Hydrothermal valorization via liquid hot water and hydrothermal carbonization of pea pod waste: Characterization of the biochar, and quantification of platform molecules.

Abstract

The cultivation of pea pods spans across various regions and climates with a global production of around 20 million tons. The pea peel wastes, which make up 30–40% of the total weight of the peas, are freely available in large quantities. The biomass used was characterized via ultimate, proximate, and structural analysis obtaining a 20,2 %w of cellulose and 17,4 %w of hemicellulose which via valorization processes can be transformed into platform chemicals. Hydrothermal valorization presents itself as a clean form of treatment of said wastes, ranging from 120 – 180 ºC (LHW) to 180 to 260 ºC (HTC). The use of LHW can lead to the production of sugars (up to 70%w yield) and levulinic acid (4 %w yield) while the use of HTC leads to Formic acid (40 %w) and levulinic acid (4 %w yield). The use of LHW for longer times favors the production of HMF and Furfural. The use of homogeneous catalysts (H2SO4, CH3COOH, KOH and NaHCO3) was implemented and their selectivity described. Solid fractions of LHW and HTC were characterized via FTIR and elemental analysis and the change in their structure described as they shift from biomass to biochar. Optimal conditions for each platform chemical were reported for best utilization of the peapod waste.