Abstract:

Objective In alignment with the implementation of the national dual-carbon policy, the silk industry, as one of the distinctive sectors within our country, has an urgent need for the quantification of the carbon footprint associated with silk textiles. This imperative undertaking aims to formulate production processes that are inherently more eco-friendly and carbon-efficient. Within the multifaceted realm of silk manufacturing, the refining phase holds particular significance, thereby rendering an investigation into its carbon footprint, an indispensably requisite endeavor.

Method A methodology was devised for the dissection of electricity consumption within various stages and processing techniques of the refining process. Furthermore, a computational framework was introduced to account for carbon emissions arising from the transportation of raw materials and auxiliary substances, alongside direct greenhouse gas emissions resultant from wastewater treatment. By harnessing primary activity data garnered from on-site investigations, a comprehensive assessment of the carbon footprint(CFP) pertaining to the refining phase has been conducted.

Results The study established systematic boundaries for two distinct refining processes and the methodologies and equations employed for carbon footprint calculation were elucidated, accompanied by an enumeration of greenhouse gas emission factors pertinent to various materials or energy sources utilized during the calculation process. The distribution of carbon footprints was expounded from the vantage points of diverse inputs and processing stages. The outcome of the calculations reveals that for non-elastic fabrics, the carbon footprints for the rectangular tank refining and star-shaped frame refining processes were 35.06 and 37.47 kg CO₂e/(100 m), respectively. Concerning elastic fabrics, the carbon footprints for the two processing techniques were 57.60 kg CO₂e/(100 m) and 59.99 kg CO₂e/(100 m), respectively. From an input-output perspective, with respect to non-elastic fabrics, the predominant sources of emissions in descending order were steam 47.88%), direct methane emissions (35.52%), and chemical usage (10.59%). For elastic fabrics, the major emission sources in descending order are natural gas (34.63%), steam (29.52%), direct methane emissions (21.91%), and chemicals (6.53%). Analyzing the processes, for non-elastic fabrics, the refining process (56.08%) and wastewater treatment (37.63%) constitute the most substantial contributors to carbon emissions. For elastic fabrics, the shaping and finishing process (38.33%), refining process (34.57%), and wastewater treat-ment (23.21%) were found to be the most carbon-intensive stages. Sensitivity analysis indicated that within a 95% confidence interval, variations in methane correction factors result in fluctuations of ±9.93% (non-elastic fabric degummed using rectangular tank),±8.13% (non-elastic fabric degummed using star-shaped frame),±6.04% (elastic fabric degummed using rectangular tank), and ±5.08% (elastic fabric using star-shaped frame) with regard to total carbon emissions.

Conclusion The findings of this study demonstrate that the CFP of the star-shaped frame refining process is slightly larger than that of the rectangular tank refining process. Moreover, the shaping and finishing process of elastic fabrics exhibits a substantial consumption of natural gas, leading to a significantly higher CFP when compared to non-elastic fabrics. Within the refining phase, the primary sources of carbon emissions are steam, natural gas, and direct methane emissions resulting from wastewater treatment. Mitigation of carbon emissions can be effectively achieved through measures such as increasing the reuse frequency of refining hot water, enhancing the processing efficiency of shaping and finishing, recovering and utilizing methane generated in wastewater treatment, and adopting non-overloaded oxygen-consuming modes.

Key words: refining, silk fabric, carbon footprint, wastewater treatment, life cycle assessment