E. Pienihäkkinen: Thermochemical conversions of bio-mass residues to valuable fuels, chemicals and materials

Abstract: 

Actions to mitigate climate change require phasing out fossil raw materials in transportation as well as in the energy and chemical industries. However, finding cost‑effective alternatives to crude oil remains a challenge. One such alternative is bio‑oil produced through fast pyrolysis.

This dissertation examines fast pyrolysis as a method for converting lignocellulosic waste and side streams into liquid bio‑oils. The research focused particularly on the behaviour of different waste- and side-stream feedstocks in bench- and pilot‑scale fluidised‑bed processes, the effects of feedstock pretreatment, and the upgrading of bio‑oils.

The results showed that pretreatment can improve the yield and quality of bio‑oil, especially for feedstocks with high ash content, but overly intensive ash removal can reduce processability. Lignin‑rich side streams proved technically challenging, and their bio‑oil yields remained low.

In upgrading, it was found that gasification of bio‑oils is a technically viable and flexible method for producing synthesis gas from bio‑oils of varying quality. In addition, promising results were obtained in partially replacing fossil raw materials with bio‑oil in adhesive production.

Currently, industrial‑scale pyrolysis plants use relatively clean wood-based feedstocks. This research provides new insights into the processability of side‑stream-based biomasses and the potential of bio‑oils to replace fossil raw materials in the production of energy, chemicals, and materials.

Key words: fast pyrolysis, biomass, residues, waste, thermochemical conversion

Opponent: Prof. Frederik Ronsse, University of Ghent, Belgium

Custos: Prof. Ville Alopaeus, Aalto University School of Chemical Engineering

Link to electronic thesis: Thesis available for public display 7 days prior to the defence at Aalto University's public display page.

Link to the remote defense: LINK