I have an ant problem in my house, specially in the kitchen, where they seem to have taken over. Just found out that they have cut through the plastic packaging of some food items and gotten inside. Is there a non-toxic pesticide or repellent I could use to drive them away? I have used turmeric powder before, and it is kinda effective, specially if you make a paste and stick it where the ants enter from. But I'd prefer not getting turmeric everywhere, and since I can't exactly find out where the ants are coming from, it wouldn't be as effective anyways.
You should try boric acid. Yes, it is an acid, but it is safe enough to be used as an eye wash for medical purposes. It is also toxic to ants and safe to use around the kitchen. I'm not sure if you consider it sustainable or not, but mixed with powdered salt or sugar, it gets rid of ants quite effectively.
I'm not quite clear on what you mean about non-toxic in the question. Do you mean non-toxic to ants or to people and pets?
There are several products on the market that use mint oil such as this one. While I haven't used the one linked, I have used ones sold at home depot branded as "safer" and they worked well. I sometimes had to do multiple applications over time, but in the long run, the ants subsided. In my case, I had sugar ants.
I had tried Lemon juice spray on Ants and it worked well.
I used un-fresh lemon and squeezed its juice into spray-can containing water and sprayed it on ants. On next days, ants weren't there!
There are electromagnetic ant repellents. Ants cannot stand the waves emitted by these devices. The device can be plugged into the wall socket. This is safe, harmless to humans and pets, noiseless, clean and hygienic. Energy consumption is about 5W.
These devices are sold at many places. Unfortunately there is no irrefutable scientific evidence of their effect.
What I personally tried is boiling about 5 lit water in a big pot and pouring this 100 C hot water into their hole. Unfortunately it works only outside. A bit primitive, but effective.