The broader TLRD is there's no market for gutter oil for cooking anymore when UCO sell more to industrial recyclers. Gutter oil for cooking in PRC, TW disapeared once waste cooking oil recycling industries sprung up. I think SKR avoided it all together by building biodesel management earlier.
Seriously though, what's the usual lifecycle for those waste oil tanks? Will the owner sell the contents to a recycler when it's full?