How Much is Knitting Contributing to Global Warming?
Is Knitting Good for the Environment?
My soon to be published book, Geometric Knit Blankets, features 30 knitted blankets, representing a boatload of yarn. The blankets are knitted in wool, acrylic and cotton and some mixtures of these. The large amounts of yarn used for my samples got me wondering: just how much is knitting, and in particular, the choice of fiber content in the yarn, contributing to global warming?
Carbon footprint of producing yarn fibers
I found several scholarly research papers that give insight into the “carbon footprint” of yarn fiber production. The table below shows the contributions from production of knitting yarn fibers to greenhouse gases in units CO2 equivalents (CO2 -e). The fibers are listed in ascending order of their contribution. Cotton is the winner with the least contribution, and wool is the loser with the most contribution. Organically produced cottons produce less than half the C02 -e as their conventionally produced counterparts. Synthetics appear to contribute much more to global warming than plant based fibers.The gases that contribute to global warming are: CO2, CH4 (methane), N20 (nitrous oxide and N20 (andozone). C02 -e (e stands for equivalents) includes a measurement of each gas emitted, adjusted by its potential to contribute to global warming.
Wool Carding at a US Textile Factory
Merino Sheep Sheering
I could not find a paper that broke down the contributions from wool by animal cultivation vs. fiber production (shearing, cleaning carding, etc.). I was only able to find a total number for C02 -e, and the two sources I found didn’t agree, so I included a range encompassing both numbers.
For comparison, the amount of C02 -e emitted in production of a roll of paper towels is 2.64 kg, and 4 kg CO2 are produced by driving 11 miles in a 25 MPG car.
How much CO2 (greenhouse gas) is generated by the wool in a knitted blanket?
The average blanket in my book uses 3300 yards of worsted yarn which is approximately 1.5 kg. So a blanket knitted in conventional cotton corresponds to 9 kgs CO2-e, an acrylic blanket corresponds to 19 kgs CO2-e, and a wool blanket corresponds to about 30 kgs CO2-e. In car mile equivalents, a cotton blanket is like driving 25 miles, an acrylic blanket is like driving 52 miles, and a wool blanket is like driving 83 miles.
I for one, am not going to give up knitting, but to justify the carbon footprint of producing the yarn I use, I am willing to cut down on paper towel use in my own little version of a carbon exchange program! And if I can bring myself to donate part of my stash to a local thrift store, that may satisfy some demand for yarn.
Laundering of knitted objects
To be comprehensive, we should also consider the carbon footprint of our knitting after the project is complete. Blankets, which were my inspiration for this analysis, are washed infrequently, but laundering would be relevant to knitted clothing items which are washed more. Common wisdom in the form of several websites that I found, claim that 80% of the carbon footprint of the garments come from laundering, including petrochemicals used in detergents and their production, clothes dryers and heating water.
When clothes are washed in hot water 90% of the carbon footprint is reportedly from heating the water alone. Hand-knits made from cotton or animal fibers can only safely be hand-washed in cold water using mild detergents and laid flat to air dry, which with the exception of the detergent, eliminates their laundering carbon footprint.
So which is better for the environment, cotton, wool or acrylic?
Cotton yarn has the least carbon footprint both in production of the fiber and in laundering. Considering just the carbon footprint of production, wool and by extension other animal fibers, have the highest carbon footprint. But when we consider the full life-cycle of a knitted object, including laundering, this may alter the conclusions for animal fibers from being the carbon footprint loser to being better than Polyester and Acrylics, which would be machine washed and dried. So in the case of wool and animal fibers we can truly say, “It will all come out in the wash.”
Additional sources:
https://www.fueleconomy.gov/feg/contentIncludes/co2_inc.htm (for the amount of CO2 generated from a gallon of gas)
https://medium.com/@ethitudeblog/youre-creating-most-of-the-carbon-footprint-of-your-clothes-without-even-realising-it-567a4350ae32