Valorisation of adzuki bean waste to biofuel precursors via pyrolysis: kinetics, product distribution and characterisation

The use of non-food materials such as agro-residues as feedstock for renewable energy production continues to generate greater interests due to the environmental challenges from the utilisation of fossil-based fuels. This study gives the first report on thermochemical characteristics, pyrolysis kinetics and pyrolysis product distribution from adzuki bean waste (pod). The pyrolysis characteristic was evaluated under a non-isothermal condition at a different heating rate (10, 15 and 20 A degrees C/min) and kinetic parameters determined using distributed activation energy model. The result indicates that the model adequately described the pyrolysis characteristics of the feedstock with high correlation coefficient (R (2) > 0.9) and apparent activation of 140.81 kJ/mol. The result of pyrolysis study revealed that adzuki bean pod could be valorised into solid, liquid (bio-oil) and gas products with maximum bio-oil yield of 46.57 wt% at 600 A degrees C. The bio-oil collected contains high-value fuel precursors and value-added chemicals such as phenol and phenol derivatives, benzene and methyl ester. The gas product comprised of combustible gases, which can serve as an alternative energy source to the pyrolysis system. The solid bio-char product is predominately a porous carbon material with indicators of high stability. This material can also be utilised for energy application in addition to carbon sequestration. The presence of macronutrients suggests its suitability for bio-fertiliser application. This study shows that adzuki bean waste is a potential feedstock for production of alternative energy and valuable biomaterials.