(721b) Hydrothermal Liquefaction of Model Polysaccharides and Polysaccharide-Rich Food-Processing Waste

Hydrothermal liquefaction (HTL) is the thermochemical conversion of wet biomass (e.g., food waste, waste from food processing industries) in hot compressed water into energy-dense biocrude, a biofuel precursor. This process is especially attractive for wet biomass as it obviates the drying step required in other biomass conversion processes (e.g., pyrolysis). The main biochemical constituents of food waste are proteins, polysaccharides, and lipids, and the biocrude yields from HTL can be correlated with and predicted from its biochemical content. Previous studies with HTL of model biomass compounds revealed that polysaccharide is the most recalcitrant biochemical constituent to obtain biocrude^3-5.

Conventional HTL of various agricultural and food processing wastes has been studied extensively under subcritical temperatures isothermally for long holding times^1-2. Fast HTL, a recent variation of this technology involves rapid non-isothermal heating and short reaction times (~1 min) and has achieved higher biocrude yields than conventional HTL for a variety of whole biomass^6-11 and a few proteins^12-13.

Here we will focus on fast and isothermal HTL at different biomass loadings of model polysaccharides (chitin, pectin, potato starch), and processing waste obtained from a potato flake production plant. Using knowledge of the structure of and components in the model polysaccharide and temporal variation of the reaction products, we can posit reaction pathways and determine the reaction kinetics. Such information will provide new knowledge about the hydrothermal chemistry of polysaccharides that have received scant attention despite their abundance in food waste. We will further use the results from model polysaccharides to interpret the HTL reaction pathways of the potato flake processing waste. These results can facilitate the assessment of the potential of HTL for producing bio-fuel precursors from any polysaccharide-containing food/food-processing waste.

References:

1. Pavlovic, I.; Knez, Z.; Skerget, M., Hydrothermal reactions of agricultural and food processing wastes in sub- and supercritical water: a review of fundamentals, mechanisms, and state of research. J Agric Food Chem 2013, 34, 8003-25.
2. Déniel, M.; Haarlemmer, G.; Roubaud, A.; Weiss-Hortala, E.; Fages, J., Energy valorisation of food processing residues and model compounds by hydrothermal liquefaction. Renewable and Sustainable Energy Reviews 2016, 1632-1652.
3. Biller, P.; Ross, A. B., Potential yields and properties of oil from the hydrothermal liquefaction of microalgae with different biochemical content. Bioresour Technol 2011, 1, 215-25.
4. Teri, G.; Luo, L.; Savage, P. E., Hydrothermal Treatment of Protein, Polysaccharide, and Lipids Alone and in Mixtures. Energy & Fuels 2014, 12, 7501-7509.
5. Posmanik, R.; Cantero, D.; Malkani, A.; Sills, D.; Tester, J., Biomass conversion to bio-oil using sub-critical water: Study of model compounds for food processing waste. The Journal of Supercritical Fluids 2017, 26-35.
6. Faeth, J. L.; Valdez, P. J.; Savage, P. E., Fast Hydrothermal Liquefaction of Nannochloropsis sp. To Produce Biocrude. Energy & Fuels 2013, 3, 1391-1398.
7. Hietala, D. C.; Faeth, J. L.; Savage, P. E., A quantitative kinetic model for the fast and isothermal hydrothermal liquefaction of Nannochloropsis sp. Bioresour Technol 2016, 102-11.
8. Valdez, P. J.; Nelson, M. C.; Faeth, J. L.; Wang, H. Y.; Lin, X. N.; Savage, P. E., Hydrothermal liquefaction of bacteria and yeast monocultures. Energy & Fuels 2013, 1, 67-75.
9. Bach, Q.-V.; Sillero, M. V.; Tran, K.-Q.; Skjermo, J., Fast hydrothermal liquefaction of a Norwegian macro-alga: screening tests. Algal Research 2014, 271-276.
10. Zhang, B.; von Keitz, M.; Valentas, K., Thermal effects on hydrothermal biomass liquefaction. Applied Biochemistry and Biotechnology 2008, 1-3, 143-150.
11. Qian, L.; Wang, S.; Savage, P. E., Hydrothermal liquefaction of sewage sludge under isothermal and fast conditions. Bioresource technology 2017, 27-34.
12. Sheehan, J. D.; Savage, P. E., Products, Pathways, and Kinetics for the Fast Hydrothermal Liquefaction of Soy Protein Isolate. ACS Sustainable Chemistry & Engineering 2016, 12, 6931-6939.
13. Sheehan, J. D.; Savage, P. E., Molecular and Lumped Products from Hydrothermal Liquefaction of Bovine Serum Albumin. ACS Sustainable Chemistry & Engineering 2017, 5, 10967– 10975.