(757b) Bifunctional Acid/Base Catalysis for Improved Biocrude Recovery from Food Waste Hydrothermal Liquefaction

Millions of tons of food waste are thrown into landfills annually and the resultant 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 and pressure to convert this waste into bio-crude. With appropriate upgrading, such as hydrodeoxygenation, 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 base catalysts are popular in HTL systems, however, pose process complexity and expense with separation and neutralization. Recently, solid catalysts, with bi-functional characteristics have been used successfully with in-situ upgrading of food waste to bio-oil. Hydroxyapatite (HAp) is a crystalline mineral found in bone and is an attractive catalyst due to its tuneable acid-base sites and potentially renewable sources. Six different synthesized and commercial HAp samples were screened for the highest oil yield. The commercial HAp-200 sample (200 nm particle size) resulted in an oil yield over 3 times greater than that of non-catalytic HTL. Commercial samples outperformed synthesized samples in all experiments. We have also tested and shown the crystalline structure of HAp to be stable for at least 100 hours, as verified through XRD and catalyst re-use.

In addition to improved oil yield, catalyst stability and economic feasibility are important factors in the success and future commercialization of food waste HTL. Through a technoeconomic analysis we produce a bio-crude with selling price < $3.00 (GGE).

Hydroxyapatite serves as a beneficial HTL catalyst by tripling oil yield and quadrupling energy recovery compared to non-catalytic experiments. This research serves to provide an economically promising process for the conversion of waste to a useful energy product by producing a bio-crude with competitively high yield and energy recovery.