Nov 22, 2010When people think of RFID temperature sensors and the American food supply, they think of monitoring the cold chain. But before food crops can be shipped to market, they must first be grown. And a critical element of that growth process for fruits, vegetables, nuts and berries is pollination. No pollination, no crop—it's that simple.
The U.S. food supply chain depends on honeybees to perform the pollination. Two and a half million colonies of honeybees pollinate the nation's crops. Each spring, one and a half million of these colonies are trucked from locations across the United States to California's almond groves, in order to provide pollination services. From there, they are moved up and down the West Coast and across the country, pollinating a large percentage of the crops in those areas as well. Without pollination services, our fields and orchards would be barren.
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But honeybees are in trouble. Every year, more than one-third of the commercial colonies die—some owing to Colony Collapse Disorder (CCD), and some to other causes. Beekeepers can raise replacement colonies from those that remain, but at a cost: Removing bees from an existing colony weakens it, and new colonies are not as productive as those already established. As a result, some beekeepers have gone out of business over the past few years, and pollination fees have skyrocketed.
So, what is to be done? The answer lies in using RFID sensors to track what we call the hot chain—that is, conditions inside the hive. Here's how it works:
Honeybees have two major tasks. One is gathering food, and incidentally pollinating the blossoms upon which they forage for pollen and nectar. The other is raising more bees. Foraging is a decidedly dangerous task, with foragers living for only a few weeks, thereby necessitating a constant supply of replacements. The new honeybees are raised in the colony's brood nest, the size of which is the best single measure of colony health. Currently, beekeepers must open each hive to inspect the brood nest within—a step that beekeepers often skip, as it not only is time consuming and laborious, but also disturbs the bees.
What would an RFID sensor network that monitors colony health look like? Bees raise their brood in frames of honeycomb; there are eight to 10 frames in a hive body, and one or two hive bodies within a hive. Depending on the precision of monitoring desired, anywhere between one and 5 sensors per frame will suffice, resulting in a total of eight and 100 sensors per colony. Each hive might have its own RFID reader to aggregate the data and forward it to a local server, which would then pass that information along to the beekeeper's PC, or post it to a secure Web site, for further processing and display.
This system, then, can inform the beekeeper of each colony's health, as well as when and where intervention might be needed, and what to expect when opening the hive.
An RFID sensor network is a must-have for this application. First, beehives are often placed in agricultural locations, remote from electric power and communications lines. A wireless network with its own power supply, such as solar-rechargeable batteries, is a requirement for such sites, as is a cellular (or possibly radio) communications link. Second, beekeepers must be able to freely manipulate the frames of brood comb. Attaching wired sensors to the frames is a non-starter—only a wireless sensor will do. Third, the sensor must be very thin, and preferably small. A passive sensor might be best for this purpose, though a thin active sensor with at least a three-year lifespan would also be acceptable. Again, an RFID sensor appears to be the only option. Fourth, beekeepers often move frames from hive to hive in order to maintain balance. The ID part of the RFID sensor network would permit the frames to be moved from one hive to another, as it would capture the ID number of each frame within each hive.
Commercial beekeepers presently tend to be one of two types: either large commercial operators that supply thousands of mobile colonies for pollination, or part-time beekeepers that may keep bees in several widely scattered locations, but do so year-round. Both types can benefit from monitoring brood nests with an RFID sensor network. Large commercial operators can expect to reduce colony losses, while simultaneously reducing inspection time, and part-time beekeepers can share data with others located in the same geographic area, to provide insight into locally optimal beekeeping practices.
Frank Linton is a beekeeper and engineer in the Washington, D.C., area. He can be reached at
frank.linton@post.harvard.edu.
