Textile and Food Waste Biorefineries towards Green and Sustainable Circular Economy


Student thesis: Doctoral Thesis

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Award date9 Aug 2019


Circular economy is a process in which the value of product, resource and material can be maintained in the economy instead of the old linear system “take, make, use and discard”. It can contribute to the utilization of renewable resource, reduction of pollutant generation, and the development of bio-benign products. Biorefinery is considered as one of the green and sustainable strategies towards circular economy, since waste can be converted as value-added products. Three research projects were reported in this thesis with the aim of development of circular waste-based biorefinery via valorization of textile and food waste as examples.

The first part of this thesis focused on the recovery of glucose and polyester from textile waste by enzymatic hydrolysis. In this work, we investigated the optimal conditions for enzymatic hydrolysis and recycling of textile waste with the lowest energy and enzyme inputs. The key factors related to hydrolysis were investigated in this study, such as substrate loading, temperature and pH. Regarding enzyme inputs, the dosages of cellulase and β-glucosidase were also investigated. The optimum enzymatic hydrolysis condition was using 20 FPU/g cellulase and 10 U/g β-glucosidase at 50 °C and pH 5, based on the criterion for minimizing enzyme dosage and maximizing glucose recovery. The maximum glucose recovery yield of 98.3% was achieved after 96 h hydrolysis.

The second project proposed to evaluate the feasibility of valorization of glucose-rich hydrolysate from textile waste into succinic acid by incorporating biochar treatment. Biochar was applied to remove colorants from a textile waste hydrolysate. After optimization of nitrogen types and dosages in shake flasks, the highest succinic acid titer and yield were obtained at 19.6 g/L and 0.76 g/g, respectively, when supplemented with 30 g/L tryptone as the nitrogen source. The in situ fibrous bed bioreactor (isFBB) can further improve succinic acid production, up to 28.8 g/L with a yield of 0.61 g/g without pH control.

In the third project, we investigated the possibility of enhancing the enzymatic hydrolysis of food waste using ultrasonic technology. Ultrasonic pre-treatment could reduce the particle size of the blended food waste significantly, resulting in a better interaction with the enzyme. As a consequence, the glucose yield of enzymatic hydrolysis was ∼10% higher for food waste pre-sonicated under optimal conditions than for the untreated control. In addition, the time required to achieve high yields of glucose could be more than halved using ultrasonic pre-treatment. This could enable the hydrolysis reactor size or the enzyme usage to be reduced by more than 50%.

The three projects presented the valorization of textile and food waste in novel biorefinery strategy, integrated with physical, chemical and biological methods. These examples successfully developed waste-based biorefinery to capture the inherent nutrients for production of value-added products. It was demonstrated that waste biorefinery could contribute to the development of green and sustainable circular economy.