Final Report: Recycling for Value-Added Regenerated Cotton FiberEPA Grant Number: SU836787
Title: Recycling for Value-Added Regenerated Cotton Fiber
Investigators: Liu, Hang
Institution: Washington State University
EPA Project Officer: Page, Angela
Project Period: September 1, 2016 through August 31, 2017
Project Amount: $14,951
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2016) RFA Text | Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Materials & Chemicals , Sustainability
The worldwide fiber consumption for consumer textile products has been growing steadily in the past several decades due to population growth and living standard improvement. Given the fact that only about 15% of the post-consumer textiles are recycled, the amount of textiles that contribute to the municipal solid waste (MSW) increases accordingly. Statistics from the U.S. Environmental Protection Agency (EPA) shows that every American adult on average abandons 31 kilograms (i.e., 68 pounds) of textiles each year, which account for 5% of MSW. As a natural cellulose fiber with appealing comfort and easy care properties, cotton has been utilized in consumer products (e.g., clothing and home textiles like towels and bedding) significantly more than most other fibers. Approximately two-thirds by weight of the textile wastes are cotton products (3.7% of the MSW). The recycling rate of cotton waste is estimated at 5%, lower than the overall textile recycling rate at 15%. This waste is either buried in landfills or burned in incinerators. Substantial amounts of greenhouse gases (methane and carbon dioxide) and toxic chemicals and odors are generated in landfills and/or incinerators. This not only severely harms the environment and human health, but also contradicts the efficient use of natural cellulose resources.
The current dominating cotton recycling method is fiber reclamation, where fibers are extracted from used products to manufacture into yarns or to produce nonwoven fabrics. The quality of reclaimed fibers is lower than virgin cotton fibers and, therefore, they are mostly used for lower grade products such as cleaning wipes, cotton paper, and building insulation material. How to recycle cotton waste to efficiently use this natural resource has become a prominent challenge facing the textile industry and government agencies. This research proposed an innovative solution to this challenge by dissolving cotton waste with environmentally friendly solvents and spinning high quality virgin regenerated fibers for a broad range of end uses. The specific objectives of Phase I research included:
1) Establish a solvent system for dissolving cotton post-consumer waste to obtain cotton solution that can be spun into fibers;
2) Wet spin the cotton waste solution into regenerated fibers and evaluate fiber properties;
3) Assess the cost of the regenerated fiber and the environmental impact of the fiber production process; and
4) Develop educational tools.
The outputs of the Phase I project include the following:
(1) Experimented with several pretreatment methods to increase the solubility of cotton waste;
(2) Invesitgated the efficiency of several solvent systems;
(3) Carried out fiber production through wet spinning;
(4) Measured fiber properties;
(5) Analyzed cost and life cycle assessment (LCA) of the produced fibers compared to virgin cotton and viscose rayon;
(6) Developed educational material.
The results/outcomes are listed below:
(1) Continuous fibers with fabulous luster were successfully produced by the proposed cotton recycling method. The degree of hydrolysis pretreatment, cotton dissolving temperature, mechanical agitation during dissolving, solvent system composition, and coagulation bath composition all affected the process.
(2) Physical/mechanical properties of the regenerated fibers were evaluated. (a) Fiber with diameters at approximately 20 μm were produced with round cross-section and smooth longitudinal surface. The round cross-section shape of regenerated fibers was different from the bean shape of original cottons, which imparted the regenerated fibers very good luster. (b) Fiber tensile properties were measured in accordance to ASTM Standard Test Method D3882/3882M – 14 (Tensile Properties of Single Textile Fibers). The tenacity of white regenerated fibers was about 1.6 g/den and elongation was 11%. The results were for as-spun fibers without additional drawing process, which improves the molecular chain orientation and crystallinity that lead to increased strength. (c) Initial Thermal Gravity Analysis and Fourier Transform Infrared Spectroscopy results indicated the regenerated fibers had same chemical composition as the original cotton. The dissolving process did not alter the cellulose molecular structure.
(3) LCA framework has been developed to compare the three major environmental impact indicators, i.e., the water use [m3], energy consumption [GJ], and global warming potential [kg CO2 equivalent (CO2e)].
(4) Educational materials were developed for increasing the awareness of recycling textile waste through appropriate channels and distributed to the public at various events.
In Phase I, the team has successfully developed a solution system to recycle cotton for regenerated fibers. The fibers exhibited good luster, intrinsic colors, and sufficient tensile strength for a broad range of applications for consumer products. The initial work accomplished demonstrates the great potential for technology commercialization. Once commercialized, this novel cotton waste recycle technique will contribute tremendously to protecting the environment, strengthening our communities, and fostering prosperity by turning waste into value-added fibers via an environmentally friendly production method.