Solid Waste Recycling in Textile Processing Industries: A Case Study of India’s Clothing Hubs

For this case study, three textile zones (north, west and south) of India, specializing in wet processing of textiles were investigated by onsite visits and interaction with their management and compliance teams. A field survey of five textile wet processing industries from each zone was carried out and the waste management data from a total of 15 industries was analyzed. To maintain confidentiality, each industry in respective zones is named anonymously in alphabetical order as follows: Five textile processing units located in the west zone (Surat) are named A, B, C, D, and E. The processing mills in the North zone (Delhi NCR region) are labeled as F, G, H, I and J, respectively. Textile manufacturing units in the southern areas of India are named K, L, M, N and O. The field survey of all 15 textile mills was done following the audit protocols mentioned in ISO 14001:2015 standard [25]. Solid Waste Generation in Textile Wet Processing Mills The main objective of this case study was to investigate the solid waste produced in textile processing industries in pretreatment, dyeing, printing and finishing stages. Table 1 indicates the waste produced in each sector of the respective zone surveyed for this study. The core processing stages carried out in wet processing industries of respective zones, along with their annual production, are indicated in Table 1, Table 2 and Table 3 . The quantity of waste produced is recorded from waste challans and bills issued by the authorised waste handlers. The textile industries are also maintaining waste registers to fill requisite forms of the Pollution Control Board (PCB). The relevant data of recorded waste is taken from these registers as well. Waste generated in facilities (hazardous and non-hazardous) is validated through the waste handler agreement, waste handler site visit report, transaction vouchers, and manifest copies. As indicated in Table 1, Table 2 and Table 3 there are common categories of solid waste generated in all three zones. Excess cloth cutting, fabric waste, and loose fibres produced as a result of rejects from the quality department are the most prominent categories of solid waste generated in textile wet processing. These fabric waste/cloth cuttings are produced in large quantities in the processing departments of the mills and then thrown away (Figure 1). Other primary sources of solid waste generation are combustible fuels. Wet processes like bleaching fabrics, printing and finishing require extreme temperatures up to boiling (100 °C). Some processes, like polyester dyeing and cotton printing, require steam generation. In India, it is observed that coal is the primary choice for fueling boilers used for steam treatments given to fabrics. Coal combustion residues like fly ash, bottom ash, and boiler slag are other major solid waste components produced in textile wet processing industries (Figure 2). Plastic waste arises from packed plastic films and incoming raw materials like yarns and greige fabric. Discarded shade cards, dyeing/printing recipe cards, and other stationery contribute to paper waste in the processing units. Waste of machinery spares makes for the metal waste produced in industries. Other solid waste generated in textile industries is from waste tube lights, biomedical waste, empty chemical drums, carboys and waste cartons used in the facility. Zone-wise Illustration of waste generated in textile processing mills. Figure 3, Figure 4 and Figure 5 indicate the share of solid waste generated from different sources in the north, West and south zones, respectively. As shown in Figure 3, the major sources of solid waste generation in textile industries are discarded fabrics followed by combustible fuels. Out of the total waste produced by the textile industry, about 27% of solid waste is from fabrics. Ash residues resulting from coal and biomass combustion collectively account for 14.9% of solid waste. The solid sludge resulting from effluent treatment plants at the end of wet processing is another major hazardous waste produced in textile wet processing industries, accounting for 14.9% of total solid waste generated. The western and southern zone textile processing industries show similar trends in waste produced. Cloth cuttings and fabric waste account for 44.9% and 43.7% of solid waste generated in the west and south zone, respectively. Fly ash produced by the combustion of pulverised coal used in boilers of textile mills adds to 29.1% of total solid waste. In addition to coal, most of the textile mills located in the southern zone of India also use biomass as a fuel source. Like coal, biomass derivatives like briquettes, rice husk and other agro-wastes produce ash residues on burning. This biomass ash accounts for 31.8% of total solid waste generation. The recorded values of sludge in the north and south zones were less than those recorded in the west zone. The documented value of sludge is minimal in the western and southern zones. Thus, the data from all three zones indicates three main categories of solid waste: Cloth cuttings (Fabric waste), Fuel combustion residues (Coal fly ash, biomass ash etc.) and sludge resulting at the end of wet processing. Other waste categories like plastic, paper, electronic and biomedical waste have a negligible share in total waste produced in the textile wet processing industries. Influence of fuel sources and water consumption on solid waste generation. The input fuel sources used in processing stages and corresponding waste generated in individual industries are recorded in Table 4. Biomass and coal are measured in metric tons (MT). The tabulated values of LPG and Diesel in Table 2 are measured in litres. PNG and electricity are expressed in Metric Million British Thermal Units (MMBTU) and Kilowatt (KWh) hours, respectively. Except for biomass and coal, all other energy sources are cleaner fuels. LPG, PNG and Diesel burn without producing any residues. So, these cleaner fuels do not contribute much to solid waste generation. In the west zone, annually, 68,230 metric tons of coal, 2570 litres of liquefied petroleum gas, 20,494 MMBTU Pressurized natural gas (PNG), 14,927 litres of Diesel and 22,874,407 kWh electricity are consumed for fueling textile wet processing operations in the 5 surveyed industries. Among these fuel sources, 68,230 metric tons of coal on combustion produces 61,979 kg of combustion residues. These are mainly boiler slag, fly ash, and bottom ash. On the other hand, in the northern and southern zones, coal is partially substituted by biomass fuel sources. These can be agro-based waste, briquettes, wood pallets and other biomass fuel derivatives. Like coal, on combustion, these biomass-based fuels also produce solid waste, i.e. biomass ash. In the northern and southern zone, biomass ash contributed to the generated total solid waste in addition to coal combustion residues. The textile wet processing is a highly water-intensive segment. Wastewater emerging at the end of processing is passed through a series of effluent treatment chambers. The solid sludge generated after the effluent treatment sequence is proportional to the input water required for processing. Table 5 depicts the amount of wastewater consumed in textile wet processing annually in all three zones. Textile processing factories rely mainly on municipal supply of water for production activities. In addition to municipal freshwater supply, groundwater reserves are utilised to meet the water consumption needs of textile mills. Treated wastewater from a common effluent treatment plant (CETP) is utilized again in processes where water quality is not required. Solid sludge arising after consuming such hefty volumes of fresh water is another concern for disposal. Textile sludge constitutes a high concentration of heavy metal elements. Thus, landfilling sludge is detrimental to the environment. Landfilling is the primary method of disposing of textile sludge at the moment [26].