Comprehensive insights into the impact of straw types, temperature and atmosphere on pyrochar properties and its enhancement potential for anaerobic digestion

Abstract

Pyrochar has been extensively utilized; however, there is a dearth of research on the impact of pyrochar characteristics on the biogas production potential of anaerobic digestion (AD). To address this knowledge gap, in this study, 27 types of pyrochar were prepared through the pyrolysis of various agricultural straws (corn stover, cotton stalks, and rice straw) under different temperatures and atmospheres. Subsequently, the properties of these pyrochars and their potential to enhance AD were systematically investigated. The results revealed that these pyrochars mainly contained –OH groups, followed by aromatic rings. In particular, the corn stover-600-CO₂ pyrochar had the highest specific surface area of 131 m² g⁻¹ and a pore volume of 0.147 cm³. Moreover, this pyrochar had an excellent electrical conductivity, with a low resistivity of 781 Ω cm, which was beneficial for electron transfer during AD. When the corn stover-450-N₂ pyrochar was used to enhance AD, the highest CH₄ production rate and CH₄ content in biogas reached 69.5 mL g⁻¹ VS/d and 67.1%, respectively. Correspondingly, the highest cumulative CH₄ production reached 584 mL g⁻¹ VS, which was 1.8 times higher than that of the control group. This study can offer a crucial foundation for the application of suitable pyrochar in AD.