Food Waste to Energy: Leveraging Catalytic Hydrothermal Liquefaction

Millions of tons of food waste are thrown into landfills annually.[1] Degradation products lead to a variety of detrimental wastes. Hydrothermal liquefaction (HTL) is an emerging technology in the waste-to-energy field that utilizes high temperature (T=300 ̊C) and pressure (P=3000 psi) to convert this waste into a bio-oil. With appropriate in-situ or downstream upgrading, this oil is suitable for the transportation and heating industries. HTL’s benefit is using complex, high water content feedstocks without inefficient drying steps.

Homogeneous catalysts have been utilized with HTL, however, pose process complexity and expense with separation and neutralization. Recently, solid catalysts, with acid- base characteristics have been used successfully with in-situ upgrading of food waste to bio-oil. [2,3]. Hydroxyapatite is a crystalline mineral found naturally in bones and makes an attractive catalyst due to its tunable acid-base sites and potentially renewable sources. This relatively inexpensive catalyst has preliminarily shown to result in the highest oil yield from food waste. In this work, a near supercritical liquid phase reactor is used with a food waste/catalyst slurry to drive the complex reactions. A bio-oil is generated with higher heating values approaching the range of diesel fuel and the catalyst shows excellent hydrothermal stability and regeneration. Additionally, discussion of producing bio-oil in a flow-based system will be discussed.