In x-ray photoelectron spectroscopy (XPS), knowledge of elemental depth distributions within the first 10 nm is often essential. However, none of the conventional XPS methods can reliably discern, for example, a thin overlayer from clusters on rough surfaces. Therefore, reliable experimental data on the actual distributions of lignin and extractives on the fibre surfaces is needed, although there are numerous XPS studies on cellulosic fibres and paper.We have studied surface distributions of organic compounds on natural cellulosic fibre materials (cotton, flax and softwood pulps) with XPS, using a novel approach introduced by Tougaard. We were able to model the surface composition of rough fibre surfaces via simple spectral analysis of the O 1s signal. The simple spectral background analyses used show that in the case of cotton and flax, the non-cellulosic compounds cover the cellulosic fibre surface much more effectively than in softwood pulps, in spite of the smaller amount of non-cellulosic material present.
Biomass is a promising alternative for the production of energy, novel materials, chemicals, and other valuable products. A certain degree of processing is required to achieve those results. Hydrothermal processes offer a unique way to obtain a wide range of biorefinery products. They can be considered as environmentally friendly processes, using solely water at different temperatures as a process medium to convert abundant and inexpensive biomass into products. We provide a short overview on hydrothermal processes that use water in its liquid state, including hot water extraction, pressurized hot water extraction, liquid hot water pretreatment, hydrothermal carbonization, and hydrothermal liquefaction. We also provide examples of current research and realworld findings. We then present a novel hydrothermal biorefinery concept for sequencing these single processes, giving concrete examples of possible raw materials and products. Sequencing gives new possibilities for biorefineries to exploit all the biomass components as valuable products with zero losses. The added value comes from the increased efficiency of the bio-based products’ value chain, by reducing losses and generating higher-value products and services.
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