Undergarments are one of the most challenging clothing categories when it comes to sustainability. To start with, it's pretty difficult to find sustainable products in this category. While it's somewhat easier with bottoms, which can still contain synthetic materials despite being made of cotton, bras are a major problem because they consist of a range of different parts made from various materials. Cups are sometimes made of cotton, sometimes covered with synthetic lace, and the clasps and mechanisms for adjusting the straps are made of metal, sometimes even entirely of plastic. Undergarments cannot be purchased second-hand (well, technically, they can, but few people actually do that), cannot be donated, and are not the easiest to recycle because some recycling facilities refuse to process them due to fear of sanitary issues and/or the numerous parts made from different materials, and often they cannot be recycled due to the combination of synthetic materials they are made from.
Because of all these issues, it would be great to choose the most sustainable option from the get-go, which you can later recycle or compost when the garment reaches the end of its life. Ideally, you would choose organic biodegradable cotton that won't harm the environment when thrown in the trash. Some brands, such as Wolford, are experimenting with bioplastics, i.e., new types of compostable polyester made from corn or some other biomaterials. However, this technology is still in its infancy, and compostable undergarments made from such materials can still only be composted in industrial conditions.
Several brands already have pretty good solutions. Organic Basics have undergarments made entirely of organic cotton without any synthetic materials added to the blend, such as the Danish brand Organic Basics or French Ysé Paris. Others ensure that they only add elastane to the waistband so that it can be cut off and properly disposed of when the garment reaches the end of its life, and the bottom part, which is made entirely of organic cotton, can be safely recycled or composted. Such pieces can be found in the British brand Rapanui. It's quite important to disassemble a garment before recycling it. Do it whenever you can – cut off the metal rings from bras, and separate the elastic waistband or synthetic lace from the cotton part. This way, you will be at least somewhat certain that the garment will be recycled, or that the parts that are capable of breaking down in nature will do so.
In case I haven't emphasized this enough, I just want to point out that there is no perfect solution. Buying undergarments from certified sustainable brands can be quite expensive. Sometimes even Lidl can be a good choice if you've carefully read the label and checked where their cotton comes from. And if you're handy and own a sewing machine, you can get organic cotton and play around with designs yourself. Doing your best, taking small steps, and being aware of nature and the people around you is the best way to go.
The cover photo is from Organic Basics.