Comparative Assessment of Biochar Stability Using Multiple Indicators

Keiji Jindo,Tomonori Sonoki

doi:10.3390/agronomy9050254

Abstract

Biochar application is one strategy proposed to improve carbon sequestration in soil. Maintaining high carbon content in soil for a long period requires stable biochar. In this work, we assessed biochar stability by two methodologies, i.e., laboratory incubation and chemical oxidation. Biochar was produced at four different temperatures (400 °C, 500 °C, 600 °C, and 800 °C) from rice (Oryza sativa L.) straw and husk, applewood branch (Malus pumila), and oak (Quercus serrata Murray) residues. Results showed that the high-temperature biochars were more stable in both abiotic and biotic incubations, whereas the low-temperature biochars had reduced longevity. In addition, we showed biochars originated from woody material have higher stable carbon than those produced from rice residues. Finally, the oxidative assessment method provided a more reliable estimation of stability than the biotic incubation method and showed a strong correlation with other stability indicators.

Highlights

Carbon sequestration in soil is one of the strategies used to mitigate climate change associated with greenhouse gas emissions
Volatile content decreased and ash content increased with increasing pyrolysis temperature
High-ash biochars enriched with alkaline elements can be a potentially applicable material for plant growth [2,16]

Summary

Introduction

Carbon sequestration in soil is one of the strategies used to mitigate climate change associated with greenhouse gas emissions. The Intergovemental Panel on Climate Change (IPCC) produced a special report on global warming of 1.5 ◦ C (http://www.ipcc.ch/report/sr15/) and proposed the application of biochar to soil as a promising negative emission technology [1]. To extensively and successfully implement this technology, the properties of biochar must first be more fully understood. The interdependency between the types of feedstock and the pyrolysis processes determine biochar properties, and this, in turn, impacts the stability of biochar in soil. Biochar degradation is of interest with regard to soil carbon sequestration and because of the potential for application as a bulk agent to enhance the composting process. Three categories that define biochar stability include (1) carbon structure;

Methods

Results

Conclusion