I've been using homemade laundry detergent for years. It doesn't harm the clothes, it doesn't leave a residue on clothing, and it has done no harm to my washing machine. As for encouraging the growth of bacteria--how? Most of the ingredients in my DIY laundry soap are antimicrobial. My recipe has homemade coconut castile soap, washing soda, borax, baking soda, and dollar store oxygen cleaner ("Oxi"). The oxygen cleaner is used to sanitize utensils, buckets, and bottles for beer or wine making so there's another negative for encouraging the growth of bacteria. There's no difference between liquid and dry homemade laundry soap. The liquid is made by adding water to your powdered laundry soap and just ends up taking up more room. One or two tablespoonsful of the laundry soap is all I need for an entire load. For about $40, I make about a year's worth of it for the two of us. My basic recipe has one pound of every ingredient in it. I have used more soap experimenting with it, but more soap doesn't seem to do anything except make more suds.