DISCUSSION

Fig 6: SEM Micrograph of Switchgrass Biochar

Fig 7 SEM Micrograph 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.

Biochar is a stable recalcitrant carbonaceous material produced from biomass pyrolysis alongside bio-oil and non-condensable gas.

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.

This assessment is relevant in improving current estimates of the residency time for biochar, its suitability as a vehicle for carbon sequestration and production of value-added products.

INTRODUCTION

Assessment of Soil Amendment and Carbon Sequestration Potential of Miscanthus and Switchgrass

Biochar

Oluwatosin Oginni and Kaushlendra SinghSchool of Natural Resources, West Virginia University, Morgantown WV, USA

RESULTS

Volatile matter

Solid morphology

pH

Fig 1: Van Krevelen Diagram of H/C and O/C atomic ratios for Biomass, Bio-oil and Biochar

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

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 3: XPS Surface Composition of Switchgrass Biochar

Carbon Oxygen 86.78 13.22 %

Fig 4: XPS Surface Composition of Miscanthus Biochar

Carbon Oxygen Silicon Calcium 85.25 13.18 0.88 0.69 %

Fig 5: SEM Micrograph of Arundo Biochar

Fig 2: XPS Surface Composition of Arundo Biochar

Carbon Oxygen Potassium 80.50 15.33 4.17 %

METHODOLOGY

Fig 1b: Thermogravimetric Analyzer

Figure 1c: MultiPcynometerFig 1a: CHNS/O Analyzer

Properties Arundo Switchgrass Miscanthus

pH 7.85 + 0.10 7.57 + 0.18 8.44 + 0.16

Volatile (%) 14.87 + 0.40 16.82 + 0.64 16.69 + 1.62

Fixed Carbon 74.62+0.52 76.78 + 0.10 74.59 + 2.77

Atomic C/N 111.72 145.64 85.64

Atomic O/C 0.15 0.15 0.17

Atomic H/C 0.4 0.41 0.45

Porosity 0.83 0.83 0.85

Table 1. Biochar’s Properties; An Indicator of Carbon Sequestration and Soil Amendment Potential

Fig 1d: pH Meter