Hydrothermal processes to recover energy and nutrients from liquid portion of swine manure

An integrated method for treatment of animal manure has been proposed in Environment-Enhancing Energy (E2-Energy) lab. This study aimed at evaluating the feasibility of recovering the energy and nutrients from the liquid portion of animal manure (LPAM), via physical and biological concentration and hydrothermal processes. First, LPAM was concentrated physically through evaporation for hydrothermal processes, including hydrothermal liquefaction for biocrude oil production, and catalytic hydrothermal gasification for biogas production. Related analyses and estimations for energy and nitrogen recovery revealed that HTL was unable to transform successfully the organics in the cLPAM into biocrude oil, as the highest biocrude oil yield was only 8.25% of volatile solids at 300 degree C/60 min, recovering 19% of the original energy in the LPAM. On the other hand, CHG demonstrated a higher energy recovery of 149% under 600 degree C/60 min into the biogas product, and was able to remove 96% of the COD. CHG also had higher nitrogen recovery efficiency, and could possibly convert nitrogen gas into ammonia under the studied conditions. Second, high organic content in the liquid swine manure was concentrated using bioreactor for biomass cultivation. The cultivated biomass was high in protein and fiber, but lacking lipid. The biomass was treated by hydrothermal liquefaction (HTL) for biocrude oil production, but the post HTL wastewater (PHWW) was still high in organics, thus a secondary process of catalytic hydrothermal liquefaction (CHG) was used to mitigate the high COD level, and recovery the energy from the organics in forms of biogas. Another approach was to directly treat the biomass with CHG, harvesting the energy in the biomass as biogas. The energy balance of these two processes were investigated and evaluated in this study to determine which process could result in more energy in the product. The results suggested that biomass HTL-PHWW CHG gave the highest net energy recovery from the biomass, at 74% efficiency, with heat exchange to recover the energy used for heating the feedstock, which was high in water content. In direct biomass CHG, higher gasification efficiency at higher temperature (500 degree C) did not lead to higher net energy recovery as 38% of the biogas was carbon dioxide, which contributed no energy. The highest net recovery for direct biomass CHG was at 400 degree C, about 51% net energy was recovered from biomass. Third, pyridine and acetic acid were chosen as model compounds for catalytic hydrothermal gasification to study the nitrogen recovery and gasification efficiency from the organic compounds in the post-hydrothermal liquefaction wastewater, due to the relatively high concentration. The results suggested that acetic acid could be used as hydrogen source to facilitate the decomposition of pyridine, achieving an efficiency up to 90% without addition of hydrogen gas at all.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste