Calculation and evaluation of cotton lint carbon footprint based on different cotton straw treatment methods: A case study of Northwest China

At present, although there have been many studies on the carbon footprint (CF) of cotton, only a few studies have comprehensively considered the carbon sequestration effect of cotton. The raw material extraction stage of cotton can be divided into two stages: the cotton cultivation-harvesting stage and the ginning stage. During the cultivation stage, cotton plants exhibit a carbon sequestration effect due to photosynthesis, and the biomass produced is ultimately transferred to seed cotton and cotton straw. In this study, quantitative models for carbon sequestration effect during the raw material extraction stage were established based on the carbon sequestration pathways of cotton plants and three treatment methods of cotton straw. The CF allocation principles between main and by-products have been determined as economic relationships and mass relationships. Based on these four carbon sequestration models and two allocation relationships, six different scenarios were proposed to optimize the CF of producing 1 ton of cotton lint during this stage. Results indicate that the CF of 1 ton of cotton lint harvested during the raw material extraction stage was negative in all six scenarios, suggesting carbon reduction. Converting cotton straw into biomass fuel after harvesting sequesters more carbon compared to crushing and returning it to the field. Economic allocation results in a higher CF value for cotton lint compared to mass allocation. The primary contributors to the CF of cotton lint are fertilizer, electricity, and agricultural films. This study offers valuable methodological and technical insights for assessment on cotton fiber textiles, with potential implications for emissions reduction and fostering sustainable development within this industry.