Hydrothermal treatment enhances energy recovery from pig manure digestate and improves the properties of residues

Abstract

Energy recovery from biowaste is of high significance for a sustainable society. Herein, hydrothermal treatment (HT) was applied to valorize pig manure digestate. The effects of hydrothermal operational parameters, including temperature (130-250 °C), residence time (15-90 min), and total solid (TS) concentration (10%-20%), on reducing sugar yield were investigated in this study. Among them, hydrothermal temperature was identified as the most important factor influencing reducing sugar yield, followed by the TS concentration and time. The optimal hydrothermal conditions for the pig manure digestate were 175.6 °C, 35.4 min and a TS concentration of 10% with a reduced sugar yield of 9.81 mg gTS⁻¹. The addition of hydrolysate could enhance methane production by 21.6-50.4% from the anaerobic digestion of pig manure than that without the hydrolysate addition. After HT, the hygienic quality, including fecal coliform number and ascaris egg mortality, was improved in the residual digestate. Antibiotics such as sulfamonomethoxine, oxytetracycline, doxycycline and sulfaclodazine in the pig manure digestate were decomposed during HT and decreased environmental risk. These findings indicated that the hydrothermal process might be an effective technique to recover energy from the digestate of livestock and poultry manure and to improve the residual digestate for subsequent utilization.

Keywords:

• Pig manure
• hydrothermal treatment
• digestate
• anaerobic digestion
• antibiotics

Disclosure statement

The authors report there are no competing interests to declare. All authors actively participated in processing, writing, editing, and reviewing the manuscript.

Data availability statement

The data that support the findings of this study are available on reasonable request from the corresponding author.

Additional information

Funding

This work was financially supported by Natural Science Foundation of Zhejiang province with Grant No. LZ20E080002, National Natural Science Foundation of China with Grants No. 91851109 and 41911530193, Central Guide Local Science and Technology Development of Xinjiang Uygur Autonomous Region with Grant No. ZYYD2023B16, and project of research and demonstration on thermal hydrolysis treatment of mixed liquor after anaerobic digestion of livestock and poultry manures.