1. Assessment of Soil Amendment and Carbon Sequestration
Potential of Arundo, Miscanthus and Switchgrass Biochars
Oluwatosin Oginni and Kaushlendra Singh
School of Natural Resources, West Virginia University, Morgantown WV 26505
(Contact:
INTRODUCTION
RESULTS
RESULTS
Biochar’s use as soil amendment and carbon sequestration tool is majorly predicated on its recalcitrance and stability in soil.
Biochar stability determines how long the biochar carbon will remain in the soil particularly as a long term climate change mitigation strategy.
However, biochar aging and soil microbial activities leading to biochar degradation greatly reduced biochar stability hence adversely affecting its performance over time.
Fundamental investigation of biochar recalcitrance and stability is therefore paramount to ensure optimum result from its use for carbon sequestering and soil amending.
Hence, the objective of this work is to assess the carbon sequestration and soil amendment potential of biochars obtained from pyrolysis of arundo, miscanthus and switchgrass harvested from a reclaimed mined land in West Virginia.
Table 1. Biochar’s Properties; An Indicator of Carbon Sequestration and Soil Amendment Potential
Carbon Oxygen Potassium %
Properties
Arundo
Switchgrass
Miscanthus pH
Volatile (%)
Fixed Carbon
Atomic C/N
111.72
145.64
85.64
Atomic O/C
0.15
0.17
Atomic H/C
0.4
0.41
0.45
Porosity
0.83
0.85
Fig 2: Van Krevelen diagram of H/C and O/C atomic
ratios for Biomass, Bio-oil and Biochar
Fig 3: XPS Surface Composition of Arundo Biochar
DISCUSSION
Carbon Oxygen %
Carbon Oxygen Silicon Calcium %
The Van Krevelen diagram shows the atomic ratio of carbon, hydrogen and oxygen. The relatively low H/C and O/C ratio of the biochars depicts a high concentration of carbon. This makes it a good candidate for carbon sequestration.
The XPS surface composition of the biochars showed a graphitic carbon. This shows the recalcitrance nature of biochar to both abiotic and biotic degradation during use in the soil.
The pH values of the biochar are slightly above neutral, which makes it a good candidate for soil amendment. This can be used to improve acidic soil and also enhance microbial activities.
The volatile content and fixed carbon are proportional to each other and they are good indicator of carbon sequestration potential of biochar. Lower volatile content and higher fixed carbon is an indicator that the biochar has less labile/easily degradable carbon.
Dedicated Energy Crop
Pyrolysis
METHODOLOGY
Biochar samples (Arundo, Switchgrass and Miscanthus) were produced via pyrolysis of the biomass samples at temperature of 500 0C for 30 minutes under constant flow of nitrogen.
Ultimate and proximate analyses of the biochar samples were carried out using a CHNS/O and proximate analyzers (Fig 1a &b).
Solid morphology characterization of the biochar samples were performed using a scanning electron microscope (Model: Hitachi-S4700F Scanning Electron Microscope).
The characterization of the surface chemical state and elemental composition of the samples was carried out using X-ray photoelectron spectroscopy (Model: PHI 5000 VersaProbe XPS/UPS) with a spectral range of 0 to 1400 eV binding energy and energy resolution of 0.50 eV.
Fig 4: XPS Surface Composition of Switchgrass Biochar
Fig 5: XPS Surface Composition of Miscanthus Biochar
CONCLUSION
The properties of the biochars characterized in this work shows that the three biochars are a good candidate for soil amendment and carbon sequestration.
Also, the properties further gives an indication of the alternative use of the biochar for bioadsorbent production.
ACKNOWLEDGMENT
This research was supported by funds provided by the United States Department of Agriculture McStennis Grant (Project# WVA00097).
Fig 1b: Thermogravimetric Analyzer
Fig 1a: CHNS/O Analyzer
Fig 6: SEM Micrograph of Miscanthus Biochar
Fig 7: SEM Micrograph of Switchgrass Biochar