Carbon Footprint Assessment And Low Carbon Measures Of The Polyester Textile

Product carbon footprint is the greenhouse-gas (GHG) emission of one product throughout the whole life cycle ranging from raw material production to production (or service), distribution, use, and disposal/recycling. GHGs include carbon dioxide (CO2), methane (CH4), nitrogen monoxide (N2O), hydrofluorocarbons (HFC), perfluorocarbons (PFC) and so on. The global climate change related to carbon emissions has attracted increasing attention, and then so does the environmental impact caused by production and consumption. Carbon footprint makes one fully understand the carbon emissions at each stage in the life cycle, promote people to take controlling measures,and guide the low-carbon consumption behavior. Textile is a common kind of daily necessities and industrial products, but the assessment about its carbon footprint is in infancy. The subject attempted to assess the carbon footprint of domestic textile, with the purpose of initially grasping the quantitative emissions data of domestic textile, based on which some low-carbon measurements will be put forward and evaluated quantitatively to benefit,in some degree, the low carbon emission of textile industry.According to the the definition on "from cradle to gate" in BS EN ISO 14040 and the assessment method of product carbon footprint recommended by PAS 2050 Specification Guide the subject preliminarily established carbon footprint assessment model of textiles. By GaBi Education 4 Life cycle assessment (LCA) software, we calculated the carbon footprint of polyester fabric "from cradle to gate" (i.e., from raw material production to the delivery after dyeing), analyzed and determined the key factors of polyester fabric carbon emissions, and then proposed some low-carbon measures about the key factors. Finally, those measurements were evaluated by means of a simple assessment model.The model included the determination of the purpose, mapping of product life cycle process, data collection and calculation of carbon footprint. During model application,100kg polyester textiles was selected as a functional unit. Complying with the calculation steps of GaBi Education 4 Life cycle assessment software, the polyester textile production "from cradle to gate" was decomposed into six main stages:the production of ethylene, the production of ethylene glycol, the production of p-xylene, the production of terephthalic acid, the production of polyester filament, weaving and dyeing process. The six major processes contains several smaller production processes, which are mainly electricity production, industrial water production and so on.Accordance with the above model, by GaBi Education 4 life-cycle assessment software, calculated carbon footprint of 100kg polyester fabric was 2570.10kg CO2e. Thereinto, ethylene production of carbon emission was 53.29 kg CO2e; ethylene glycol production carbon emission 36.96kg CO2e; p-xylene production carbon emissions 27.14kgCO2e; terephthalic acid production carbon emission 103.09kgCO2e; polyester filament production carbon emission 696.11 kgCO2e; weaving and dyeing process carbon emission 1654.4kg CO2e. Through analysis, it was concluded that the carbon emission during printing and dyeing of polyester fabric mainly impacted the carbon footprint, accounting for 60% of total carbon emission, while the steam contributed to 70% of carbon emission of dyeing process. Therefore, the steam of dyeing production was a key factor in low-carbon control. In addition, electricity production in the set life cycle range also was responsible for a large proportion of the total carbon emission, and proved to be another important factor to control carbon emission.Based on the above analysis, the subject discussed the low-carbon measures of polyester fabric from the perspectives of energy and technology. In terms of energy sources, two simple computational models were respectively designed to assess quantitatively the carbon footprint changes of steam production and electricity production before and after changing energy sources. It was deduced that the carbon emission of 100kg polyester textile was decreased by 772.19kgCO2e when coal was replaced by nature gas to produce steam. Assuming that wind power was used to produce electricity to substitute thermal power, it was found that coal-burning power's carbon footprint was 277.8 kgCO2e, while wind power's carbon footprint was 2.588kgCO2e in the case of the same generating capacity. Since the polyester fabric dyeing is still dominated by high temperature and high pressure method, which is a traditional high energy-consuming and high carbon-emission process. By UV laser modification, the temperature of polyester fabric dyeing can be lowered, and the use of dyes reduced, with a certain low carbon potential. The carbon footprint calculation showed that, under the premise of little change in color fastness and K/S value, the carbon emission of unmodified fabric dyeing was 11.47kgCO2e, while the carbon emission of laser-modified fabric dyeing was 14.48 kgCO2e. Obviously, the latter was greater than the former, contrary to expectation. However, this does not negate the low-carbon potential of laser-modified polyester fabric because the usage of fabric under laboratory condition is little, but the laser power is high. If under the industrial-scale production condition, the laser may be able to treat a large number of fabric in short time, then the power consumption per unit will be reduced significantly, so it is likely for UV-laser modified fabric to have low carbon and low environmental impact under the conditions of industrial production.