As a leading flat knitting machine manufacturer, STOLL is challenging the conventional circular T-Shirt production process with our latest innovation: a machine capable of producing the finest possible gauge.
We recognize that the productivity of flat-bed knitting machine may not match the productivity of circular machines , nonetheless we believe that our solution is a more sustainable one. We strive to challenge the circular made T-Shirt production that is normaly a cut & sew process with lot of waste material.
Our focus on sustainability is particularly important in the context of T-Shirt production, as it is a mass-produced garment that can be worn in warm climates and functions as both an underwear layer and a mid-layer, suitable for year-round use. With our new machine, we are able to produce a high-quality T-Shirt made using carbon-zero TENCEL™ Lyocell fibers.
In a joint project with Lenzing, we aim to demonstrate the maximum reduction and carbon impact calculateion along the value chain based on a Low Carbon Concept Shirt.
By reducing waste, CO2 and taking biodegradability into account, we are taking a step towards a greener future, and we invite you to join us on this journey.
Image Source: Lenzing AG
Besides the knitting process to create the textile surface, the primary element to ensure product sustainability is the material. TENCEL™ is the textile premium brand under the Lenzing Group covering textile product offerings, defining a new step on sustainability and natural comfort. Its specialty fiber can be used for a variety of highly specialized apparel and home textile applications. TENCEL™’s latest ‘True Carbon Zero’ journey includes bold commitments to the Science Based Targets initiative to slash greenhouse gas emissions per product ton by 50% by 2030 and become carbon zero by 2050. To support this, TENCEL™ developed carbon zero TENCEL™ branded fibers in 2020.
Carbon-zero TENCEL™ Lyocell and Modal fibers are certified to reduce climate impact as the fibers are biodegradable, reducing carbon emission and reaching new levels of sustainability to meet the needs of Lenzing’s brand partners.
The fibers are derived from sustainably sourced renewable raw material wood following the stringent guidelines of Lenzing Wood and Pulp Policy, and are produced using environmentally responsible processes that do not use toxic chemicals or produce harmful waste. As such, carbon-zero TENCEL™ Lyocell fibers contribute to the reduction of the carbon footprint of the supply chain by engaging with value chain partners and making Lenzing’s goal of carbon neutrality a collaborative mission.
The following figure is intended to visually illustrate further advantages of Lyocell.
Image Source: Lenzing AG
In order to make a meaningful and useful statement regarding to the CO2 emissions of the T-Shirt, each individual sector required for the production must be analyzed.
The use of carbon-zero TENCEL™ Lyocell fibers demonstrates the commitment of STOLL and the TENCEL™ brand towards enabling a carbon neutral textile industry.
With a vision to achieve net-zero emissions by 2050, the TENCEL™ brand’s three-step plan is already in action: reduce, engage and offset. The plan strives to reduce carbon emissions through more efficient production methods, engage the industry to source botanic and biodegradable materials with low carbon footprints and offset unavoidable carbon emissions, like those incurred in transportation of the fibers by supporting verified global carbon reduction projects.
From Pulp Production to Spinning, Finishing and the Make-Up, it should be noted that for sustainability reasons, the product is not dyed. The following illustration shows each production step that has been analyzed.
Lenzing is committed to procuring wood and dissolving wood pulp exclusively from non-controversial sources. Wood for TENCEL™ fibers comes from regions such as Europe, the USA, Brazil, Chile and South Africa - for details see Lenzing Wood & Pulp Focus Paper.
The CO2 footprint of carbon-zero TENCEL™ Lyocell fibers was reduced by using a cleaner energy mix and investments in increased production efficiency. The few remaining emissions that could not be reduced were offset by supporting high-quality carbon reduction projects around the world, in communities impacted by the textile industry. Carbon-zero TENCEL™ Lyocell fibers are third-party certified as carbon neutral by means of carbon emission reduction and respective compensation measures.
This fiber production for the Low Carbon Concept Shirt started off with carbon-zero TENCEL™ Lyocell fibers produced at the Lenzing plant in Heiligenkreuz, Austria, which are certified as carbon neutral. The carbon footprint of the production of TENCEL™ Lyocell fibers has been independently calculated, verified and fully offset by corresponding CO2e offset reduction projects to achieve CO2 neutrality. The compensated value 2,35 CO2 e kg per kg of TENCEL™ Lyocell fiber* includes the pulp production and delivery transport, as well as an average value for the transportation to the spinning mills.
Therefore the fibers contribute with a total impact of zero CO2e kg per kg to the concept shirt.
* data provided by Lenzing
TENCEL™ fibers are spun into yarn at a spinning mill in Klanjec, Croatia by Linz Textil GmbH.
Conventional machines can process the fiber without difficulty and with only minor adjustments needed to improve processing performance. The yarns are made of 100% TENCEL™ Lyocell fibers produced by Linz Textil GmbH are notably uniform and boast impressive tensile strength.
The CO2 kg equ.per kg yarn is 1,3906. This value was kindly provided by Linz Textil GmbH.
The yarn is knitted on our ADF 530-32 ki BcW E20, a machine capable of producing the finest possible gauge in flat knits.
In order to obtain an accurate analysis of the CO2 consumption of the knitting process, the energy consumption at the machine was measured for each individual knitted part.
The CO2 emission in kilograms of the entire knitting process is 0,6535.
The manufacturer's data were consulted for the emission calculation of the washing process.
It should be noted here that the result is due to a washing program at 60 degrees Celsius. However, the T-Shirt is washed at 30 degrees Celsius.
Thus, the result of 0,0001 CO2 per kilogram is higher than the actual consumption.
The washed knitwear is dried in a dryer for 10 minutes, which creates an emission of 0,0019 CO2 per kilogram.
In contrast to circular knitwear, where finishing takes place by yard goods, the ironing process is of great importance for flat knitwear. In this step, the dimensional stability is ensured.
Especially with thin qualities, which tend to curl quickly, ironing is a decisive process step for good further processing and finishing. In this respect, ironing takes up a large part of the production process.
If we consider the ironing before washing, after drying and the ironing of the assembled T-Shirt, the result is 0,0045 CO2 per kilogram.
The technique of making up with an overlock machine makes it possible to bypass the step of binding the garments. It is also possible to use sustainable sewing yarn adapted to the general product.
Fully Fashion gives the advantage to knit different structures directly in form: By taking a tubular start already into account during knitting, we can narrow down sewing steps for hem processing.
This production process releases 0,0000503 CO2 emissions per kilogram.
Another important parameter that should not be neglected is the transport route and the emissions it causes.
The figure is intended to illustrate the route more clearly.
The carbon footprint of wood pulp (the basis for fiber production) and its transportation is taken into account in the overall fiber footprint calculation for carbon-zero TENCEL™ fibers, produced at the Lenzing plant in Heiligenkreuz, Austria. These fibers are then spun into yarn by Linz Textil in Klanjec, Croatia. This yarn is then transported to Reutlingen, Germany where the production of the concept T-Shirt takes place.
The worldwide average of Lenzing’s transportation from factory to spin mill is 0.22 CO2 per kilogram. The compensated value of 2.35 CO2e per kilogram of fiber accounts for the emissions of transportation.
With the help of an emission calculator, the emission consumption of the covered distance of 751,25 kilometers from Croatia to Germany is determined. It is assumed that the yarn is carried out by a conventinal truck, which is in a weight class of 26-40 tons. In addition, the pollutant class 2 is defined.
The route covered for transportation from Croatia to Germany is 65,027 CO2e per kilogram.
If the waste produced by a flat-knitted textile is compared with a conventional circular-knitted textile, the reduction in waste becomes clear:
In the case of our produced Low Carbon Concept T-Shirt, which was knitted on our new machine, the material waste is 4,783g.
If the waste produced in the manufacturing process is added to this value, the total waste of one T-Shirt knitted on our flat knit machine with a weight of 250g is 1,91%.
If the knitting parts are knitted off one after the other, the use of the comb yarn can be reduced.
In this case, the comb yarn would only be used once and would not be needed for the remaining knitted parts.
The following table visualizes the defined CO2 emissions of the T-Shirt.
It should be noted that the data for transportation, fibre extraction and the data of the spinning process are given in CO2 equivalents.
The CO2 equivalent (also known as CO2e) is a metric measure used to compare the emissions of different greenhouse gases. This is done by converting the amounts of other gases into the equivalent amount of CO2.
The transportation is the biggest polluter due to our calculation.
*The production of carbon-zero TENCEL™ Lyocell fibers has been independently calculated and verified and fully offset by corresponding CO2e offset reduction projects to achieve CO2 neutrality. The compensated value 2,35 CO2e kg per kg of TENCEL™ Lyocell fiber includes the pulp production and delivery transport as well as an average value for the transportation to the spinning mills.
To enhance your understanding of the calculated values, we encourage you to refer to the accompanying graphic that illustrates the carbon footprint of everyday groceries. By comparing our analyzed values with those of our own lives, we can obtain a clearer understanding of the impact that the Low Carbon Concept T-Shirt can have. For instance, the carbon footprint associated with the knitting process of the T-Shirt is lower than the carbon emissions generated in the production of 100 grams of chocolate.
Image Source: statistic.ly
This project was kindly supported by Lenzing AG.
And Linz Textil GmbH.