This is an interesting page;
https://blog.allplan.com/en/recycled-insulation-materials
"A sustainable building culture also looks for environmentally-friendly alternatives when it comes to insulation material.
That is why natural insulation material is enjoying increased popularity.
It is produced from renewable resources in a less energy-intensive process.
From an environmental standpoint, recycled insulation materials go a step further, which are 100% made from recycled material.
The energy consumption during their production is usually less than in the production of conventional insulation materials, which has a positive effect on their environmental footprint.
All of these insulation materials are characterized by their very good insulation properties.
Many are cheaper than the traditional options.
We will present tried-and-true materials for sustainable and environmentally-friendly insulation to you."