The Faculty of Applied Engineering has a new doctor! Dr. Giorgio Tofani defended his doctoral thesis on the 13th of January, with professor Serge Tavernier and professor Iris Cornet as promotors. The doctoral thesis is titled ‘Biorefinery concept in paper recycling: modelling, verification and prediction of bleaching process'.

The fibres from recycled paper are mainly used to produce newsprints, magazines and packaging materials. Depending on the application of the paper product, the fibres must have different properties (e.g. length and brightness). For example, newsprints require a particular level of brightness. The typical industrial process step to reach such brightness is called bleaching.

Nowadays, the composition of recycled paper is changing because our lifestyle is changing. We are reading fewer newspapers, and e-commerce is increasing. So, the demand for packaging products for deliveries is increasing. Therefore, low-quality fibres, which are more difficult to bleach, will have to be used for newsprint production.

The paper recycling industry also generates several waste streams that are currently either recirculated in the process, converted to low-value products or disposed of in a landfill.

This doctoral work focused on two targets:

• Understand the differences between the fibre types to the bleaching process and develop a mathematical equation to estimate the brightness of a recycled paper when its amount and types of fibres are known. In this way, it would be possible to predict the bleachability of a sample of recovered paper.
• Recover chemicals and materials from two waste streams generated respectively during paper recycling and cardboard recycling.

​Conclusions

The different fibre types have diverse reactivity to the bleaching process, and they mutually influence each other during this treatment. A mathematical equation, called multiple linear regression, was developed and permitted to estimate the brightness knowing the fibre composition of recovered paper. More research can be considered to improve the mathematical equation.

Recycled filler, a mixture of salts and clays, was recovered from the waste generated during paper recycling. This material can be recycled and used in papermaking. Moreover, two chemical compounds (lignin and hydrocarbon derivatives) were retrieved from the waste generated during the recycling process of cardboard. These chemicals have a wide range of applications. For example, lignin can be used in the asphalt industry.