Abstract: This invention provides the market with low-cost retrieval of valuable used cooking oil to customer distribution centers, where a mobile production unit visits to create biodiesel fuel, which can be immediately used by customers to fuel their fleet. In some variations, a method comprises identifying a network of customer distribution centers, collecting used cooking oil transported from users to customer distribution centers, providing a mobile reactor to convert used cooking oil into biodiesel fuel under effective reaction conditions, producing biodiesel fuel on-site at the customer distribution centers, and introducing the biodiesel fuel, directly or via a fuel blend, into fleet vehicles. Related systems and apparatus are also disclosed. This invention provides a clean source of energy from waste, a lower-cost alternatives to petroleum-derived diesel fuel, and improved environmental footprints including lower fuel use and lower total carbon emissions.