Recycled polyester ( PET ) - polyethylene production description / energy considerations
MATERIAL The source material (bags of rice sized pellets), is forced under pressure through tiny nozzle openings, creating a very thin continuous filament. Many of these filaments are then weaved together into a stronger bundled filament that is called yarn. The normal look for these petrochemical yarns is a slightly off white colour, although with different recycled source pellets, other colours are possible.. As the yarn is created it is rolled onto huge spools that look much like a standard thread spool, except they weight about 50 lbs and are about 1 cubic foot in volume.
WEAVING The next step takes 40 to 60 of these spools, and weaves them together into fabric. The weaving machines are about 4m by 6m and are extremely noisy. In a normal weaving facility there are between 50and 200 of these machines. Most of the yarn spools used are for the forward direction, (the warp), and a few for the side-to-side direction (the weft). A completed fabric roll is 1.8m wide and about 100m long, so most of the yarn is used for the warp. The weft yarn can be moved by an air or water shuttle mechanism. The actual weaving process is based on simple ideas that have been developed over centuries. Slowly the warp yarn moves forward, separated by tiny pins. There are 2 horizontal layers of yarn ( every second yarn is in one layer), and they act independently. With one layer up, and one down, the weft shuttle moves sideways across the warp, the two layers swap their up/down positions, and the weft shuttle returns to the starting position. By repeating this process thousands of times fabric is created. The raw fabric (called greige or ‘unfinished’), can be many different thicknesses and have many patterns, depending on the weight of the yarn used, the source material, and the number of yarn spools used. The pattern is determined by adjusting the layout of the pins. A finished industrial fabric roll weighs about 1-2000kgs, and is moved by an overhead industrial gantry lifting system.
DYEING Once the raw/greige fabric is produced, the next step is the color dyeing. Fabric is run through a dipping tray of chemical colour. Many different chemicals are used, some of which are environmentally benign and others that are not. After dipping,, the fabric is placed in enormous industrial dryers, much like your home clothes dryer. Nylon fabric needs to be dried at a hotter temperature than polyester fabric in order to get a proper ‘set’ between the dye and the fabric. Unlike cotton that readily absorbs organic dyes, nylon and polyester dyes are synthetic. The energy used to dry the freshly coloured fabric is the largest overall energy requirement in the production chain.
COATING #1 After a quality control examination of the now colorful fabric, it is run through a large 6m x 30m coating machine. The fabric is run under a layer of this liquid coating, as it is only used to coat one side, and then continues through the machine in a second drying process. This process also uses a large quantity of heat/energy. The shortest piece of fabric that can pass through one of these machines is 100m. When looking at a finished nylon/polyester product, this coating is the inside of the material, and it is often not visible. The backing gives the fabric stiffness and form, otherwise your backpack or bag would have no definite shape. The standard fabric backing is polyurethane (PU). Sometimes fabric is run through this machine twice for added stiffness. More environmentally friendly water based coatings are available to replace the solvent based PU coatings, at a higher cost.
COATING #2 Some textile manufacturers now add a final production step, which consists of one more chemical coating. These coatings are added for a number of reasons. Three of the major motivations for adding it are to prevent UV degradation in lifejackets, prevent mould and mildew forming, and to add water absorption resistance to your rain clothes. Not all fabrics have this treatment added. After a final quality check, the huge initial rolls are now wound into smaller 50-100lb rolls and shipped off to a product manufacturer.
ENERGY IN TEXTILE PRODUCTION Energy is used for all the steps of the fabric production process. Large quantities of electricity are required to run the machines, and large quantities of heat are required to dry materials. Comparatively, the actual production of finished textile products requires comparatively less energy. For this reason, production of textile products is often done in developing countries that have limited low cost energy sources, like Vietnam, China, and the Phillipines. The production of the fabric material is more often in more higher developed countries like South Korea, Taiwan, Japan and the USA. Large amounts of energy can be saved in the production of textile products by using recycled PET (polyethylene) materials. Little additional energy and no new chemicals are required to create the source pellet raw material. The best possible energy situation is when “disposable” water bottles are collected, upcycled, (taking a one-use product and turning it into multiple-use product with a 5-20 year lifespan), and finally produced into a finished product all in the same country. Unfortunately, this is not always possible. Quality upcycled PET fabric has exactly the same tear strength, abrasion resistance, and durability as new polyester fabric. The same characteristics that cause us great concern when disposable bottles are dumped into landfills (resistance to degradation and strength), as well as their lightweight characteristics, can be used to our advantage to make long-lasting consumer products. Reducing packaging is another way of easily reducing the energy requirements of textile products.
SHIPPING CONSIDERATIONS Energy requirements for shipping finished goods from Asia to Europe or North America can also be reduced in many ways. Container ship fuel efficiency comparisons are available. Textile producers that are environmentally aware may choose cargo ships based on their-energy efficiency. These ships can use up to 50% less fuel then most of the container fleet. The majority of this reduced fuel requirement is due to low friction paint technology, and modern engine designs. Fuel consumption of all ships could also be reduced by a further 50% by simply reducing the speed of their intercontinental journeys. From a manufacturers point of view this would have little impact on business, as I would simply have orders placed 30 days earlier. Obviously the ship owners would have less billing cycles in a calendar year, however many companies that care about creating the most sustainable business model would pay more for ships that go slower. This then puts pressure on shipping companies to invest in high efficiency technologies to take advantage of the market the environmentally conscious manufacturers provide. In 30 days of travel, a container ship emits the same amount of pollution as 50,000 small cars do in 1 year. Finally, the lowest quality, most polluting form of oil on earth is used to power these ships. Due to lack of government regulations regarding ocean travel, there are very few emission requirements for ship owners to meet. Adding emission port taxes for the most polluting ships, or port fee reductions for the least polluting would help reduce this pollution.
SUMMARY The benefit of using upcycled PET material for textile products is a reduced environmental impact on the planet. However, there is still an impact. An important factor is the quality and durability of the textile product, and there is no benefit from using inferior materials just because they are recycled. Any PET product you purchase must be as long lasting and durable as one produced from new materials. Often textile products fail along seam lines, on or near the zippers, and at structural reinforcement points. This is due to a lack of knowledge by designers and manufacturers. The lifespan of a product can be greatly enhanced by treating this issue seriously during product development. It is also very important to know where the power came from to upcycle the water bottles. One American recycler uses energy produced from coal fired power-generating stations, in this case the benefits of using recycled fabrics is greatly reduced. The only truly sustainable purchase is none at all. However, as we are all aware, it is not always possible to avoid the market economy entirely. As a consumer it is your responsibility to make informed choices, purchase long lasting products, and support companies that contribute to environmental and social sustainability programs.