Shortly after my studio building was built I went looking for a 55 gallon drum. The nearest source was a local bakery which sold various containers when they were emptied. I had the help of one of the employees when picking out a drum. He suggested a specific one and pointed out that it had not been cleaned and still contained about five gallons of linoleum acid grease. He said was great grease, restaurant quality (edible) and would work well as an industrial grease. I brought it home and cleaned it and, sure enough, filled a five gallon bucket and several quart jars.
It was a messy job but it has supplied all the grease I’ve very needed and still have five gallons of the stuff. Perhaps I should look into starting a biofuel business.