Development of new technologies for valorization of forest resources – from molecules to plant

Today's world is very dependent on fossil feedstock to produce energy and various chemical, pharmaceutical and alimentary products which have a dire consequence on our daily life. Using renewal feedstocks such as wood- based biomass can be an attractive solution, especially in countries with high forest coverage such as Finland.

Many valorization technologies for forest resources have been tested and put to test. In this work, the focus has been on the oxidation of the monomeric sugar arabinose, which originates from the hydrolysis of the arabinogalactan hemicellulose which appears in the Larix sibirica tree that is quite abundant in the northern hemisphere. The main aim of this work has been to develop a novel and integrated methodology for the valorization of Northern forest resources, starting from laboratory scale experiments and progressing towards large scale plant design. Firstly, a general dynamic model for multiphase reactor systems was developed and implemented using gProms software. After this stage, laboratory scale experiments of selective arabinose oxidation to arabinonic acid were performed to estimate and adjust the model parameters, mainly the gasliquid mass transfer coefficient in the three-phase loop reactor filled with gold catalyst extrudates.

The model results showed that the size and shape of the catalyst extrudates are impacting the conversion of arabinose, but this effect can be tackled by using longer reactor. Therefore, the research was focused afterwards on testing these findings experimentally by using the reactor and screening higher liquid flowrates, which confirmed these observations. It was noteworthy that another advantage of using such a reactor system is the pH control which is an important parameter in the selective catalytic oxidation of sugars.

Techno-economic analysis (TEA) was performed based on previously published experiments and kinetic results. At the first stage, two processes (with and without heat recovery) were designed using Aspen Plus software. Based on the simulation results, the economic analysis was performed. It was found that even though applying heat recovery causes additional capital costs but in the long term it is more profitable due to suppressed operating costs. Also an essential part of the operating costs come from the raw material costs, mainly the arabinose, which emphasizes the importance of the optimization of the arabinogalactan extraction process from Larix sibirica.

Finally, the findings can be extrapolated for other applications such as in the hydrogenation of sugars or production of furfural. Also the designed process results can be used to analyze the environmental impacts of the process the using the life cycle assessment (LCA) methodology to understand more the environmental hotspots and thus orienting towards the next research steps.