Abstract:

Objective In response to our national goal of "achieving a carbon peak by 2030, and carbon neutrality by 2060", the silk industry urgently needs to carry out life cycle assessment, carry out carbon footprint accounting, and guide silk enterprises to conduct energy-saving and emission reduction green production. Although raw silk inspection is a small part of the entire silk product industry chain, it is also an important part. Research on the carbon footprint assessment of this stage is also necessary.
Method The life cycle assessment (LCA) method under the framework of ISO14067 and ISO14040/44 was used to calculate and compare the carbon footprint of the traditional and electronic inspection of raw silk. The primary activity data including the electricity, material and other additive inputs were collected in the most representative silk inspection agency in China. The Monte Carlo method was used to assess the uncertainty of the accounting results through computer simulation.
Results The system boundaries of traditional and electronic raw silk tests were established as shown in Fig. 1 and Fig. 2, where the main inputs for the two testing methods were almost the same with only slight differences in unit processes. The primary activity data of each unit process are collected and recorded, as shown in Tab. 1. The GHG emission factors of different energy and material inputs were listed(Tab. 2). The carbon footprint (CFP) was calculated by multiplying the quantity of the material input and GHG emission factor of the material. The CFP distribution of raw silk inspections consisting of different unit processes, as well as corresponding CFP percentages of different inputs for different inspections(Fig. 3). The results indicate that the proportion of electricity consumption was the largest, followed by gasoline used for transportation, and the electricity consumption was mainly due to the operation of standard atmosphere maintained in the test room. CFP quantification result shows that there are no big differences between the CFPs of the electronic test and traditional inspection, which are 0.233 6 and 0.235 5 kgCO₂e/kg respectively. The difference between the two test methods is mainly the difference between the seriplane test, the cohesion test and the electronic test. The total test time and electricity consumption are basically the same, so the GHG emissions of the two methods are also similar. Greenhouse gas (GHG) emissions mainly come from electricity consumption for maintaining the standard atmosphere in the inspection room. As the winding machine is huge compared with other test devices, the winding tests occupied a larger space in the room with a standard atmosphere, which contributed to 53.07% of the total emissions of the traditional raw silk inspection. Among the three entrusted inspection items, the GHG emissions of the pile test are the highest, reaching 0.014 5 kgCO₂e/kg, and the sericin content test is 0.010 8 kgCO₂e/kg, while the emissions of monofilament tenacity test are small enough to be neglected. The uncertainty analysis shows that the impact of the total weight of each batch of silk on the total emissions is within 3.95% (95% confidence interval). In raw silk inspection, the two unit processes of appearance inspection and weight inspection are conducted on the whole batch of raw silk. Thus the inspectors need to go to the factory to conduct the inspection. Thus, the distance between the inspection center and the factory varies from miles to hundreds of miles. The GHG emissions of the inspector transportation are estimated according to the average distance, and the uncertainty of this estimation was computed using the Monte Carlo method through Visual C++ programming. The uncertainty percentages of this estimation to the total CFPs of the two test methods are 0.41%, and 0.4%.
Conclusion The calculation results showed that the two test methods yielded almost the same results in GHG emissions, and the GHG emissions during raw silk inspection were largely from electricity consumption. Therefore, effective ways to reduce GHG emissions seem to improve the space utilization rate of the standard atmosphere room, increase the inspection batches and control the cooling or heating temperature of the air conditioner. This study established the estimation and allocation methods of primary activity data collected, CFP accounting and the uncertainty analysis method in the process of raw silk inspection, which provided data and a method reference for CFP accounting in the silk industry.

Key words: raw silk inspection, carbon footprint, quantification, life cycle assessment, greenhouse gas