Hydrothermal carbonisation of poultry litter: Effects of initial pH on yields and chemical properties of hydrochars

- Hydrothermal treatment of PL was performed at varying pH.
- pH value was varied using CH3COOH or H2SO4.
- Influences of pH on carbonisation were evaluated.
- Structures and chemical compositions of hydrochars were evaluated.

In this study, hydrothermal carbonisation (HTC) of poultry litter (PL) was carried out to evaluate the impact of initial pH using acetic acid (CH3COOH) or sulfuric acid (H2SO4) on the yields and properties of hydrochar (HC). The PL samples were treated by HTC at various initial pH and at 250 °C for 2 h. The HCs produced were characterized by ultimate, proximate and fibre analyses as well as heating value and surface area measurements. The results indicated that undertaking HTC in the presence of acids (CH3COOH, H2SO4) significantly affects the yields and properties of HC. The C content and HHV of the HC increased with decreasing initial pH. In the presence of H2SO4, the hydrochar yield (HY) increased while the ash content was significantly reduced. The lowest ash content and the highest HY were measured in the HC produced from the suspension with an initial pH of 2 using H2SO4.