Microwave-assisted pyrolysis of food waste: optimization of fixed carbon content using response surface methodology

Abstract

Pyrolysis of food waste using microwave irradiation was carried out in this study to produce quality biochar for heating applications. Optimum conditions for microwave-assisted pyrolysis of food waste particles were determined using response surface methodology (RSM). Combined effects of the operating variables, namely pyrolysis temperature (°C), residence time (min) and nitrogen flow rate (mL min⁻¹), were analyzed by conducting 20 experiments. Microwave-assisted pyrolysis results were correlated by applying RSM with the regressions coefficients of 92.90% for biochar and 90.305% for fixed carbon content. Microwave power of 450 W yielded 60.03 wt. % of biochar with a fixed carbon content of 48.71 wt. % under the optimum pyrolysis conditions of 400 °C temperature, 30 min residence time and 50 mL min⁻¹ of nitrogen flow rate. The higher heating value of the biochar was 33.35 MJ kg⁻¹.

Keywords:

• microwave irradiation
• food waste
• biochar
• fixed carbon
• response surface methodology

Acknowledgements

The first author gratefully acknowledges the National Institute of Technology, Karnataka Surathkal, for the financial support to purchase the microwave reactor under the annual plan fund [No. 233/NITK/CHE/APF/2014-15/A9 dated 23-02-2015].

Disclosure statement

No potential conflict of interest was reported by the authors.