Sustainable technology refers tothat which caters to the needs of the present without compromising the abilityof future generations to meet their own needs. It enables more valuable use ofnatural resources and greatly reduced ecological impact among othertechnological benefits. Though sustainable technology deals with energyefficiency, reduction in pollution, use of renewable sources, it should also beeconomically sustainable too, says Avinash Mayekar.

 

The consumption of naturalresources has increased exponentially in the past decades in rapidlyindustrialising countries and it is rather recently that we have startedrecognising the unpleasant consequences of the carefree attitude towards theenvironment.

 

The textiles industry is among themost essential consumer goods industry in the world, as it fulfils one of thebasic needs of human beings. Today, the world of fashion is glamorous andstylish; however, its impact on ecology is worsening day-by-day. The textilesindustry is condemned as being one of the most polluting industries in theworld. Not only production, but even consumption of textiles produces waste. Atevery stage of textile production, vast amounts of energy, clean water andchemicals are used to process textiles and apparel. In turn, these processesgenerate air, water and soil pollution through untreated effluent generationand waste generation which place a heavy burden on the environment.

 

More than 2,000 types of dyes,chemicals and other auxiliaries are used in the textiles industry. The WorldBank estimates that almost 20 per cent of global industrial water pollutioncomes from the treatment and dyeing of textiles. Some of the toxic chemicalscannot be filtered or removed. Dyeing, washing and after-treatment of textilesrequires large amounts of fresh water. Cotton production accounts for 2.6 percent of annual global water usage. A single T-shirt made from conventionalcotton requires 2,700 litres of water and a third of a pound of chemicals toproduce. Millions of gallons of wastewater discharged by mills each yearcontain chemicals such as formaldehyde (HCHO), ammonia, chlorine, heavy metalssuch as lead and mercury and other pigments. These chemicals cause bothenvironmental damage and human disease. Effluents released from mills are oftenat high temperatures and have high pH (salinity), which exacerbate the problem.


Conventional cotton is highly dependent onpesticides, herbicides and fertilisers to grow. In many regions, insects limitcotton production and some of these pests become resistant to pesticides. Notsurprisingly, cotton pesticides and herbicides account for 10 per cent of allagricultural chemicals and 25 per cent of all pesticides used worldwide eachyear. Untreated dyes cause chemical and biological changes in our aquaticsystem, which threaten species of fish and aquatic plants. The presence ofthese compounds also makes practical water use unhealthy or dangerous. Theenormous amount of water required by textile production competes with thegrowing daily water requirements of the half billion people that live indrought-prone regions of the world. By 2025, the number of inhabitants ofdrought-prone areas is projected to increase to almost one-third of the world'spopulation. If global consumption of fresh water continues to double every 20years, the polluted waters resulting from textile production will pose agreater threat to human lives.

Today, the growing awareness of environmental issues makes customers select eco-friendly products over conventional ones. While end-consumers of textiles were earlier concerned with only the finished product, there has been an increasing drive to better understand the input materials, the relevant production processes, and their implications on the environment - be it air, water or soil. Ignorance and indifference to these will no longer remain an option for the textile supply chain. So, it has become imperative that the textiles industry should address issues within our supply chain and adopt better and cleaner technologies. Moving to a greater degree of sustainability in industrial processes and systems requires that we achieve better balance between social, economic and environmental aspects of textile production. With increasing awareness of environmental issues posed by the textiles industry, many technology providers are working towards the improvement of technology to reduce the environmental damage created by the textiles industry and reduce consumption of energy, water and chemicals.

 

The textile wet processing industry is now in the spotlight due to the recent Detox campaign by Greenpeace and will have to align with the goal of Zero Discharge of Hazardous Chemicals by 2020 that is being pursued by several leading international brands and retailers.

 

Following are the technologies currently being used worldwide as a response to sustainability:

 

Exhaust piece dyeing: A combination of advantages of long tube machine design with aerodynamic fabric transportation principle has been developed by 'Then' with their new development - the Then Airflow Lotus machine which is the world's first long tube machine to operate using the original aerodynamic principle. The objective of the development was to create a system that would be especially suitable for the wet processing of delicate, easily creased, cellulose and synthetic fibre knits and wovens with a high percentage of elastane fibre, which are used in the lingerie, sport, leisure and swimwear segments. Resource benefits focus on ultra-low liquor ratio 1:2 to 1:5 with associated reduction in water demand, effluent volume and loading from reduced salt consumption when reactive dyeing and a reduced energy requirement. Fong's have further refined their Jumbo Flow machine with Advanced Intelligent Rinsing (AIR) with the option of a conductivity measurement to detect when the concentration of electrolyte has reduced after reactive dye processing to a concentration where the rinsing is transferred to the soaping stage, thereby optimising water consumption. 'Thies' have further developed their EcoMaster machine incorporating multi-contact dyeing from the double liquor: fabric interchange design to permit reduced dyeing times and low liquor ratios from 1:3 for synthetics to 1: 4.5 for cotton fabrics, and an auto control of the rinsing procedure using Rinsetronic software to further reduce process times and water consumption.

 

Cold pad batch dyeing: For vertical knitted fabric operations, there is a renewed interest in reactive dye application by cold pad batch application due to the lower consumption of water and reduced effluent loading, with a claimed reduction in variable costs of 15-30 per cent. The resultant fabric has a much cleaner stitch definition due to no surface abrasion, and to produce a similar g/ sq.m fabric as exhaust dyeing, an increase in stitch density should be considered at the knitting stage if the cold pad batch application route is ended. Developments in machine design are mostly for open width processing using sophisticated auto-centre and edge uncurling devices but also include dosing pumps, low-liquor troughs and configurations to allow dye application in the nip as well as in the low-liquor trough. Also, on modern pad rollers the pressure can be adjusted across the full width to allow uniform liquor pick-up to eliminate side-centre-side variation. Integrated heating and cooling systems have also been developed to ensure constant temperature in the pad trough regardless of the time of day/season and thus improve the reliability of the process re-liquor stability/ hatching time.

 

Continuous dyeing: The Econtrol process utilises the innovation of the Thermex Hot Flue from Monforts. The innovation exploits the thermodynamics of water evaporation from cellulose to provide the optimum temperature and moisture conditions within the hot flue dryer ideal for the efficient fixation of the specially selected reactive dyes. Monforts have in conjunction with DyStar further developed the successful Econtrol process and at ITMA Munich in 2007 launched the new Econtrol T-CA process for the colouration of polyester/cellulose blends. This development combines the humidity control for reactive dyes with a Thermo sol unit for application of new Dianix T-CA disperse dyes and a new auxiliary package which obviates the need for an intermediate reduction clear process. The savings in chemicals, water, and energy are significant. Along with newest machine technology, the right dye selection also places an important role and hence to maximise the synergy between innovative machinery design and application process to deliver productivity, cost efficiency, and environmental benefits, it is critical to optimise dye selection.

 

Energy efficiency

Energy efficiency is an integral part of sustainability. For many years textile finishing has operated with chemical and thermal processes which, by present-day standards, can have a severe impact on the environment. The energy costs are high, and the use of chemicals absolutely essential. But with innovative ranges and advanced auxiliaries, Monforts has succeeded in optimising these processes. The savings benefits that have been achieved in recent years are in some cases, quite considerable.

 

An excellent example highlighting how the Blue Competence concept can influence R&D activities is the Matex Eco Applicator - a unit which significantly reduces the initial moisture content before the drying process. The challenge of sustainability is to save natural resources without compromising production quality of the final products. The Eco Applicator ensures reduced energy consumption, faster drying and higher productivity compared with standard equipment such as padding systems.

 

Padding is a process employed in the textile industry for wet treatment of textiles. The fabric or 'substrate' is transported through a trough containing the finishing or dyeing liquor. The term 'liquor' is generally used to refer to an aqueous liquid in which textiles are washed, bleached, dyed or impregnated. It contains all the dissolved, emulsified or dispersed constituents such as dyestuffs, pigments or chemicals. During the further course of the production process, the substrate is transported through rollers to remove the excess liquor. A liquor absorption of 70 per cent - which is a typical value in standard padding application - means that 100 kg of textile fabric has to absorb 70 kg of liquor. After the impregnation process, the wetted fabric is dried in a final step by means of a Montex stenter. For this process, drying energy is required which, in the textile finishing industry, is a major cost factor. Influencing factors for the energy consumption and costs of drying processes are the initial moisture content, residual moisture content, drying temperature and relative water vapour content of the ambient air. The degree of initial moisture is the crucial point for determining how much evaporation heat and energy is necessary for drying.

 

Reduction of the liquor pick-up, which is the means of operation of the Monforts Matex Eco Applicator, results in less evaporation of heat and lower operating costs. With the Eco Applicator, the liquor is not applied to the fabric by dipping it through a trough but by using steel rollers which transfer the required amount of liquor onto the fabric. With lower waste water contamination the application unit becomes a resource-conserving alternative to padding.

 

Recent developments

Brazzoli has developed a 'Green Label' version of its InnoEcology fabric-rope-dyeing machine, which it says is geared to reducing consumption of water, steam, energy and chemicals, as well as to increasing machine productivity, while maintaining the final product quality. As an example, Brazzoli says a jersey fabric that, in 2011, on an earlier generation of the machine, required 35 litres of water per kg/ dyed can now be processed with only 28 litres. The carbon footprint has been reduced to 1.51 kg/CO2 per kilo of fabric, equal to 0.5 kg/CO2 per T-shirt. In India recently, Alliance Machines Textiles of France, displayed a new dyeing machine that uses air technology to reduce water usage. The new, low-liquor-ratio Riviera Eco+ Green is a single-tube machine that uses air to rearrange the fabric at each revolution, just before it comes into contact with the liquor. This is said to avoid creases, especially on delicate fabrics. The air is not used for fabric transport.

 

Meanwhile, Monforts is shortly to launch a retrofit heat-recovery system for its Montex stenters. This will allow existing users to achieve the same energy gains as with new machines, where the system comprises a compact, air-to-air heat exchanger, installed within the roof structure of the stenter. This uses energy from the exhaust gas to preheat up to 60 per cent of the incoming fresh air entering the stenter and depending on production conditions, delivers energy savings of 10-30 per cent.

 

Future of textiles industry

In conventional textile dyeing, large amounts of water are used both in terms of intake of fresh water and disposal of wastewater. On average, an estimated 100-150 litres of water is needed to process 1 kg of textile material, with some 28 billion kilos of textiles being dyed annually. Water is used as a solvent in many pre-treatment and finishing processes, such as washing, scouring, bleaching and dyeing. Hence, the elimination of process-water and chemicals would be a real breakthrough for the textile dyeing industry, and it seems this has now come to fruition, with the launch of the world's first ever industrial dyeing machine that uses super carbon dioxide as a replacement for water.

 

When carbon dioxide is heated to above 31°C and pressurised to above 74 bar, it becomes supercritical, a state of matter that can be seen as an expanded liquid or a heavily compressed gas. In short, above the critical point, CO2 has properties of both a liquid and a gas. In this way, supercritical CO2 has liquid-like densities, which is advantageous for dissolving hydrophobic dyes and gas-like low viscosities and diffusion properties, which can lead to shorter dyeing times compared to water. Compared to water dyeing, the extraction of spinning oils, the dyeing and the removal of excess dye can all be carried out in one plant in the carbon dioxide dyeing process which involves only changing the temperature and pressure conditions; drying is not required because at the end of the process CO2 is released in the gaseous state. The CO2 can be recycled easily, up to 90 per cent after precipitation of the extracted matter in a separator. DyeCoo Textile Systems BV has achieved the unachievable, emancipating the world of fabric manufacturing from the troubles of water-based textile dyeing process for once and for all. A dyeing machine named 'DryDye' that utilises CO2 instead of water and extra textile chemical agents is a highly innovative waterless textile dyeing breakthrough achieved by the Dutch company.

 

CO2 dyeing technology has become more intelligent and energy efficient with the discovery of the DryDyedyeing machine. Though the waterless dyeing technology using CO2 was invented in Germany almost two decades ago, no commercially viable machine was developed until now. DyeCoo Textile Systems is undoubtedly the laurelled victor acclaimed by the textile techies around the globe. Though the machine is capable of dyeing polyester at batches of 100-150 kg, work is under progress to accentuate the functionality of the waterless textile dyeing machine. The day is not far when reactive dyes for cellulosic will be used resulting in greater all round efficiency and a better fabric dyeing.

 

In conclusion

If we see awareness on hazardous effluents generated and amount of energy consumed during the entire manufacturing process of textiles and apparels among end-consumers, it is still limited. Many of them are not even aware that some of the dyes and chemicals used are carcinogenic and life-threatening. Some retailers and brands in Western countries have taken a green initiative to produce goods in a sustainable manner. On the contrary, there is very little awareness among Indian manufacturers and end-consumers about the harmful impact on environment. Some processing units are still discharging untreated effluents which are polluting water bodies. Some dyes and chemicals can even cause chronic diseases. It is very important to generate awareness among textile manufacturers and end-users. The entire textile value chain should take the initiative to manufacture goods economically through sustainable processes and technologies with minimum or no impact on environment or consumer. Technology is a key to reach sustainability targets of the textiles industry.

 

With volatile commodity and energy prices as well as requirements from brands, retailers, consumers and governments, sustainability has become a significant competitive factor for textile manufacturers. Sustainability is an issue with hard economic aspects. It has become a significant competitive factor. Technological upgrading is one of the keys to realise sustainable textile production, and so remain competitive. Some of the remarkable innovations in technology have paved the way for sustainable production technologies, but there is a huge scope further for all technology providers to upgrade technology which will help in economical production of the goods in a sustainable manner.