Pyrolysis of biomass to produce liquid fuel and chemicals has been considered as an alternativeto fossil fuel because biomass has a lower environmental impact; moreover, it is renewable andcould be sustainable. However, the process of bio-oil production involves a series of complexchemical reactions which are dependent on the biomass feedstock and composition,temperature, heating rate as well as residence time. In this thesis, pyrolysis was carried out in amicro-pyrolyser connected to a gas chromatograph with a mass spectrometer/flame ionisationdetector to separate and identify the formed volatile compounds.

Firstly, the influence of temperature and residence time on the primary product yield andmechanistic pathways was investigated for the pyrolysis of cellulose, xylan and lignin attemperatures ranging between 400 – 600°C and residence times between 0.5 – 5 s. The resultshowed a general increase in the yield (count/μg sample) for most of the volatile compoundswith increasing temperature and residence time. Additionally, the interaction between theindividual biomass components was investigated. A comparison of the experimental andpredicted results showed that the product yields for some of the volatile compounds wereinhibited, especially for the cellulose-xylan-lignin blend and the native birch wood. This maybe due to the chemical interaction between the biomass and the presence of inorganic materials.The co-pyrolysis of palm kernel shell (PKS), mahogany (MAH) and iroko (IRO) sawdustshowed that the yield of the volatile compounds is dependent on the biomass composition andblend ratio. The co-pyrolysis of PKS, MAH and IRO in equal proportions showed an increasedrelative yield of the sugars compared to the other blend ratios investigated. Finally, the effectof dilute acid pretreatment on PKS, MAH and IRO sawdust prior to fast pyrolysis wasinvestigated. The removal of inorganic materials leads to increased yield, especially the sugarsand the furans. These results are important for understanding the formation mechanism of thepyrolysis products, selection of relevant operating conditions and the selection of a suitablemethodology that could enhance the pyrolysis product yield.

Fast co-pyrolysis (FCP) of wood and plastic offers a promising strategy not only to reduce dependence on fossil fuels for feedstock and chemical production but also to mitigate plastic waste accumulation. This thermochemical process decomposes wood and plastic in the absence of oxygen. It involves complex chemical reactions that yield valuable solid, liquid and gaseous products. These reactions include both primary and secondary reactions. However, limited research has been conducted on gases produced during primary reactions. In this work, micropyrolyser connected with a gas chromatography, a mass spectrometry, a flame ionization detector, and a thermal conductivity detector (Py-GC/MS/FID/TCD) have been employed to analyse gaseous products from primary reactions during both non-catalytic and catalytic FCP of wood and plastic.

Primary gaseous products from the fast pyrolysis of cellulose, xylan, and lignin were successfully promoted, showing increased gas yields at higher temperatures and longer residence times. Additionally, fast pyrolysis of low-density polyethylene (LDPE), polypropylene (PP), and polystyrene (PS) has been performed. Fast pyrolysis of lignocellulosic biomass primarily produces oxygenated compounds such as sugars, phenols, carboxylic acids, aldehydes and ketones. Meanwhile, fast pyrolysis of plastics yields aliphatic and aromatic hydrocarbons, including alkanes, alkenes and alkynes. The underlying reaction mechanisms for primary reactions were proposed.

The evaluation of gaseous products from the pyrolysis of individual materials was further used to assess interaction effects during FCP of birch wood with plastics (Wood-LDPE, Wood-PP, and Wood-PS). Significant interactions were observed, with a 90% reduction in oxygenate content in the gases at 75 wt% wood content, regardless of plastic type. Furthermore, catalytic FCP using calcium carbonate (CaCO₃) was conducted to explore the role of in-situ catalysts in enhancing gas yield. Adding 10 wt% CaCO₃ doubled the total gas yield, with a significant increase in volatile compounds containing fewer than 10 carbon atoms.

The findings contribute to optimising fuel and chemical production by fine-tuning the wood-to-plastic ratio and selecting appropriate plastic types.