Special Feature

Hong Kong produces a staggering 800,000 tonnes of textile waste every year. Only a small amount of such textile, fashion and consumer waste is recycled. Most has been sent to landfills, creating another environmental headache, noted Dr Carol Lin Sze-ki, Associate Professor in CityU's School of Energy and Environment. “Hong Kong's current landfills will be full in a few years,” she said. “Thus we urgently need a sustainable recycling method for such waste.”

After four years of exploration, Dr Lin and her research team have now come up with a highly promising solution: Hong Kong's first green technology capable of recycling mixed textile waste and turn it into value-added materials such as glucose and synthetic fibres. The innovation won a Gold Medal at the 46th International Exhibition of Inventions of Geneva in 2018.

Novel approach

• Pre-treatment: modifying the structure of textile waste with reusable chemicals to reduce the amount of fibre.
• Enzyme production: cultivation of fungi on the textile waste for hydrolysis.
• Application of enzyme solution and hydrolysis: thoroughly blending the solution with pre-treated textile waste, then undergoing hydrolysis in a bioreactor to obtain soluble glucose.
• Conversion: The decomposed materials can be converted into different products. For example, polyester can be re-spun into polyester fibres for the textile industry while glucose can be converted into various bio-based substances, including bio-plastics and bio-chemicals.

International recognition

The research proved long and hard, and Dr Lin is keen to laud both her team's on-going endeavours and partner support over the years. “I really appreciate their effort and contribution in helping this project succeed,” she said. Dr Lin pays further tribute to CityU for providing her with brilliant and dedicated research students. “Enzymatic hydrolysis and microbial fermentation are taking place every second. To obtain an accurate production and growth chart, this meant three groups of researchers had to work shifts round the clock and perform non-stop observation – a really exhausting process,” Dr Lin noted.

Given the scale and intensity of the research project, few in the city have tackled this area previously, with Dr Lin's biorefinery strategies becoming the first of their kind to be successfully developed in Hong Kong. “In the past, only Europe and the mainland conducted such research,” she explained. “Our technology often received praise from around the world when we shared our research results at international conferences. Now that our efforts have finally paid off, it makes all the hardships involved worthwhile.”

Sustainable recycling economy

Dr Lin herself is deeply committed to teaching and research, sometimes working seven days a week. Driving her on is a passion for her work and the dedication of team members. “It would be impossible to tackle all the tasks myself,” she said. “In addition, the enthusiasm of my researchers gives me the motivation and determination to keep pushing everyone forward.”

With HKRITA securing more funding, the second stage of the study will be launched at the end of March 2019. In this phase, Dr Lin and her team will act as consultants. The aim is to ascertain how this home bred technology can contribute to the creation of a sustainable recycling economy for textile waste disposal around the world.

Dr Lin extracts a hydrolysed textile waste sample.
連博士示範抽取水解紡織廢料的樣本。