International audienceThe upcoming depletion of fossil fuels calls for the development of alternative energies produced from renewable resources. Particularly, energy valorisation of agriculture and food processing wastes is one of the most promising tools for renewable energy production. The amount of food wastes is rapidly increasing due to urbanisation, industrialisation and population growth worldwide. They consequently represent a widely available resource, and their use as a raw material allows reducing the environmental cost associated with their disposal. These resources usually have high moisture content, making dry valorisation processes unattractive because of a costly drying step prior to conversion. Hydrothermal processes are conversely particularly well suited for the valorisation of wet organic wastes in an economical way, since they use water as the reaction medium. More specifically, liquid fuels can be produced using hydrothermal liquefaction (HTL). The process converts wet biomass into a crude-like oil with higher heating values up to 40 MJ/kg using subcritical water (T=250-370 degrees C, P=10-30 MPa). Though this is an active research area, the mechanisms of hydrothermal liquefaction still remain unclear today. Some processes have already been developed at the pilot scale for valorising food processing wastes. However, the development of HTL processes at industrial scales is facing technological and economic challenges. This paper discusses the two main issues to address for development of the process at large scales. On the one hand, hydrothermal conversion of food processing residues and model compounds is necessary to better understand the fundamentals of hydrothermal liquefaction. As well, technological and process integration issues have to be addressed to ensure economic viability of commercial HTL processes

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International audienceThere are many different ways to convert biomass into liquid fuels, mostly referred to as bio-oils. This paper presents the analysis of bio-oils produced by hydrothermal liquefaction and fast pyrolysis of beech wood. Both processes have a wide panel of parameters that can be optimised influencing the oil quality. Results of the analysis show that both oils have high acidities. Iodine values indicate a high degree of unsaturations. These two qualities seem to be inversely proportional in the case of pyrolysis oils. In the case of hydrothermal conversion, additives to adjust the pH such as sodium hydroxide increase oil yields, lower its viscosity but do little to further improve the quality of the oils. For pyrolysis oils, increasing the severity does reduce acidity but at the expense of more unsaturations and a loss in yield. The results show that without extensive upgrading or refining, commercial fuel standards cannot be met. Specific norms and standards are being elaborated for pyrolysis used in specific installations. This paper shows how detailed analysis can help to optimise process parameters with an objective that goes beyond the mass or energy yield. (c) 2016 Elsevier Ltd. All rights reserved