My brushes are very environmentally friendly.
Bamboo is one of the more renewable plants. Most of my bamboo comes to me by way of Craigslist ads i place where i offer to clean up bamboo around a house. Usually the bamboo has not been touched in years. The owner of the bamboo gets their bamboo cleaned out and transformed into a work of living art. I get a trailer full of bamboo and often a sore back.
Many of my more exotic brush bristle materials were at one time in the past a small part of someone else’s trophy. I find some of the materials by way of estate sales where i buy a hide, a shawl or similar and transform it into many high quality, and one of a kind brushes.
Some of the bristle material i use, such as goat hair, as example, is collected by way other people who prepare the materials for other applications. The goat hair i use is cleaned and prepared for use as makeup brushes. No harm comes to the goats, beyond receiving a haircut.
My manufacturing is also environmentally friendly. Bamboo dust from cutting and sanding is the biggest byproduct and all of it recycled.