A study on the products from co-pyrolysis of fruit waste with high density polyethylene

Valorization of municipal solid waste (MSW) plays a crucial role in the circular economy by transforming waste into valuable materials. Existing disposal methods of fruit waste result in losing valuable bioactive materials such as polyphenols, phytochemicals and antioxidants leading to economic value loss. Pyrolysis is considered a promising thermochemical pathway to produce valuable materials such as bio-oil and char. This study investigates the co-pyrolysis of fruit peel waste (FPW) comprising banana, apple, orange and cucumber peels with commercial high-density polyethylene (HDPE) as surrogates of MSW. This work is focused on interactions between the volatiles evolved from the pyrolysis of biochemical constituents and hydrocarbons and quality of pyrolysis products. Experiments were performed in a tubular reactor to assess the effect of feedstock composition, temperature and CO 2 environment. The HDPE composition in the feedstock varied from 33 to 67% and the pyrolysis temperatures investigated were 500, 600 and 700°C. Finally, an equal composition feed with FPW:HDPE (1:1) was co-pyrolyzed at 600°C in CO 2 environment to understand the effect of pyrolysis environment on the quality of bio-oil and char. The bio-oil obtained from the interaction of the components in the FPW and HDPE was analyzed by gas chromatography-mass spectrometer. This analysis was supplemented by proton nuclear magnetic resonance and Fourier-transform ion cyclotron resonance mass spectroscopy for detailed analysis of heavier compounds present in the bio-oil. Detailed product composition revealed that the formation of hydrocarbons was promoted with increasing HDPE (9-15%), while significant deoxygenation was observed with increased temperature. Wax formation also significantly reduced (50-100%) during co-pyrolysis. Char samples were analyzed using scanning electron microscopy, elemental analysis and Fourier-transform infrared spectroscopy. HDPE loading and the CO 2 environment stabilized the char by promoting deoxygenation.