Life Cycle Assessment (LCA) for Supply Chain Optimization: Comparative LCA of Cotton, Polyester and Regenerated Cellulose Fibers

In this study, water consumption was evaluated using the water footprint concept (Figure 1). Blue water represents surface water and groundwater consumed during fibre production, green water refers to rainwater stored in the soil and utilized by crops, while grey water represents the volume of freshwater required to dilute pollutants to acceptable environmental standards. Cotton production is dominated by blue and green water consumption because of irrigation and agricultural cultivation, whereas polyester manufacturing mainly consumes blue water during industrial processing. Regenerated cellulosic fibres require comparatively moderate amounts of blue water, particularly during pulp processing, fibre regeneration, cooling, and washing operations.

Cotton based production is a water intensive program. For producing 1000 kg of cotton fibre, it requires around 2235 m³ of blue water. Maximum amount of water is sourced from groundwater regions, surface water or river water. Around 82% of all the water is responsible for irrigation purpose [5]. But in convention cotton cultivation process the scenario is much more devastating. Only in cotton production phase, it demands around 10,000 to 15,000 L water for per kg fibre. In manufacturing phase, it requires 100-125 L for per kg fibre (Figure 2) [6].

On the other hand, polyester is synthesized through chemical reactions and that process requires a very little amount of water. Per kg polyester fibre requires only 70L in production phase and in dyeing & finishing stage still requires additional water, approximately 70-136L water is required for per kg fibre, in total 100-200L water is demanded for per kg polyester fibre production. This much lower than conventional cotton production and this is one of the advantages for polyester production. Regenerated cellulosic fibres require moderate amount of water. It is situated in between cotton and polyester. The production phase requires 60L for per kg fiber, finishing & dyeing process consumes around 269L of water for per kg fibre production (Figure 2) [6]. Also, fewer amount of clean water is consumed in solvent recovery and cooling phase as well.

Cotton production is significantly consuming higher amount of water than other two fibres. This can be considered as an environmental hotspot for cotton-based textile manufacturing industry.

Cotton requires high amount of land for the cultivation purpose (Figure 3). Around 19.7-to-20.9-meter square land is required for 1 kg cotton fibre cultivation. Organic cotton requires more land because yields per acre is very low than conventional cotton. Polyester is derived from fossil fuel-based feedstocks. It doesn´t require any type of land or animal resources. On the other side huge amount of polyester is getting recycled which eventually lower down the fossil fuel resource usage. But rPET consumes slightly more land than virgin polyester due to energy and infrastructure issue in recycling process. Overall, polyester has the lowest possible impact on land use scenario [7]. On the other hand, regenerated cellulose has the moderate impact. Though it is significantly lower than the cotton cultivation process. It consumes 2.6 meters square for per kg fibre production. They are generated from wood pulp; this step consumes land. Lyocell fibres are highly efficient, almost ten times productive than conventional cotton processing. It requires approximately around 2.16 square meters of land for production of 1 kg fibre.

Chemical use in textiles differs from fibre origin to cultivation process. In generally cotton consumes a huge number of fertilizers, pesticides, herbicides and soil amender [8]. Cotton occupies 16% of all global insecticides’ usages [9], [10]. Per kg cotton fibre require 457g fertilizer and 16 grams of pesticides. The maximum amount of these agrochemicals is needed in cultivation phase. But unlike cotton, regenerative cellulosic fibres don’t require any type of agrochemicals in cultivation, but they require huge amount of chemicals in industrial processing. These chemicals are extremely hazardous for environment. Around 1.48 kg of chemicals are required for per kg viscose fibre production and this requirement is only aligned with pulp conversion and regeneration stages (Figure 5) [11], [12]. Among those, 98.5% chemicals are required in chemical dissolution & regeneration process, it eventually creates a huge environmental risk as well [13]. But currently 70-95% chemicals can be recycled from this viscose manufacturing setups. On the other side, polyester is a synthetic fibre and it is acquired from petrochemical resources. It does not demand any sort of agrochemicals but it requires chemicals for the polymerization reactions and fibre spinning. Approximately 1.2-1.4kg of petrochemical raw material is required to produce 1kg of polyester fibre [14].

But the chemical burdens are not always comparable because of its phase-based use case. For some fibres the chemical burdens are seen in cultivation phase like the cotton fibre, on the other side polyester fibre requires chemical (Figure 6) for the polymerization reaction purposes. Similarly viscose fibre needs maximum portion of its chemical directory aligned in regeneration and production phase. In cultivation phase, cotton fibre is dominating in chemical burden scenario. Similarly in fibre processing phase the most chemical dominant fibre is regenerative cellulose. But the many chemicals can be recycled in this genre of fibre, especially the solvents. Also, the chemical impacts are depending on the functional groups and the environmental factors. Like the impact of agricultural runoff from cotton cultivation is a serious threat for natural wetland’s ecosystem but the value wise it is not seen that much prominent. So, we need to use characterization factors in life cycle assessment for a fair comparison and understanding (Figure 7) [14]-[17].

Energy is needed in two different stages-fibre cultivation and the fibre processing. Cotton farming requires energy in land preparation, irrigation, tractors, fertilizer & pesticides production, transportation and harvesting (Figure 8)[18]. In cultivation stage, per kg cotton cultivation needs around 5.6 MJ energy [19].

For the polyester fibre, the maximum energy is needed for the processing purpose in mechanized processes. Polyester is synthesized from petrochemical. Around 60 MJ electricity is required in raw material extraction and preparation phase. It includes the crude oil extraction phase and refining phase too. In total polyester fibre needs energy of 120-130 MJ/kg fibre production.

Regenerative fibre distributes all the energy usage into two segments-raw material preparation and fibre processing. 65-106 MJ energy is needed for per kg fibre production (Figure 9) [20], [21]. The maximum portion of energy is going to be used in manufacturing phase. Agricultural production phase requires no major contribution.

Here we can clearly see the electricity consumption for the Polyester fibre & Regenerative fibre are seen much higher than cotton fibre (Table 1 and 2). The primary reason is using of different high energy consuming machineries for fibre production and synthesis process.

Every fibre production process must responsible for carbon emission (Figure 11). Greenhouse gases can be emitted from cultivation phase and also from the fibre process & production phase. On average 3-4.5 kg CO₂ can be emitted in the whole cotton production process. Fertilizers and different agrochemicals are responsible for maximum amount of emission in cotton production process. Polyester does not have any cultivation phase but in the process of raw material extraction, it emits GHG. The polyester fibre production is highly energy dependent. The manufacturing phase is highly responsible for emitting greenhouse gases. Similarly regenerative fibres require energy and chemicals in the process of fibre manufacturing.

To broaden the sustainability assessment, recycled polyester (rPET) was included as an additional reference material. Compared with virgin polyester, rPET significantly reduces fossil resource consumption because it utilizes post-consumer or post-industrial plastic waste as its primary feedstock. Numerous LCA studies have reported reductions in greenhouse gas emissions, cumulative energy demand, and fossil resource depletion for rPET production. As shown in Table 4, the cradle-to-gate carbon footprint of recycled polyester is approximately 2–3 kg CO₂-eq per kilogram of fibre, considerably lower than that of virgin polyester (7–10 kg CO₂-eq/kg) [36], [37]. However, recycled polyester may still contribute to microfiber release during use and therefore does not completely eliminate environmental concerns. Consequently, rPET represents an important circular economy strategy but should be complemented with improved recycling technologies, microfiber mitigation measures, and sustainable waste management practices.

The eco-cost assessment presented in this study is based on the environmental prevention cost concept, which estimates the theoretical cost required to prevent environmental damage caused by a product throughout its life cycle. Eco-cost should therefore be interpreted as an environmental performance indicator rather than a direct production cost. The comparison assumes that published prevention cost factors remain applicable across the selected studies [38]. For regenerated cellulosic fibres, solvent recovery efficiencies reported in the literature (approximately 70–95%) were considered when interpreting the overall environmental burden, since chemical recycling substantially reduces the environmental impacts associated with virgin solvent consumption.

Eco cost is an environmental indicator used for explaining the monetary value environmental damage made by a product throughout its life cycle. It explains the virtual cost for reducing the environmental impact as a compensation. It is an indicator added in Life cycle Assessment [8]. Cotton has the high eco cost value. It consumes huge water and chemicals in its life cycle.

Similarly polyester secures second place in these criteria. The main reason behind the costing can be usage of high amount of energy. Energy production leads to huge amount of GHG emission. Another prime reason can be microplastic pollution due to polyester shredding. It is also responsible for destroying aquatic ecology. Regenerative cellulosic fibres are highly chemical dependent. It can impose negative impact through chemical run off. This is also an energy intensive fibre. But the positive thing is the maximum amount of chemicals can be recycled from the production loop. Maybe this is reason behind its lowest eco-cost value.