Motivation

Our project is a direct response to an ongoing problem in our community—a lack of green and clean technologies for efficient textile waste management.^1-4 To address this issue, we sought to develop a novel method of upcycling and repurposing textile waste into a value-added product. During the initial stages of our project, we consulted local experts in renewable textiles and sustainable practices and discovered that blended textiles are the most problematic to recycle. Subsequently, our literature search revealed that blended textiles are commonly composed of cellulose, microplastics, and keratin.⁵ This uncovered numerous possibilities for the development of innovative recycling methods. In the following weeks, ReneWool was born!

ReneWool is a method of upcycling the blended textile waste currently filling landfills into a value-added commodity—spider silk! In addition to providing an alternative to unsustainable waste disposal methods,⁶ ReneWool raises awareness about the environmental impacts of global textile waste and upholds the UN Sustainable Development Goals 12 and 13.⁷

The Necessity for ReneWool

Global Issues

In 2022, the United Nations identified the fashion industry as the second-largest contributor to environmental pollution after the oil industry, responsible for 8% of global carbon emissions and 20% of all wastewater production.⁸ Businesses exploit the market by producing and selling large quantities of cheap clothing, driving an unprecedented increase in global textile demand.^{9, 10} This global phenomenon is known as fast fashion.

The fast fashion industry accelerates textile production, amplifying the environmental damage caused by carbon emissions and chemical waste. Wastewater from fabric treatment processes contains heavy metals and toxins, which contaminate ecosystems and pose significant health risks as they biomagnify up food chains.^{11, 12}

Without effective fabric waste management strategies, the problem will worsen. In fact, from 2007 to 2014, textile fiber production grew at an annual compounded rate of 3.7%, demonstrating the need for urgent action.¹³

Local Issues

Textile waste is a significant problem in Edmonton. In the early stages of ReneWool’s development, we discovered the inadequate allocation of our city’s resources towards effective textile waste management solutions. The 2015 Waste Services Expenditures report indicated that in 2018, only 5% of the City of Edmonton’s funding was directed toward waste prevention and reuse, while 35% was allocated to landfill operations.¹ This policy decision has further compounded the problem by neglecting to invest in research and development of innovative recycling and reuse methods. Researchers from the University of Alberta and Simon Fraser University have highlighted that no company within Edmonton currently possesses the capacity to recycle clothing.² As a result, non-profit organizations and small businesses, with limited financial support from the city, bear the burden of managing textile waste.³

Our city also lacks a municipal textile recycling program and public education on the issue. In 2016, the city launched the WasteWise app to raise awareness about local waste management. However, the app advises users to dispose of worn clothing in the garbage bin, contributing to the rising volume of waste sent to landfills and exacerbating the environmental issues associated with textile waste.^{3, 4}

Based on 2018 data on Canadian waste generation, an estimated 462,704 tonnes of textile waste was produced nationwide, of which 65% could have been reused and 21% recycled.¹⁵ These nationwide statistics are indicative of the combined waste of each municipality, and it's up to each local government to make a change. This highlights the critical need to revise Edmonton’s approach toward implementing alternative waste management strategies.

Current Strategies to Process Textile Waste

There are three methods of processing textile waste—mechanical, chemical, and biological.

1. Mechanical

Mechanical techniques involve melting synthetic fibers for upcycling or physically tearing fabrics to retrieve pure textile material.¹⁶ Despite their scalability and cost-effectiveness, mechanical processes yield low-value materials, a considerable obstacle to the reutilization of textile waste.¹⁷

2. Chemical

Chemical methods possess the theoretical capacity to depolymerize all types of polymers; however, practical applications of these processes have yet to be developed or standardized.¹⁶ Consistent with the nature of chemical reactions, the chemical recycling process for textile waste is contingent upon the input of pure materials.^{16, 18} Therefore, recycling blended fabric waste via chemical methods inadvertently necessitates additional purification and separation steps, increasing economic and environmental costs.^{16, 18} Moreover, chemical waste byproducts can be toxic, and these processes require large quantities of water and energy.¹⁸

3. Biological

The innate limitations of mechanical and chemical textile recycling has led to increased interest in biological methods. In the context of achieving circularity and minimizing environmental impacts, biological recycling offers the following advantages over mechanical and chemical methods. Enzymes can overcome the problems related to blended fabrics—enzymes are specific to their substrate types, enabling efficient breakdown of blended fabric waste.^{6, 18} Additionally, bio-based processes tend to require very low energy demand, mild reaction conditions, and use relatively fewer harmful solvents and chemicals, reducing dependence on the fossil carbon sources typically involved in thermal processing.⁶

Our Solution

The innate limitations of mechanical and chemical textile recycling has led to increased interest in biological methods. In the context of achieving circularity and minimizing environmental impacts, biological recycling offers the following advantages over mechanical and chemical methods.

1. Degradation Process

Cellulose and polyesters are exceedingly common in textile blends, while keratin makes up a significant portion of the fibers we derive from animals.^{5, 17} Considering the challenges facing enzymatic degradation of polyesters—enzymes are unable to penetrate the material, limiting degradation to the surface^{18, 19}—we chose to target keratin and cellulose in our degradation system.

The first step in the ReneWool system is the degradation of blended textile waste. To achieve this, we searched the literature for enzymes degrading keratin and cellulose. We selected the keratinase KerDZ due to its relatively high thermostability and ability to function at a wide range of pHs, as well as its ability to degrade wool when expressed in E. coli.^{20, 21} The cellulase Cel-CD was selected based on its ability to be secreted by E. coli, as well as its catalytic abilities.²² These two enzymes are capable of converting keratin and cellulose into amino acids and sugars respectively, allowing us to convert waste material into a green nitrogen and carbon source for spider silk synthesis.

2. Spider Silk Production

We chose spider silk as our end-product due to its incredible physical properties and its wide array of applications, which include tissue scaffolding, controlled drug release, and even STEM cell culturing.^23-25 Our spider silk gene, (A3I)3-A14, is a derivative of the recombinant protein NT2RecCT and has toughness equal to native dragline spider silk.^{26, 27} In addition to its desirable physical properties, this protein is produced in large quantities by E. coli in bioreactors, allowing feasible scale-up of our system.²⁶

Advantages of Our System

While our prototype is limited to keratin and cellulose degradation, alternative enzymes can be added to expand the system to target other components of mixed textile blends, allowing for the development of a robust textile waste management system. The adoption of ReneWool not only supports eco-friendly practices but also has significant economic potential. The use of waste to create a value-added commodity with a wide array of applications provides a commercial, as well as environmental, incentive for the development of this system. Additionally, the use of mild reaction conditions requiring less energy input when compared to other methods of textile recycling provides a compelling case for industrial implementation.⁶