I found two uses for TC4, at least temporarily.
First, as a poor man’s TC11 before I could use TC4 as Gryphonknight suggested
Second use I found accidentally, when I moved my old bank (maybe a month worth?) to TC11, it took a while, because I had to earn the food to add as I moved recruits over.
Part way through this I was getting ready to do the second ascensions on my first group of 5 heroes, all about the same time needing 132k food each, and I was sooooooo food broke, so I took a step backwards–moved some surplus from my TC11 bank back to the old TC4 bank. Just so I could pull enough food out to ascend somebody, and not have to wait a day. Further, I was full-up on feeders and needed to ascend so I could level up and clear out space.
I think I’m finally over that hump; I haven’t needed to do it for a bit, but I do know that if I desperately need some food NOW, I can switch the TC I might use at 1 or 2 over to 4, and load it up from the bank.
Once I get a queue going at TC13 (or TC20), and get it loaded up as a food bank, this use will go away as well.