Pyrolysis of orange peel waste to pyrofuels and pyrochar: optimization and techno-economic insights for industrial scale-up

Abstract

Biomass presents a sustainable alternative to fossil fuels; however, it faces limitations such as high moisture content, low bulk density, and poor grindability. This study investigates the pyrolysis of waste orange peels to produce pyro-char, pyro-oil, and pyro-gas, a process that has been rarely reported in the literature. The effects of pyrolysis temperature, feedstock mass, and heating rate on the yield of these pyro-products were systematically investigated. The biomass was characterized using proximate analysis and thermogravimetric analysis (TGA), while the pyro-products were analyzed for their higher heating value (HHV), lower heating value (LHV), morphology and elemental composition via scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and chemical composition using gas chromatography mass spectrometry (GC-MS). Critical parameters influencing the pyrolysis outcomes were identified: feedstock mass (1–3 kg), temperature (573–1173 K), and heating rate (10–30 K min−1). Under optimal conditions of 2 kg feedstock mass, 873 K temperature, and a heating rate of 20 K min−1, the theoretical yields were 26.52 wt% pyro-char, 22.76 wt% pyro-oil, and 50.72 wt% pyro-gas, with an overall process desirability of approximately 0.7. Experimental yields showed slight deviations, resulting in 28.12 wt% pyro-char, 22.89 wt% pyro-oil, and 48.99 wt% pyro-gas, all within a ±5.7% margin of the theoretical values. The estimated payback period for the initial investment is 1.3 years at a 10% discount rate, which is considerably shorter than the previously reported 6-year period for pyro-gas and pyro-oil production. Scale-up to larger plants is expected to further reduce this duration. This study bridges the gap in comprehensive techno-economic analyses of industrial-scale waste orange peel pyrolysis by producing pyro-char, pyro-oil, and pyro-gas, a three-product yield not previously reported. It offers a sustainable approach to valorizing orange peel waste into high-value products, aligning with Industry 5.0 principles and the United Nations 2030 Sustainable Development Goals.