Strategic way for valorization of manure into chemicals and fuels

Animal manure contains a variety of organic materials that can be used for synthesis of value-added biofuels and chemicals. To maximize the carbon recovery from animal manure waste, this study focused on consecutive valorization of horse manure into furfural and syngas (H₂ and CO). Acid hydrolysis/dehydration of horse manure was employed to extract furfural, and the residue after furfural extraction was valorized into syngas and bio-oil through CO₂-assisted pyrolysis. In acid treatment process, the levulinic acid and furfural were produced from horse manure, and the maximum yield (3.68 wt%) of furfural was achieved at 0.5 M H₂SO₄ (40 wt% based on hemicellulose content). Horse manure residue was further converted into bio-oil and syngas under N₂/CO₂ environments. Under CO₂ atmosphere, gas phase homogeneous reactions were occurred, which simultaneously reduced CO₂ and oxidized bio-oil showing enhanced CO formation (18 times higher comparing to pyrolysis under N₂). The homogeneous reaction also resulted in decrease of aromaticity in bio-oil. To enhance the reaction kinetics of the homogeneous reaction and thermal cracking of bio-oil under CO₂, catalytic pyrolysis was performed in the presence of Ni/SiO₂ catalysts. The catalytic pyrolysis improved syngas (H₂ and CO) production more than one order of magnitude higher, comparing to pyrolysis without Ni catalyst. All the experimental findings suggested that horse manure and CO₂ could be used as raw materials for production of value-added chemicals and syngas. Copyright © 2021 Elsevier Ltd. All rights reserved.