Production of biochar for potential catalytic and energy applications via microwave vacuum pyrolysis conversion of cassava stem

Cassava stem waste is abundantly available after starch extraction, hence posing disposal problem and potential risk to environmental pollution. Alternative ways are needed to dispose the waste instead of landfilling and open burning. Microwave vacuum pyrolysis was examined as an alternative method to convert the cassava stem waste into biochar. The cassava stem was first characterized by several analyses followed by conversion into biochar using microwave vacuum pyrolysis over different microwave power. The cassava stem contained high contents of carbon (49.5 wt%) and considerable amount of fixed carbon (27 wt%), indicating its suitability to be used as pyrolysis feedstock. The biochar yield from microwave power of 550 W, 650 W and 750 W were 77%, 73% and 70% respectively. The surface morphology of biochar shows that it consists abundant pores on the surface, suggesting its suitability to be used as catalyst support for energy application, and also as adsorbent for use in adsorption-related process such as dye and heavy metal removal in wastewater treatment or nutrient retention in crops cultivation. The calorific value of the biochar ranged from 19.24 to 20.55 MJ kg−1, showing high energy content for potential use as solid fuel. Our results show that cassava stem can be transformed into biochar for useful energy applications rather than burned as low-grade fuel in boiler or disposed by landfilling.