Polymer clay is easy to work with as it cures at a much lower temperature than natural clay. It comes in various colors and consistencies. It does not shrink or expand after it has been cured. It is also quite durable and waterproof.

Polymer clay is composed of polyvinyl chloride (PVC) and a plasticiser (salts, petroleum jelly).  

PVC is not biodegradable and can leach harmful chemicals, complicating waste management and recycling efforts. It is difficult to recycle due to additives and fillers that need to be separated.

If you like DIY, you can make a more sustainable alternative yourself. For this, you will need flour or cornstarch as a main component. You can check some recipes here.