It is possible to scan large numbers of bags simultaneously. I would recommend placing a tag on the outside of each bag. That would eliminate the requirement of finding and removing the tags at a later date, while also preventing them from being damaged and enabling you to reuse them.
Grain has a relatively low impact on RF energy in the UHF area of the spectrum (unless it is wet, in which case the liquid will absorb the energy). But keep in mind that reading tags through a large amount of almost any material can lead to some energy being blocked, which would mean the signal from the tag might not be strong enough to reach an RFID reader. As such, if you have a bag of grain at the bottom of a large pile of bags, you might not be able to read its tag.
Regarding case studies, we published an article about a similar project from Monsanto that involved tracking bags of specialty seeds (see Monsanto Hopes to Sow Benefits by Tagging Seed Packets). The company has maintained a low profile since that pilot was launched, but I do believe the results were positive. William Schulz, the firm’s global supply chain continuous improvement/optimization lead, spoke at our RFID Journal LIVE! event a few years ago (our next such conference will be held next week in Orlando, Fla.). Here is a recording of that presentation: http://www.rfidjournal.com/videos/view/60.
Almacafé deployed an RFID system in 2007 to monitor specialty coffee throughout its internal supply chain, from farms to warehouses, and during processing and bagging for export to roasting and trading facilities. The company tagged burlap bags of coffee beans so they could be tracked, then placed tags with clips on the bags. This project won our 2010 RFID Journal Award for Best Use of RFID in a Product or Service (see 2010 RFID Journal Award: RFID Helps Ensure That Special Cup of Joe).
And Adani Grain Logistics, which operates several grain-storage facilities throughout India, has implemented an automated, RFID-based system for receiving, testing and tracking food grain harvested in the states of Haryana and Punjab. The solution was tested in April 2007, and was deployed permanently three months later at two grain depots, located in the cities of Kaithal and Moga (see RFID Facilitates Grain Storage in India).
These projects show that tracking grain using passive tags is, in fact, feasible.
—Mark Roberti, Founder and Editor, RFID Journal
How Can I Use Your RFID Wizard to Get a Quote? »