Pyrolysis of dedicated bioenergy crops grown on reclaimed mine land in West Virginia

• Pyrolysis of Miscanthus and Switchgrass clonal varieities in a fixed-bed batch reactor was carried out.
• Bio-oil, biochar and non-condensable gas were produced.
• Miscanthus (Private variety) had the highest bio-oil yield of 50.61%.
• Pyrolysis products properties were not significantly influenced by the feedstock varieties.
• N2, CO and CO2 were the major components of the non-condensable gas.
• Surface chemistry analysis of the biochars showed carbon and oxygen to be the major chemical constituents of the biochars’ surfaces.

Dedicated bioenergy crops grown on marginal lands such as reclaimed mine lands and other non-arable lands are auspicious cellulosic sources for sustainable bioenergy production. In this study, characterization of pyrolysis products were documented for two dedicated bioenergy crops grown on reclaimed coal-mine lands in West Virginia. Two clonal varieties (Private and Public varieties) of Miscanthus (Miscanthus x giganteus) and two varieties (Bomaster and Kanlow varieties) of Switchgrass (Panicum virgatum L) were used in this study. The oven-dried samples were pyrolyzed in a fixed-bed batch reactor under an inert condition and at a temperature of 500 °C to produce biochar and bio-oil (vapor condensate). The pyrolysis product, energy and carbon conversion yields were calculated. Additionally, biochar and bio-oil were characterized for elemental composition, volatile, ash and calorific values. Results showed that there was no significant difference in the biochar yields (about 30.00% yield) obtained from the clonal varieties of Switchgrass and Miscanthus. The bio-oil yields were in the range of 45.00–51.00% with the Miscanthus (Private variety) having the highest bio-oil yield of 50.61%. The carbon content of the biomass, biochar and bio-oil were found to be 46.80–48.02%, 77.72–80.23% and 54.68–59.68%, respectively. Average calorific values were found to be 19.49 MJ/kg, 29.01 MJ/kg and 24.98 MJ/kg for the biomass, biochar and bio-oil, respectively. Results for the surface chemistry of the biochars showed carbon and oxygen to be the major chemical constituents of the surfaces of the biochars. Carbon dioxide (CO2), nitrogen (N2) and carbon monoxide (CO) were found to be the major components of the non-condensable gas and the CO:CO2 ratio showed that the non-condensable gas cannot be used as a fluidizing medium.