Recovery of value-added compounds through fast pyrolysis of apple pomace hydrochar

Authors: KAROD, MADELINE - Cornell University; ORTON, KELLENE - National Renewable Energy Laboatory; Elkasabi, Yaseen; Mullen, Charles; HARMAN-WARE, ANNE - National Renewable Energy Laboatory; IISA, KRISTIINA - National Renewable Energy Laboatory; GOLDFARB, JILLIAN - Cornell University

Submitted to: Journal of Analytical & Applied Pyrolysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Agricultural waste can be reused by converting it into valuable chemicals and materials. Liquefaction is a process by which that conversion happens using high temperatures in the presence of water. The products will include a solid carbon product (hydrochar), a bio crude oil, and some gases. The quality of hydrochar can determine if any further chemicals can be obtained from the char. This study examined how the quality of biochar and chemicals can be improved by further heating the biochar. In particular, apple pomace was converted into hydrochar and liquid chemicals. We found that removing chemicals stuck to the hydrochar is critical for obtaining more valuable chemicals, along with optimizing the liquefaction temperature.

Technical Abstract: Efforts to address the environmental challenges associated with agricultural waste have spurred interest in upcycling agro-industrial biomass via thermochemical conversion methods. Two such methods, hydrothermal carbonization (HTC) and pyrolysis, can be coupled to first reduce the water content of wet biomass wastes by producing a char via HTC and then produce a bio-oil via pyrolysis. However, HTC of biomass results in the formation of secondary char (SC), an amorphous tar-like mixture resulting from organic compounds released into the aqueous phase recondensing and polymerizing on the parent biomass. This study investigated how HTC temperature impacts the formation of SC from apple pomace and the SC’s subsequent impact on fast pyrolysis products. Hydrochars (HCs) were produced at temperatures of 175°C, 200°C, and 250°C. Lower HTC temperatures favor the formation of biorefinery platform chemicals such as 5-hydroxymethylfurfural and levulinic acid, while higher temperatures result in increased lignin degradation products (i.e., phenolics). HCs were subjected to fast pyrolysis before and after SC extraction in two analytical pyrolysis instruments. Fast pyrolysis of HC produced compounds similar to those found in SC, but with variations in CO and CO2 emissions. The combination of SC extraction and fast pyrolysis demonstrates promise for recovering value-added compounds from agro-industrial waste biomass while maintaining a solid char suitable for fuel and carbon management.