Impact of Pyrolysis Temperature on the Properties of Eucalyptus Wood-Derived Biochar.

Bruno Caio Chaves Fernandes,Daniel Valadão Silva,Vinícius Patrício Da Silva Caldeira,Tatiane Severo Silva,Matheus De Freitas Souza,Kassio Ferreira Mendes,Taliane Maria Da Silva Teófilo,Vander Mendonça,Ananias Francisco Dias Júnior

doi:10.3390/ma13245841

Abstract

Pyrolysis conditions directly influence biochar properties and, consequently, influence the potential use of biochar. In this study, we evaluated the effects of different pyrolysis temperatures (450, 550, 650, 750, 850, and 950 °C) on the hydrogen potential, electrical conductivity, ash content, yield, volatile matter content, elemental analysis, Fourier-transform infrared spectroscopy results, X-ray diffraction results, scanning electron microscopy results, specific surface area, and micropore volume of eucalyptus wood-derived biochar. The degree of linear association between pyrolysis temperatures and biochar properties was examined using the Pearson correlation coefficient. The results showed a positive correlation of the pyrolysis temperature with the hydrogen potential value, electrical conductivity, and elemental carbon. There was a negative correlation of the pyrolysis temperature with the yield, volatile matter content, elemental oxygen, elemental hydrogen, surface area, aromaticity, hydrophilicity, and polarity indexes. The Fourier-transform infrared spectroscopy data indicated an increase in aromaticity and a decrease in the polarity of high-temperature biochar. The increased pyrolysis temperature caused the loss of cellulose and crystalline mineral components, as indicated by X-ray diffraction analysis and scanning electron microscopy images. These results indicated that changing the pyrolysis temperature enables the production of biochar from the same raw material with a wide range of physicochemical properties, which allows its use in various types of agricultural and environmental activities.

Highlights

Biochar is a carbon-rich porous material produced by biomass pyrolysis under an environment with limited oxygen or anoxic conditions [1,2]
The main transformation observed over this temperature range was the thermal decomposition of lignocellulosic materials and the release of water vapor and Volatile Matter (VM) compounds such as CO, CO2, H2, and CH4, resulting in a high yield loss at lower temperatures [24,25]
Other studies have shown a similar correlation for other materials reacted at different pyrolysis temperatures; that is, other materials show a rapid initial decline in yield at lower temperatures, followed by a smaller and constant reduction at higher temperatures [26,27,28,29]

Summary

Introduction

Biochar is a carbon-rich porous material produced by biomass pyrolysis under an environment with limited oxygen or anoxic conditions [1,2]. Large amounts of agricultural waste are generated worldwide and are not always properly discarded or recycled. Wood production in Brazil annually generates approximately 50.8 million m3 of lignocellulosic waste [6]; eucalyptus is the most cultivated forest species with 7.83 million hectares of planted trees [7] and contributes largely to the creation of this lignocellulosic waste. Waste conversion into biochar by pyrolysis can reduce lignocellulosic waste volume and contribute to power generation, improvements in crop nutrient efficiency, elimination of pathogens, and generation of products with high agronomic and environmental value [8]

Objectives

Methods

Results

Conclusion