Pet Food, Liquid nitrogen, Water purifier, Beacon.?

In my workshop a have Pet Food, Liquid Nitrogen, Water Purifier and Beacon, but I dont need to use them... pet food is to feed animals-what animals? I dont have any... Liquid Nitrogen is used to scare monsters but what monsters Did not see any... Water purifier and Beacon are needed to clean stuff, but I did not need them and I cleand the whol island.. So Will thouse things get in use or what?