that a gradual increase in vacuum pressure resulted in a higher solids content in the paper, indicating the potential for more efficient dewatering.
"As water is removed, the fibre structure of the paper becomes increasingly dense, making it more difficult to extract the remaining water. By adjusting the vacuum level according to the progress of the dewatering process, we were able to improve water removal. This demonstrates that it is not only the level of vacuum that matters, but also when it is applied," says Björn Öman.
Eucalyptus fibres reduced energy demand
The second part of the study examined how different fibre compositions affect the production process. By incorporating eucalyptus fibres into conventional softwood pulp, the energy required for refining could be reduced by approximately 164 kWh per tonne of pulp, while maintaining the grease barrier properties of the paper.
The findings indicate significant potential to reduce energy consumption without compromising the performance requirements of food packaging materials.
"The interesting finding is that by adjusting the fibre composition, we were able to substantially reduce the energy required for refining while maintaining the properties needed to create a dense paper structure. This shows that there are opportunities to improve production efficiency without compromising paper quality," says Björn Öman.
Contributing to more sustainable packaging
The thesis demonstrates that combining improved dewatering with optimised fibre composition can contribute to a more resource-efficient production of greaseproof paper.
