come up with ultra cheap tagging system for a sorting job

Hi, I am working on a small college project in which I have to sort objects of different materials (glass, plastic, metal, and paper) into different bins in an automatic fashion. I was thinking of using some sort of passive tagging system that is very cheap and doesn't need to store any data except that it can be categorized into 4 different types, because we are trying to sort 4 different types of materials. For example, we can associate each tag to one particular material type ( tag#1=glass, tag#2=plastic, tag#3=metal, and tag#4=paper) then if our object is made of the glass we stick tag#1 on it in which later can be detected by a reader and can be directed into glass bin. I was thinking of using some sort of ultra cheap DIY radio tags in order to be used for tagging each object and then read those tags using a reader and then sort them into different bins. I need a expert who can guide me through this sorting project who can give me advice and provide me with a feasible tagging solution that is flexible, ultra low cost and is commercially available since I am trying to build this system for my final presentation. I am planning to be able to buy the necessary equipment and eventually build it using an arduino. Initially I was thinking of passive RFID tags but I am not sure if it is viable option or not, since my target cost for each tag is only few cents (I want each tag to cost less than 5 cents). Is it possible to make home-made RFID tag without any IC? I know there are chipless RFID tags but they are not commercially available for purchase right now, thus I cannot use them. Or once somebody told me that I can make 4 different LC tank circuits that can oscillate at 4 different frequencies, therefore I can make a system in which oscillating frequency can be detected by some sort of reader. in this way I can print one type of LC tank (that correspond to certain frequency) on my object and detect which object is what. I am not sure if this is even possible since it was my first time hearing about LC circuits. I am looking for an expert who has a low cost and bright idea. I might even end up outsourcing the implementation and building the prototype as well. thanks