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The harmless disposal and resource utilization of human feces is important to the sanitation process. Hydrothermal liquefaction (HTL) can convert toilet feces into bio-crude oil and reduce waste. In this study, an integrated eco-toilet system was developed by combining vacuum micro-flush toilets with a continuous hydrothermal liquefaction reactor. The system operated stably for over 10 h. This system can serve 300 households and save 2759 m3 of water per year compared to traditional flush toilets. The energy recovery from the feces was 2.87 times the energy consumed for the HTL process. The HTL bio-crude oil yield was 28 wt%, and the higher heat value (HHV) of the bio-crude was 36.1 MJ/kg. The biochemical compounds of the bio-crude oil consisted of acid ester, hydrocarbons, phenols, and a nitrogenous heterocyclic compound. The carbon in the human feces was mainly transferred to the bio-crude oil, while nitrogen was mainly transferred to the aqueous phase product. The post-HTL aqueous stream could be treated and used as fertilizer. This system achieves energy self-sufficiency, along with water and energy savings. This integrated eco-toilet effectively converts feces into bio-crude to realize waste reduction and resource utilization of human feces.

Sustainable livestock production plays an important role in meeting the growing global demand for animal products. Livestock manure and odor emission are regarded as the major obstacles to the low-carbon livestock farming. In response, we propose a novel loop for the valorization of livestock wastes, via bridging manure and the typical odor NH 3 with P-doped hydrochar. P-doped cow manure hydrochar was facilely prepared via hydrothermal carbonization followed by H 3 PO 4 activation. The organic composition and crystallinity of hydrochar as the precursor, depending on hydrothermal severity, significantly impacted the subsequent H 3 PO 4 activation behavior. The activated sample with modified surface exhibited favorable NH 3 adsorption capacity in the dynamic adsorption experiment. Density functional theory calculation confirmed that the P-containing group improved the NH 3 adsorption efficiency as the active site. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses demonstrated the oxidation of reduced phosphorus groups during NH 3 adsorption in room temperature. Phosphorus species strengthened the immobilization of NH 3 on the surface via Brønsted and Lewis-type acid−base interaction. This study provided a new strategy to develop a green NH 3 adsorbent from the manure-based hydrochar, supporting the further investigation on the promising solution of odor control and waste valorization in livestock farms.

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