There’s a cool blog post about rack-mount hydroponics.
Someone got an extra 42U server rack and decided to try to grow lettuce in it. They documented the process.
I love the conclusion at the end of the post:
all that said, if you actually just want to grow stuff, you should probably not do any of this. this is not a serious guide and there are better approaches out there. but you do you. i had my fun with it, learned some things about hydroponics, and ate some delicious salads along the way.