Google Scholar, Scopus, ScienceDirect etc. will provide peer-reviewed articles written by scientists with all the details. Google Scholar gave 771 000 results.
Quote from https://www.sciencedirect.com/science/article/pii/S1877705813004414:
" Nonetheless, there are other problems...
I will not put diesel I make from waste oil in my moden diesel car. Maybe in an ancient tractor. I have a PhD in chemistry. I had a masters student doing such experiments in the lab. One need more than just an estrification reaction to achieve quality fuel. This is not only my opinion...