A sustainable bioenergy conversion strategy for textile waste with self-catalysts using mini-pyrolysis plant

Abstract

Based on the current economic and environmental analysis of the textile waste streams, textile waste alone can be a promising source of renewable energy. To realize that, catalyst-supported pyrolysis was used in the present research to treat textile waste and convert it into value-added energy carriers while attempting to minimize consumption of consumable chemicals (catalysts) and pyrolysis time and maximize the yield of valuable bio-oil and gases (Methane and Hydrogen). Pyrolysis was conducted on waste jeans (a major fraction of textile waste, rich in cellulose/cotton) with different dye colors (black and blue) and dye-originating heavy metals (used as a self-catalysts). Waste jeans of both colors were pyrolyzed in original condition and after acid leaching to remove the heavy metals for comparison. Also, the pyrolysis experiments were performed according to Technology Readiness Levels (TRL) concept, particularly in laboratory and pilot scale phases. At the first phase, Differential thermal analysis/Thermogravimetric analysis/3D-Fourier-Transform Infrared spectroscopy was employed to simulate the pyrolysis on a lab scale (fundamental level of TRL) and study the thermal and chemical decomposition of the selected samples up to 800 °C. At the second stage, a pilot pyrolysis plant was built (based on the fundamental results received from lab scale) to simulate the industrial energy conversion conditions and obtain the data needed to apply the developed approach at industrial scale. The developed plant consisted of four units: pyrolysis reactor (capacity 300 g, Nitrogen ambient, and max. temp. 800 °C), gas purification unit, instantaneous gas composition analysis unit (to study the effect of pyrolysis temperature on the generated Oxygen, Nitrogen, Carbon Monoxide, Carbon dioxide, Methane, and Hydrogen gases), and gas products collection unit. The pyrolysis products were analyzed using Gas Chromatography–Mass Spectrometry, Fourier-Transform Infrared Spectroscopy, elemental analysis, and Scanning Electron Microscope- Energy-dispersive X-ray Spectroscopy. The results showed that the developed technology successfully converted more than 82% of the feedstock into liquid-gas products and that the untreated feedstock had effective bio-oil yield 36–37.6% (depending on the composition of self-catalysts), which was ∼20% higher compared to the treated batches; 18% reduction in pyrolysis time of untreated feedstock was achieved as well.