Effect of microstructure and lignocellulosic components of biochar on NIR absorption

Abstract

Large quantities of agricultural waste and plant by-products are typically discarded or inefficiently utilized as energy sources. This practice poses a significant environmental threat and counters the growing need for sustainable development in modern societies. The comprehensive utilization of biomass-derived carbon materials not only opens up a high-value-added way of utilizing biomass resources but also provides a new perspective to better understand the relationship between nature and sustainable human lifestyles. These carbonized materials have the advantages of a wide-spectrum light absorption spectrum, low cost, simple preparation, and environmental sustainability, and retain their natural form due to their unique structure. It has good prospects in the photothermal field. However, the relationship between the types and properties of biomass and biochar performance, especially NIR absorption, is poorly understood.
This study investigated the link between biomass species and lignocellulosic composition and biochar performance under different pyrolysis conditions for nine biomass species and how they collectively affect the biochar NIR absorption. Nine kinds of biomass samples, i.e., agricultural wastes (walnut shell, peanut shell, rice husk, soybean straw, corn straw, and corncob) and industrial wastes (poplar wood, pine wood, and pine bark) were chosen to pyrolyze and compared lignocellulosic compositions.
36 biochar samples were prepared using a pyrolysis furnace, varying in type and pyrolysis conditions (650 °C, 750 °C, and 850 °C for 0.5 and 1 hour). TGA and elemental analysis were used to study the basic properties of biomass. XRD was used to understand the degree of crystallinity of biochar. FTIR characterization was carried out to analyze biochar surface functional group structure. XPS was used to probe the elemental distribution on the surface of biochar. Finally, the absorbance of biochar was tested by UV-Vis-NIR, and an absorbance test in 808 nm was carried out.
Results showed that shell and bark biomass had more lignin. In addition, the NIR absorption properties of shell and bark biochar (with high lignin content) were generally higher than those of straw and wood. Therefore, it is possible to predict aspects of biochar NIR absorption performance from sample testing of biomass lignocellulose composition and species. This study provides basic research for using lignocellulose composition and biomass species as key indicators for selecting photothermal converters.

Date of Award	17 Mar 2025
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Cheng Heng Pang (Supervisor), Siew Shee Lim (Supervisor) & Edward Lester (Supervisor)