BMW spent a lot of time and money developing the i3 as as green a car as could be reasonably done at the time given the original design goals...efficient, green, agile.
WHere leather is used, it is tanned using olive leaves rather than more toxic methods. The carbon fiber is sourced where there's hydro power so it doesn't depend on gas or oil fired generators. The 'fiber' areas like the front part of the dash is made from a plant fiber. 95% of the car is capable of being recycled when its end of life is reached. Wool is used in some trim levels because it wears well, is natural, comfortable, and sustainable versus vinyl that is oil based.
The carbon fiber frame is both strong and light, leading to lighter suspension pieces, leading to less weight it has to carry to move the occupants. The roof is made up of leftover carbon fiber scraps from making the body. The paint is water based so there are no VOCs. LED lights are used almost everywhere because they not only last longer, but use less electricity, helping maximize range. The wheels are forged which makes them both stronger and lighter so they use less material and improve the ride and range.
A little search will show you a bunch of YouTube videos on how the i3 was designed and built.