Combined Hydrothermal Liquefaction of Polyurethane and Lignocellulosic Biomass for improved carbon recovery

TL;DR

This study demonstrates an efficient hydrothermal liquefaction process for recovering carbon from polyurethane and biomass, achieving high energy and carbon recovery with a synergistic effect in co-liquefaction.

Contribution

It introduces a pilot-scale hydrothermal liquefaction method that enhances carbon recovery from polyurethane and biomass, with detailed analysis of the process efficiency and chemical composition.

Findings

Carbon recovery of 71% in oil phase.

Energy return ratio of 3.2.

Oil rich in nitrogen heteroaromatics and polyols.

Abstract

Due to the high versatility of Polyurethane (PUR), its share amongst synthetic polymers to manufacture consumer goods is increasing. This study proposes, tests and validates through pilot processing a highly efficient method for carbon recovery of PUR and in the form of an oil phase concentrated in carbon using hydrothermal liquefaction (HTL). Hot liquid water mixed with PUR residues and a lignocellulosic material (two species of Miscanthus) were treated at subcritical water temperatures, generating an oil-phase rich in hydrocarbons. A high synergistic effect in the co-liquefaction was observed, leading to a carbon and chemical energy recovery to the oil of 71 and 75% respectively. Pilot plant processing, using optimized process parameters, yielded a total process efficiency, accounting heating utilities, of 61%, resulting in a 3.2 ratio of energy return over investment. Using spectroscopic and high-resolution mass spectrometry analysis the oil revealed a high content of nitrogen hetero aromatic and polyol compounds. The high synergy observed for the co-liquefaction of PUR and miscanthus is attributed to recombination of synthetic and biological materials, specifically due to aromatics present in the media and nitrogen-containing compounds recombination. The results show that HTL can be an efficient method for carbon recovery of PUR aided by biomass.