Thanks a lot, I will search a bit about ESD and how to properly protect all the electronics.
As for the sleep mode, yes that was actually the idea and my friend doesn't want IoT functionality, he just wants to read the weight when he needs (so we were thinking about an LCD screen that powers up with a button and display the weight).
Also, I think we will need a way to turn on the Arduino whenever he starts putting cereals in the silo (either automatically or with a button). Then, we will connect a small alarm or a light to the Arduino so that my friend can easily see when a certain weight is reached (e.g 3000kg of cereals). Sorry if I didn't mention all these things in original post.