An estimated 1.3 billion tons is wasted globally each year, which decompose in municipal landfills leading to both aquatic and air pollution. Hydrothermal liquefaction (HTL) is a process capable of breaking down unused food waste into carbon rich bio-oil, bio-char and residual aqueous phases. While the bio-char and bio-oil have valuable applications in soil amendment and transportation fuels respectively, the light organics that associate in the HTL water phase are unfavorable. Water soluble organics effectively reduce oil recovery and require costly downstream extraction for water purification. Therefore, it is desirable to reduce water soluble organic HTL products by catalytically shifting the product distribution into the oil phase. Homogenous alkaline catalysts have been previously reported to improve HTL oil yields but are also difficult to recover and recycle out of the wastewater stream. In contrast, heterogenous oxides can be easily separated and have been shown to promote coupling reactions that increase product molecular weight and hydrophobicity; thereby increasing total HTL oil yields by reducing water soluble hydrocarbons. Therefore, selection of a cheap and reusable catalyst would be desirable for an economical HTL process. In particular, red mud is considered a waste byproduct during alumina synthesis, making it a promising candidate as a HTL oxide catalyst. In our study, we evaluated the catalytic viability of cheap oxides during a food waste HTL upgrading process. We performed batch HTL reactions on representative consumer food waste at 300° C and 20.7 MPa using cheap and readily available oxide catalysts, such as quicklime, alumina and red mud. HTL oil, gas and solid product yields as well as each of their corresponding chemical properties were measured. Oil products were evaluated for their energy content using higher heating values (HHV) and oxygenated functionalities using infrared spectroscopy. In addition, total organic content of the aqueous phase product was determined using ICP-MS. Post-run characterization of both the heterogenous oxide and residual bio-char was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and temperature programmed oxidation (TPO). Preliminary results show that red mud improves total oil recovery relative to uncatalyzed HTL reactions by reacting water soluble organics.

Waste<sup>2</sup> to Energy Processing: HTL upgrading of food waste using inexpensive, alkaline waste catalysts

256th National Meeting (2018)

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Waste2 to Energy Processing: HTL upgrading of food waste using inexpensive, alkaline waste catalysts

Waste² to Energy Processing: HTL upgrading of food waste using inexpensive, alkaline waste catalysts