Carbonaceous soot has been generated from pine in a range of appliances to simulate different combustion conditions. The fuel as well as biomass cell wall components have been studied by pyrolysis-GC-MS and pyrolysis-GC-TCD. In addition, the soots have been probed using both pyrolysis-GC-MS and direct inlet mass spectrometry (DI-MS). The material collected from the pine combustion is smoke, and the major component is a carbonaceous soot. The soots contain both organic carbon (adsorbed species) and black (solid) soot, and the organic carbon consists of primary pyrolysis products from the cell wall components, as well as decomposition products, PAH and oxidized PAH. The black carbon contains oxygen functionality (of the order of 5-10 wt % O), and there are indications that this is incorporated during soot growth, although surface oxidation on reactive sites could also be important. The decomposition products suggest an important additional PAH route is via cyclopentadiene, which is derived after cracking of lignin monomer fragments. Kinetic modeling also highlights the lignin monomers as important contributions to the soot production pathways. A model is proposed which, in addition to the hydrogen abstraction carbon addition (HACA) mechanism, incorporates the cyclopentadiene and the O-PAH addition routes to soot.

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This paper reports work that compares slow pyrolysis and MW pyrolysis of two different feedstock (willow chips and straw), with particular focus on physical properties of resulting chars and their relation to biochar soil function. In these experiments, slow pyrolysis laboratory units at the University of Edinburgh and the MW pyrolysis units at the University of York were used to produce biochar from identical feedstock under a range of temperatures. Physical properties and stability of thus produced biochar from both systems were then analysed and compared. The results showed that using MW, pyrolysis can occur even at temperatures of around 200 °C, while in case of conventional heating a higher temperature and residence time was required to obtain similar results. This paper presents new data not only on the comparison of biochar from microwave and slow pyrolysis in terms of physical properties, but also in respect to their carbon sequestration potential, i.e. stability.

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