Characterization of products from catalytic hydrothermal carbonization of animal manure

Authors: QARAMALEKI, SAEED - University Of Nevada; CARDENAS, JOSE - University Of Nevada; Jackson, Michael - Mike; Compton, David - Dave; Szogi, Ariel; Ro, Kyoung; CORONELLA, CHARLES - University Of Nevada

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2023
Publication Date: 8/25/2023
Citation: Qaramaleki, S.V., Cardenas, J., Jackson, M.A., Compton, D.L., Szogi, A.A., Ro, K.S., Coronella, C.J. 2023. Characterization of products from catalytic hydrothermal carbonization of animal manures. Agronomy Journal. 13(9):2219. https://doi.org/10.3390/agronomy13092219.
DOI: https://doi.org/10.3390/agronomy13092219

Interpretive Summary: Hydrothermal carbonization (HTC) uses water as the reaction medium to convert wet organic residues to carbon-rich solid and liquid products. The solid product called hydrochar can be used as a fossil coal alternative, soil amendment to improve soil quality, and increase soil carbon. It can also be used as adsorbents to remove pollutants from water or gases. The liquid product can be used to produce biogas via anaerobic digestion. This paper presents hydrothermal carbonization (HTC) of cow and pig manures using sulfuric and acetic acid as catalysts and compares the results with HTC done without acid catalyst. HTC experiments have been carried out at 170 degree Celsius (°C) for 10 min. Based on our observation acid catalysts increased the carbonization and produced hydrochar with higher energy contents. Sulfuric and acetic acids both increased leaching of the inorganic minerals. Phosphorus leaching was increased with acid catalysts as well. The phosphorus contents of pig manure and its HTC liquid product were an order of magnitude above those of cow manure. Nitrogen extraction was barely affected by acetic acid and even decreased for pig manure. On the other hand, sulfuric acid not only increased nitrogen hydrothermal leaching for both types of manure, but also enhanced the relative ammonia fraction. The results of this study showed that sulfuric acid catalyst can be used to extract nutrients such as nitrogen and phosphorus from animal manure while producing value-added hydrochar.

Technical Abstract: This paper presents hydrothermal carbonization (HTC) of cow and pig manure under sulfuric and acetic acid as catalysts and compares the results with HTC done without acid catalyst. HTC experiments have been carried out at 170 degree Celsius (°C) for 10 min and the concentration of acids was 0.3 molarity (M). Based on our observation acid catalysts increased the carbonization thus energy densification for both types of manure with sulfuric acid having the most significant impact. Sulfuric and acetic acids both increased leaching of the inorganic minerals such as calcium (Ca), potassium (K), magnesium (Mg), iron (Fe) albeit with varying degrees. Phosphorus leaching was increased with acid catalysts as well. The results confirmed above 90% conversion of total phosphorous to phosphate in hydrothermal condition. The phosphorus contents of pig manure and its HTC liquid product were an order of magnitude above those of cow manure. Nitrogen extraction was barely affected by acetic acid and even decreased for pig manure. On the other hand, sulfuric acid not only increased nitrogen hydrothermal leaching for both types of manure, but also enhanced the relative ammonia fraction. Further analysis of the aqueous products signified the formation of acetic acid, furfural and 3-aminopyrazine 1-oxide compounds for sulfuric acid catalyzed hydrothermal treatment of both types of manure. Analysis of the residual gas confirmed trace amount of hydrogen sulfide (H2S), nitrogen dioxide (NO2) and sulfur dioxide (SO2) formation. Addition of sulfuric acid increased the NO2 significantly. Finally, detailed mass balances of the carbon and macro nutrients are presented.