Can someone explain me how to recycle cotton and polycotton (Cotton and polyester) fabric in an industrial process?

A friend of mine runs a fabric company, produces a lot of pre consumer waste (Leftover fabric) and he basically throws them away and it is a huge waste, I have heard about recycling these leftover fabric but I have hard time understanding them because some websites and videos are leaving out certain things out, so I hope someone is able to explain me about recycling these leftover fabric in details, also would prefer to know the processes and the machines needed.