We conducted hydrothermal liquefaction (HTL) of soybean oil, soy protein, microcrystalline cellulose, xylose, and lignin as individual compounds and binary, ternary, quaternary, and quinary mixtures at 350 °C for 30 min. The 34.5 wt % biocrude yield from HTL of the quinary mixture, which mimics the biochemical composition of swine manure, is much higher than the 21.5 wt % yield calculated from the weighted average yields from HTL of the individual components. HTL of binary mixtures of protein and cellulose, protein and xylose, cellulose and lignin, and xylose and lignin revealed synergistic effects on biocrude yield. On the other hand, HTL of soybean oil and lignin together exhibited an antagonistic effect on biocrude yield. These results from individual compounds and binary mixtures lead to a new model that can predict the yield, higher heating value, and C, H, and N content of biocrude from HTL of ternary, quaternary, and quinary mixtures of the biomolecules used in this study as well as in biocrude from HTL of different manures, algae, and lignocellulosic materials. The synergies identified in this work provide insights into strategies that could be employed in feedstock blending to improve biocrude yields and feedstock energy recovery from HTL of biomass resources.

Nitrogen flow and fate critically affects the hydrothermal liquefaction (HTL) of protein-rich feedstock such as livestock manure and algae. It also impacts the downstream process of HTL aqueous and oil products. Here, we reveal the migration and transformation pathways of nitrogen during HTL of typical livestock manures using combined gas chromatography–mass spectroscopy (GC-MS) and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Over 37% of nitrogen in the manure migrated to the aqueous phase in all HTL experimental trials, except for beef manure. GC-MS results indicated that the nitrogen compounds in the biocrude oil were mainly long chain amides, whereas in the aqueous phase the compounds were mainly small molecules of pyrazines, pyrroles, and pyridines. FT-ICR MS identified that N1O1, N2, and N2O1 species were dominant in the biocrude oil, while the nitrogen-containing compounds in the aqueous phase primarily took the form of N2O2 and N2O3. Five reaction pathways were proposed for the transformation of nitrogen during HTL. This study first characterized the transformation of nitrogenous compounds during HTL of livestock manures, which could be greatly beneficial to biocrude production, oil quality, and aqueous utilization in future studies.

Hydrothermal liquefaction (HTL) is a thermochemical process specifically suitable for treating wet wastes. This study investigated its potential for the production of biocrude oil and the recovery of nutrients and metals from human feces via HTL. Specifically, the effects of temperature (260 o C, 300 o C, 340 o C), retention time (10min, 30min, 50 min) and total solid (TS) content (5%, 15%, 25%) were studied. The maximum liquefied fraction was 87.89% and the highest biocrude yield reached 34.44%with a higher heating valueof 40.29 MJ/kg. Experimental results showed that 54% of carbon in the human feces was migrated to the biocrude oil while72% of nitrogen wasreleased to the aqueous phase. In addition, most of heavy and alkaline-earth metal elements in the human feces, including Ca (89%), Mg (81%), Al (88%), Fe (72%) and Zn (94%) were distributedin the solid residue, whereas K (89%) and Na (73%) were mainly dissolved into the aqueous phase.This study demonstrated thatthe efficient degradation of human waste via HTL without any pretreatment and its potential for the valorization in biocrude oil as well as separated nutrients and metals.

No abstract