Hydrothermal liquefaction of waste biomass model compounds. a study to unravel the complexity of Interactions in biocrude production from mixtures of cellulose-albumin-lipids

Hydrothermal liquefaction is a promising technology for liquid biofuel production from a wide range of organic wastes. Waste biogenic feedstocks with a high moisture content are particularly suitable for this purpose due to the possibility to feed wet materials and to obtain high liquid yields in hydrothermal liquefaction (HTL). Although, yields and quality of the obtained liquid products are usually strongly dependent on the composition of the feedstocks, and due to their variability, it is often difficult to have reliable predictions. However, biogenic waste can be easily schematize based on their content of organic macro-components, mainly polysaccharides, proteins, and lipids. This work tries to summarize the effect of the variation of feedstock’s composition on yields and the quality of HTL products, with a particular focus on binary interactions between the macro-components. Cellulose, egg albumin and sunflower oil are used as model compounds to represent polysaccharides, proteins, and lipids, respectively. HTL tests are carried out in micro autoclaves of 10 mL using these model compounds alone and in binary and ternary mixtures as feedstocks, at 330°C and 10 minutes of retention time. Results showed that the biocrude yields did not follow the behaviour predicted by the linear combination of the three compounds but an increase of biocrude production and a reduction of solid residue is obtained for the mixtures. GC-MS results showed the presence of compounds related to Maillard reactions and amides formation. Some general reaction pathways were summarized to explain these results. The comprehension of these interactions can guide the future research to obtain a prediction model for biofuel production through a HTL process.